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Cambrian Explosion Biological Big Bang Pix “Blink of An Eye” Eyesight Evolution:
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In The Blink of an Eye by Andrew Parker.

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DESCRIPTION: Illustrated hardcover w/dustjcket. Publisher: Perseus Publishing; (2003). Pages: 316. Size: 9¼ x 6¼ x 1¼ inches; 1½ pounds. Summary: Half a billion years ago, after a long, dark era, there was a sudden and great flourishing of life. The reasons baffled even Darwin, and every attempt to explain it since has failed; until now. H.G. Wells’s famous dictum, “In the country of the blind, the one-eyed man is king”, tells us something that may seem self-evident: sight matters. But imagine for a moment that the country of the blind is in fact the whole world, 550 million years ago. It’s a world where life is primitive and aimless, and evolution slow and painstaking.

Then something remarkable happens. Over the next five million years the process of evolution kicks into overdrive. Both hunters and prey develop armaments and defenses. And in this short space of time, “in the blink of an eye” in geological times, the number of different classifications of animals, “phyla”, mushrooms from three to thirty-eight, the number we still have today. The “when” and the “what” of this extraordinary event, known as the “Cambrian Explosion”, have been known for some time, and were made famous by Stephen Jay Gould’s bestselling book, “Wonderful Life”. What has, until now, been speculation is the “why”. Why did this “big bang” of biology happen when it did. What caused it?

Here for the first time Oxford Zoologist Andrew Parker reveals his theory of this great flourishing of life. Parker’s astounding explanation if that it was the development of vision in primitive animals that caused the explosion. Precambrian creatures were unable to see, making it difficult to see friend or foe. With the evolution of the eye, the size, shape, color, and behavior of animals was suddenly revealed. Once the lights were “turned on”, there was enormous pressure to evolve hard external parts as defenses and clasping limbs to grab prey. The animal kingdom exploded into life, and the country of the blind became a teeming mass of hunters and hunted, all scrambling for their place on the evolutionary tree.

CONDITION: NEW. New hardcover w/dustjacket. Basic Books (2003) 352 pages. Unblemished except for faint edgewear to dustjacket and covers. Pages are pristine; clean, crisp, unmarked, unmutilated, tightly bound, unambiguously unread. The edgewear consists of faint crinkling to the dustjacket spine head and heel. And by faint, we mean precisely that, literally. It requires that you hold the book up to a light source, tilting it this way and that so as to catch the reflected light, and scrutinize it quite intently to discern the faint shelfwear. Beneath the dustjacket the covers are clean and unsoiled, echoing only the same faint edgewear as the overlying dustjacket. Condition is entirely consistent with new stock from a traditional brick and mortar bookstore environment (such as Barnes & Noble, Borders, or B. Dalton, for instance), wherein new books might show faint signs of shelfwear, consequence of routine handling and simply the ordeal of constantly being shelved, re-shelved, and shuffled about. Satisfaction unconditionally guaranteed. In stock, ready to ship. No disappointments, no excuses. PROMPT SHIPPING! HEAVILY PADDED, DAMAGE-FREE PACKAGING! Meticulous and accurate descriptions! Selling rare and out-of-print ancient history books on-line since 1997. We accept returns for any reason within 30 days! #1755f.

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PLEASE SEE PUBLISHER, PROFESSIONAL, AND READER REVIEWS BELOW.

PUBLISHER REVIEWS:

REVIEW: An accomplished young scientist solves one of the greatest mysteries of evolution: What caused the dramatic explosion of life half a billion years ago? About 550 million years ago, there was literally an explosion of life forms, as all the major animal groups suddenly and dramatically appeared. Although several books have been written about this surprising event, known as the Cambrian explosion, none has explained why it occurred. Indeed, none was able to.

Here, for the first time, Oxford zoologist Andrew Parker reveals his theory of this great flourishing of life. Parker's controversial but increasingly accepted "Light Switch Theory" holds that it was the development of vision in primitive animals that caused the explosion. Drawing on evidence not just from biology, but also from geology, physics, chemistry, history, and art. “In the Blink of an Eye” is the fascinating account of a young scientist's intellectual journey, and a celebration of the scientific method.

Andrew Parker received his Ph.D. from Macquarie University in Sydney while working in marine biology for the Australian Museum. He became a Royal Society Research Fellow at Oxford University's Department of Zoology in 1999, and is a Research Fellow of Summerville College (Oxford) and a Research Associate of the Australian Museum and University of Sydney. He has published numerous scientific papers on topics as diverse as optics in nature, biometrics, and evolution. He has been named by the “London Times” as one of the three most important young scientists in the world for his work in investigating and answering the great riddle of the Cambrian explosion.

REVIEW: The Cambrian Explosion is universally referred to as biology's "Big Bang." About 550 million years ago, there was literally an explosion of life forms, as all the major animal groups suddenly and dramatically appeared. Why did it happen this way? Why didn't these creatures continue the slow, plodding pace of evolution, appearing only very gradually in the fossil record? Although several books have been written about this surprising event, none have explained why it occurred. Indeed, none were able to.

Here, for the first time, Oxford zoologist Andrew Parker reveals his theory of this great flourishing of life. Parker's "Light Switch Theory" holds that it was the development of vision in primitive animals that caused the explosion. Precambrian creatures were unable to see, making it impossible to find friend or foe. With the evolution of the eye, the size, shape, color, and behavior of animals was suddenly revealed for the first time. Once the lights were "turned on," all animals had to either adapt or die, and in a geological instant, the world became a very different place.

A controversial theory but one that is quickly gaining ground, the “Light Switch Theory” promises to revolutionize our understanding of life and light. Drawing on evidence not just from biology but also from geology, physics, chemistry, history, and art, in “The Blink of an Eye” is the fascinating story of a young scientist's intellectual journey, and a celebration of the scientific method.

REVIEW: Andrew Parker is a Royal Society Research Fellow at Oxford University's Department of Zoology. He has been named by the London Times as one of the three most important young scientists in the world for his work in investigating and answering the great riddle of the Cambrian explosion. He lives in Oxfordshire, England.

TABLE OF CONTENTS:

1) Evolution's Big Bang.

2) The Virtual Life of Fossils.

3) The Infusion of Light.

4) When Darkness Descends.

5) Light, Time and Evolution.

6) Color in the Cambrian?

7) The Making of a Sense.

8) The Killer Instinct.

9) The Solution.

10) End of Story?

PROFESSIONAL REVIEWS:

REVIEW: Oxford University zoologist Parker tackles one of biology's biggest mysteries in this non-technical account. He provides a relatively simple explanation for the sudden explosion of life forms that defines the boundary between the pre-Cambrian and Cambrian eras approximately 543 million years ago: "The Cambrian explosion was triggered by the sudden evolution of vision" in simple organisms. In Parker's "Light Switch" theory, active predation became possible with the advent of vision, and prey species found themselves under extreme pressure to adapt in ways that would make them less likely to be spotted.

New habitats opened as organisms were able to see their environment for the first time, and an enormous amount of specialization occurred as species differentiated. Parker claims that his theory is far more robust than previous attempts to explain the surge in diversity, even those most recently advanced by proponents of a snowball earth (the theory presented by Gabrielle Walker in Snowball Earth). In readable prose, Parker provides detailed information on the fossil record as well as a wealth of interesting material on the role light plays in environments and how vision operates across a host of species. Photos and line drawings. [Publisher’s Weekly].

REVIEW: The cause of the sudden appearance of major life-forms 540 million years ago, known as the Cambrian explosion, has been paleontology's biggest mystery and, next to the disappearance of the dinosaurs, it is most fascinating to onlookers outside the science. Within the discipline, a new solution to the enigma has been boldly advanced, offered here in popular form by its expositor. Oxford zoologist Parker proceeds methodically, explaining, for example, what a phylum is, a point crucial to his theory because, contrary to popular perception, most phyla existed before the Cambrian explosion, he maintains.

He believes that explaining the explosion means explaining the evolutionary advantages of organisms' external appearances, as discussed in the aptly titled “Wonderful Life” by Stephen Jay Gould. Building on Gould, Parker also revisits the celebrated Burgess Shale central to that book, emphasizing the evolution of the eye in terms of its ability to detect light. Something fundamental changed in the earthly intensity of light and then in prey-predator dynamics, avers Parker, whose clarity will thrill science fans, as will his revolutionary theory. [Booklist]

REVIEW: The Cambrian Explosion was one of the great mysteries of evolution. The sudden proliferation of life forms 550 million years ago baffled even Darwin, who, in “The Origin of Species”, admitted that such rapid diversification presented a valid argument against his theory. But now, a century and a half later, 34-year-old Oxford University researcher Andrew Parker advances a new explanation of the Cambrian Explosion so compelling that many prominent scientists have accepted its plausibility. Parker contends that it was the development of sight in animals that caused biology's Big Bang. His account of how he solved the problem of the origin of biodiversity unfolds with the excitement of a topnotch whodunit.

REVIEW: The Cambrian Period saw the first proliferation of complex life on earth. Parker presents the fascinating argument that the development of vision triggered “evolution’s big bang”. Parker’s conclusion, that the presence of eyes indicates the evolution of an active hunting lifestyle among Cambrian creatures is both convincing and surprisingly fresh.

REVIEW: Andrew Parker, an Oxford University zoologist, presents a broad audience treatment of his intriguing theory of vision as the on-switch for the Cambrian explosion in evolution. He assembles his intriguing argument like a meticulous zoological barrister, in the same manner as Charles Darwin. Parker makes a compelling case. It's a neat theory. I don't think you can find a more reader-friendly introduction to evolutionary biology.

REVIEW: We do have a well-written book, containing much really interesting science and a good strong hypothesis that will surely stimulate others to praise, to criticize and try to refine or replace. Parker's central argument certainly deserves careful attention, especially as it aims to provide a unique and hitherto unrecognized solution to one of evolution's most significant conundrums. A brilliant and eminently readable evolutionary detective tale. Parker's energy and intelligence are undeniable.

REVIEW: A bold and compelling theory...presented with clarity and subtlety. [Scotland on Sunday].

REVIEW: Parker's thesis is carefully presented, and reads like something of a mystery...A valuable and inventive contribution. [Providence Journal].

REVIEW: A brilliant and eminently readable evolutionary detective tale...[Parker's] energy and intelligence are undeniable. [Roanoke Times].

REVIEW: A well-written book, containing much really interesting science and a good strong hypothesis. [Washington Post].

REVIEW: An informative work...Parker makes a persuasive case that the Cambrian explosion was triggered by the evolution of vision. [Boston Sunday Herald].

REVIEW: I don't think you can find a more reader-friendly introduction to evolutionary biology. [San Jose Mercury News].

REVIEW: Parker makes a compelling case...It's a neat theory. [San Diego Tribune].

REVIEW: Parker provides an insightful glimpse into the mind of the scientist...[A] thought-provoking work. [Library Journal]

REVIEW: Parker's conclusion...is both convincing and surprisingly fresh...cutting-edge science, highly recommended. [Kirkus Reviews].

READER REVIEWS:

REVIEW: There have been living creatures on Earth for about four billion years, but most of that time they were blind. Most of that time, also, they were very simple (single cell animals, sponges, and soft-bodied animals). The famous Cambrian explosion was the sudden boom in animal diversity that happened between 543 and 538 million years ago. It is when teeth and armor appeared. It is also when eyes appeared. It is easy for us to imagine the drama of, say, the destruction of the dinosaurs 65 million years ago, but according to Andrew Parker the Cambrian explosion is "the most dramatic event in the history of life".

Other dramatic events have their explanations (an asteroid wiping out the dinosaurs, for instance), but there has not been a satisfactory explanation of the Cambrian boom. Until now, according to Parker, and he has come up with it. “In the Blink of an Eye” is a convincing explanation that he first announced seven years ago: the Cambrian explosion was caused by the evolution of vision. What happened in the explosion is that animals acquired armor, hard body parts, and a huge variety of different shapes. Parker explains that the shapes and armor came along because eyes came along. In the blind pre-Cambrian world, creatures took in sensation by smell, taste, sound, or touch.

It did not matter what the creatures looked like, because no other creature could see them. It didn't matter if creatures had no armor, because predators weren't chasing them. Creatures scavenged upon dead animals, but did not need claws or jaws to catch those; catching prey was unlikely for a creature that was blind, so predation was not the rule. And then there was light! Parker thinks that a soft-bodied ancestor of the trilobite was the first creature to get a light sensitive patch that eventually differentiated into different units of an eye. The trilobite that could gradually see better could gradually become a better predator.

Not only does vision power a diversity of the trilobite itself, into such skills as agility and efficient use of muscular propulsion, it powers changes in prey. In the dark, an animal has no need to care what it looks like. Pursued by creatures that can see, an animal has many avenues of change that it might follow, like making camouflage, developing its own armor, swimming faster, growing bigger, or gaining its own eyesight. And then the predators can become modified to overcome those tactics, and the familiar evolutionary battle is enjoined in earnest. Vision started diversity, and has powered it ever since.

Parker's book is a rich account of how he came to these conclusions, with a wide-ranging gathering of supportive evidence. He writes clearly, and with a witty understatement. When, for example, he describes examining seed-shrimps and dissecting them under the microscope, he says, "the seed-shrimps tend to roll around and fall in exactly the positions that are not required of them". Any scientific theory is open to question, and surely the very simplicity of Parker's explanation will make it a target for other theorizers with new data. Right now, though, in considering the Cambrian explosion, the “Light Switch Theory” is the way to see things.

REVIEW: What triggered the Cambrian Explosion? Starting around 543 million years ago, there was a 10-million year period (give or take 5 million years) in which the number of phyla on this planet went from three to thirty-eight. After that, no new phyla appeared. Something dramatic happened during that time period, but why? There was also a major evolution of external body parts in all phyla at that time, but what caused all this? There are some explanations that have been taken seriously for the Cambrian explosion, and Parker reviews a number of them.

The first is that the Cambrian was just a great time for rapid evolution. But there is evidence from embryos of non-skeletal animals that indicates that the Cambrian was probably not a particularly hospitable time after all. The second group of explanations that Parker deals with attempt to cover not only the Cambrian explosion itself, but the Precambrian changes in internal body plans. But Parker wants to know what caused the explosion itself, and feels strongly that the Precambrian changes are not an integral part of this.

The third explanation is that the physical environment changed significantly at the start of the Cambrian. That means changes in, say, oxygen, carbon dioxide, or phosphorus levels. But these levels changed at plenty of times, and the start of the Cambrian doesn't appear to be all that special. A fourth explanation is that shallow-water continental shelf areas increased at the start of the Cambrian. A fifth is that there was a "Snowball Earth" that ended just prior to the Cambrian. A sixth is that collagen was acquired by animals during the Cambrian. A seventh deals with the generation of new niches: perhaps the increased availability of free-swimming plants could create a new niche. An eighth deals not with niches, but with all feeding modes.

Yes, one or more of these explanations may be pretty close. But they don't satisfy Parker, and he has an explanation that makes plenty of sense, namely that around 543 million years ago, there was a sudden development of sight among animals. That means eyes, and brains to interpret the light that reaches those eyes. By the way, one of the early species to acquire eyes may have been the box jellyfish, which has no brain! But the trilobites are the creatures that Parker dwells on: they originated at the start of the Cambrian, and they appear to have had eyes (and brains) at that time.

The book covers plenty about what eyes are, what different sorts of eyes there are, how eyes evolved, and what eyes are used for. As an example, rabbits have eyes on each side of their heads. A reason is that they spend plenty of energy to avoid getting eaten. That means they want as close to 360-degree vision as they can get, since they intend to run away at top speed towards safety if they see a predator (and keep running for their lives if the predator chases them). That is a cost-effective idea! On the other hand, foxes spend more of their energy chasing potential food. They don't need 360-degree vision for this, so they have eyes in front, where they can be used to provide depth perception. That lets them judge the distances to possible prey and saves them from costly futile chases.

It doesn't take much imagination to, um, see that the introduction of vision could lead to a huge evolutionary explosion, as species developed armor, camouflage, and more defenses against suddenly non-blind predators. So this is indeed an interesting hypothesis. A critical issue is just how long it would take for working eyes to evolve from simple patches of light-sensitive cells (sandwiched between a transparent protective layer and a layer of dark pigment). But as the author explains, a paper by Dan-Eric Nilsson and Susanne Pelger shows that a few hundred thousand years should be ample time to accomplish all this. Vision could indeed have arisen in an evolutionary blink of an eye. And that may well have led to the Cambrian explosion.

At the end of the book, Parker considers possible triggers for the evolution of eyes, such as increases in the available light reaching the Earth's surface. I think these areas are worth pursuing as well. I thoroughly enjoyed this book, and I recommend it.

REVIEW: Biologist Andrew Parker's "In the Blink of an Eye", is a spirited, provocative statement of his "Light Switch" theory accounting for the dramatic burst in the evolution of metazoans (multicellular animal life) at the dawn of the Cambrian Period of the Paleozoic Era, approximately 543 million years ago. He makes a very persuasive case that it was the evolution of eyesight in metazoans which triggered a rapid adaptive radiation of metazoans, though confined mostly to arthropods (living representatives include shrimp, crabs, lobsters, spiders, and insects, to name but a few) as seen most impressively in the celebrated "Burgess Shale" fauna from approximately 515 million years ago.

Parker opens the book with a discussion of the Cambrian explosion and the nature of fossilization itself. Next he turns to the physics of light, and discusses how living animals use light not only for nourishment, but also as a means of defense, including, but not exclusively, mimicry to avoid detection by potential predators and prey. He also describes how sight has been lost by cave-dwelling animals, and the evolution of bioluminesence in deep sea creatures. Surprisingly, this leads next to exploring the possibility that Cambrian creatures were colorful, dressed in vibrant hues of many colors, which were quite visible in the shallow seas of the Burgess Shale fauna.

The final chapters describe the evolution of sight in metazoans, and Parker alleges that a primitive ancestral trilobite has been discovered in the uppermost occurrence of the Ediacaran (latest Precambrian) fauna with a pair of crude eyes. So why was sight necessary? Parker states that it arose as the direct consequence of some animals becoming active predators, the earliest trilobites, and this, in turn, triggered an evolutionary arms race in the development of body armor to defend from predation; which we see in the fossil record as the "Cambrian explosion".

Parker has made an elegant, persuasive case on behalf of his "Light Switch" theory to account for the Cambrian explosion. It is the most consistently logical explanation I have come across, supported amply by the evidence he has presented in this book. I recommend this book to anyone interested in paleobiology, or in general with evolution; especially those fascinated with the Cambrian explosion. Much to his credit, Parker has written a compelling tome which comes close to the literary eloquence attained by the likes of Stephen Jay Gould, Ernst Mayr and George Gaylord Simpson.

REVIEW: In this illuminating study Parker contends that light is the driving force behind evolutionary change. Light, he argues, is the most prevailing environmental element. Crossing biology, geology, ecology and physics with a bridge of optics, he shows how many body structures have varied due to light's availability and intensity. Most important to the reader, is his contention that when life developed a greater sensitivity to light, evolution was given a significant boost. We call the time of that "boost" the Cambrian Explosion.

According to Parker, the mechanism driving the boost was the evolution of the eye. The wide diversity exhibited by evolution's abrupt advances around 550 million years ago produced creatures whose descendants are cats, bears, birds, and you. Parker provides a wealth of background material in developing his thesis. The forces of plate tectonics, the way light is absorbed, reflected, bent, and even biologically generated are all presented. He shows the relevance of each aspect in a slowly and carefully built concept.

Parker presents his theme with verve. "Let there be images!" is a concluding example. New ideas in science tend to use a forceful approach. Since he's laid a firm Darwinian foundation for this exclamation, perhaps his enthusiasm is warranted. He explains much about early life, the nature of light and how animals have adapted body plans to use light effectively.

Parker shows how new research tools can analyse fossils to reveal the past wasn't the soft, dull, colorless world often portrayed. Some of the tricks developed by Nature millions of years ago weren't duplicated by human technology until very recently. Light, he explains, was both an attractant and a repellent in the shallow seas of early oceans.

The mortar binding the facets of Parker's idea is predation. Both eaters and eaten needed to detect each other to survive. In parallel with the eye, bodies changed to avoid detection and deflect biting mouths. Survival in evolutionary terms, he reminds us, means more than eating or avoiding being a meal. Vision enhanced the process of sexual selection, with the new body forms exhibiting colors to attract mates.

These and other factors combine to provide what Parker calls his "Light Switch" view of the Cambrian period. This step is taken to grant eye evolution a rapid pace in line with the many changes the Cambrian Explosion seems to evidence. Parker's ebullient prose is supplemented by excellent line drawings and photographs. These provide both background and examples of his points. His style, while ardent, is a bit rambling, although this can be forgiven in a book covering so many aspects of evolution's path.

Read this book, reflect on Parker's ideas, and remember there are other proposals for the cause of the Cambrian Explosion equally well presented.

REVIEW: This book is worth the time to read. It is a treasure trove of examples of evolutionary development, of environmental pressures and opportunities, and of the cumulative effects of natural selection on the development/evolution of light sensitive organs and eyes. It's a great counter to the Intellegent Design/Creationist view that complex things/organs can't have evolved.

The complexity of the eye has long been used by Creationists as an example of an organ that would fall apart if any part were missing. Well this book shows very well the myriad of evolutionary solutions to the environmental pressure of the presence of light, from very primitive to very complex organs of vision.

Mr. Parker shows the great range of ways, the multiple evolutionary paths of light sensing organs, some with lens, some without, some with an iris, some without, some with a single eye, some with multiple eyes. It should be mandatory reading (along with Dawkins' "The Blind Watchmaker" for those who give up on exploring and understanding nature if it's complex, throw up their hands and say, "It's too complex. It must be from Intelligent Design."

This is a very good exploration of some of that complexity in a naturalistic framework, i.e. a scientific framework.

REVIEW: Often, it is creationists who have enjoyed using the Cambrian explosion as evidence that Darwin's theory of evolution was somehow off the track, yet, Oxford zoologist Andrew Parker has put forth what is likely the most plausible explanation of this great event in evolutionary history.

It is known throughout scientific circles that 543 million years ago there were 3 or 4 Phyla in the animal kingdom. Around 5 million years later, 538 million years ago, we had 38 Phyla in existence. Parker makes a very powerful argument that during this time, many creatures began developing hardened shells of armor. Why was this? What was the change in the environment in which these animals survived, that would require hardened defensive armor?

Parker argues, and I have seen few rebuttals to counter his ideas, that in the pre-543 million years ago period, also known as the Pre-Cambrian, that there there is no fossil evidence of any kind supporting the evolution of eyesight and little in support of exterior armor and exoskeletons. Parker agues that during the 5-10 million years after Pre-Cambrian Period, that the light sensitive organelles on their bodies evolved into compound eyes, allowing predators limited and rudimentary eyesight and sensing abilities.

To survive the onslaught prey species developed the armor needed to defend themselves from those with vision, and the explosion of new Phyla rocketed and accelerated like never before, in a very short time period (5-10 million years)...in the blink of an eye. Yes, according to Parker, it is eyesight and the evolution of it, which caused the Cambrian explosion of phyla.

REVIEW: When one thinks of prehistoric life, the first thoughts to come to mind are often dinosaurs, then maybe wooly mammoths and cavemen. But prehistoric life extended farther back, and one of the most intriguing periods is the Cambrian Period when the diversity of animal life exponentially increased. This "Cambrian Explosion" is one of the most studied aspects of prehistoric life, and its origins are one of biology's greatest questions.

This book answers the question by showing how the development of vision, that is the evolution of the eye, dramatically changed life on earth. The author comes to this answer as someone would piece together a puzzle, one piece at a time. Each piece is one chapter of this book. Some of the pieces include an explanation of how eyes and vision work, a study of color and its importance in ecosystems and the survival of individuals and species, a comparison of different ecosystems and how the amount of light in each one has affected evolution, and a review of life's evolution, covering both known and unknowns.

Over the course of this book, the author very clearly and objectively shows that the development of eyes, sensory organs that could identify and locate objects, was the spark that accelerated the rate of species diversification and the onset of numerous external features such as skin color, teeth, spikes, horns, etc... All in all, a great work of science.

REVIEW: Parker's book was extremely interesting. As a geologist, I was delighted to find a book that was not completely bogged down with scientific terminology, so that I could pass this book on to my friends and family and share my interest. For someone who is not a geologist or biologist, a few of the terms may be a bit heavy. However, I believe for any science, paleontology or geology geek, this book is a must-read. The exploration of the Cambrian life forms is fascinating. The chapter on eyes alone is amazingly informative and very interesting. The reader will be swept away by Parker's enthusiasm and honesty. Especially enjoyable were his description of the male seed shrimp's attempts to court a female, and the descriptions of the predators and prey of the Cambrian. I have become enamored of Trilobites after reading this book, creatures I had previously not given a lot of thought.

REVIEW: Imagine what it must have been like to be the first creature that had eyes, that could see through the murky waters. The world is no longer just what you touch, or what chemicals drift your way. Now you can range widely to hunt for food, and your dinner can't even see you coming! From an evolutionary perspective, this must have been the nuclear scenario for many species, and the true start of the evolutionary arms race.

This is Andrew Parker's thesis, presented for a general audience. At times, you might feel like he's belaboring his points, but long before the end of the book you'll wonder why something this obvious never occurred to you. On the way you run into some unique characters, some mysterious creatures, and get some fossil-digging history too. Very interesting and easy to read.

REVIEW: The author summarizes the story of pre-Cambrian evolution insofar as it is known and considers possible causes for the evolutionary changes that define the Cambrian. He concludes that the key event was the rapid simultaneous evolution of vision, predation, and protective structures as a consequence of improved environmental light levels. The book is an essential read for anyone interested in the Cambrian period or the story of evolution.

REVIEW: The story of how sight evolved 540 million years ago and what it did to fauna and flora of the earth. Unbelievable that life forms could not see before that time. This is an excellent book, well put together and researching subjects other that those outlined in the book. An excellent buy which will amaze you and keep you reading. This book is a 10+ and recommended to buy.

REVIEW: A very interesting theory, well documented and argued. You will enjoy reading it as Andrew Parker makes it interesting connecting the dots between life as we know it and the Cambrian Explosion. There are actually well founded theories that explain why life diversified suddenly 543 millions years ago. No need of supernatural being for that. Now is it the final answer for that mystery? I doubt it, but it is up to you to decide.

REVIEW: "In the Blink of an Eye" splits the Cambrian Explosion into two pieces, the development of multi-cellular life (the "Precambrian surge") and the evolution of "hard parts" as a result of the development of vision (which is the bulk of the book). There is a lot of support for his main conclusion. The book is very up-to-date and worth reading.

REVIEW: This book's theory is attractive enough that many experts ought to feel embarrassed that they didn't propose it earlier. It's not so much that people looking at the Cambrian explosion should have seen the evidence pointing to this theory - the book tends to indicate that some important pieces of evidence were only found in the last decade or so.

What puzzles me is why nobody modeled the effects of the evolution of eyesight well enough to decide to go looking for the results in the fossil record. This makes me wonder whether a lot of experts are still uncomfortable with the punctuated equilibrium model of evolution.

REVIEW: Parker presents a very plausible theory that seems to explain the great increase of species in the Cambrian explosion. In fact, it is so well-presented (much like Darwin included overwhelming arguments and examples in “Origin of Species”) that you are tempted to repeat Huxley and say that it is so obvious, why didn't I think of that?

REVIEW: The content of this book is simply fascinating. Not only does it present a plausible solution to the Cambrian enigma, it also provides a huge amount of information on the role of color and eyesight in nature.

REVIEW: Parker's book is an entertaining and surprisingly broadly informative read. Few paleontologists, I think, would disagree with the idea that the development of vision (as distinct from mere light sensitivity) gave an enormous acceleration to Early Cambrian evolutionary rates.

REVIEW: Really interesting theory. Definitely worth a read. It, however, brought up a bunch of other questions that I now want answers to.

REVIEW: I am enjoying the book! Mr. Parker is making me think. A good read.

ADDITIONAL BACKGROUND:

PALEO SCIENCES: Paleontology and Related Sub-Specialties:Paleontology is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene Epoch. That's roughly 11,700 years before the present. The discipline includes the study of fossils so as to classify organisms, as well as the study of interactions between those organisms and their environments. The latter is a subdiscipline oftentimes referred to as observations have been documented as far back as the 5th century BC. The science became established in the 18th century as a result of Georges Cuvier's work on comparative anatomy. It then developed verely rapidly in the 19th century. The term itself originates from Greek “palaios”, meaning old or ancient, and “ontos", meaning being or creature, and “logos”, meaning speech, thought, or study".

Paleontology lies on the border between biology and geology. It differs from archaeology in that it excludes the study of anatomically modern humans. It now uses techniques drawn from a wide range of sciences, including biochemistry, mathematics, and engineering. Use of all these techniques has enabled paleontologists to discover much of the evolutionary history of life, almost all the way back to when Earth became capable of supporting life, roughly over 4 billion years ago.

The simplest definition of paleontology is "the study of ancient life". The field seeks information about several aspects of past organisms including their identity and origin, their environment and evolution, and what they can tell us about the Earth's organic and inorganic past. William Whewell (1794–1866) classified paleontology as one of the historical sciences, along with archaeology, geology, astronomy, cosmology, philology and history itself

Paleontology aims to describe phenomena of the past and to reconstruct their causes. There are three main elements to this objective. First is to describe past phenomena. Second is to develop a general theory pertaining to the causes of various types of change. Last to apply those theories to specific facts. When trying to explain the past paleontologists and other historical scientists often construct a set of one or more hypotheses about the causes. They then look for a "smoking gun".

A “smoking gun” is evidence that strongly accords with one hypothesis over any others. Sometimes researchers discover a "smoking gun" by a fortunate accident during other research. For example in 1980 researchers discovered iridium in the Cretaceous–Tertiary boundary geological layer. Iridium is principally an extraterrestrial metal. This discovery made an asteroid impact the most favored explanation for the Cretaceous–Paleogene extinction event, though there is still debate pertaining to the possible contribution of volcanism to the extinction.

As opposed to proving hypotheses about the workings and causes of natural phenomena, a complementary approach is oftentimes employed by conducting experiments to disprove hypotheses. Although this approach cannot prove a hypothesis, the accumulation of failures to disprove is often compelling evidence in favor of a hypothesis.

As knowledge has increased paleontology has developed specialized sub-divisions. Some of these sub-disciplines focus on different types of fossil organisms while others study ecology and environmental history, such as ancient climates. The latter specialty is known as “paleoclimatology”. Body fossils and trace fossils are the principal types of evidence of ancient life. Geochemical evidence has helped to decipher the evolution of life before there were organisms large enough to leave body fossils.

Estimating the age of these remains is essential but can be difficult. Sometimes adjacent rock layers allow radiometric dating, which provides absolute dates that are accurate to within 0.5%. More often however paleontologists have to rely on relative dating by solving the "jigsaw puzzles" of biostratigraphy. Biostratigraphy refers to the arrangement of rock layers from youngest to oldest.

Classifying ancient organisms is also oftentimes difficult. Many ancient organisms do not fit well into the Linnaean taxonomy system scientists use to classify living organisms. Paleontologists more often use “cladistics” to draw up evolutionary "family trees". The final quarter of the 20th century saw the development of molecular phylogenetics. This discipline investigates how closely organisms are related by measuring the similarity of the DNA in their genomes.

Molecular phylogenetics has also been used to estimate the dates when species diverged. However there occasionally exists some controversy regarding the reliability of the molecular clock on which such estimates depend. Though paleontology lies between biology and geology since it focuses on the record of past life, nonetheless its main source of evidence is fossils in rocks. For historical reasons then paleontology is part of the geology department at many universities.

In the 19th and early 20th centuries geology departments found fossil evidence important for dating rocks. Campus biology departments on the other hand showed comparsatively little evidence on fossil-bear rocks. Paleontology also has some overlap with archaeology. Archaeology primarily works with objects made by humans and with human remains. Paleontologists on the other hand are interested in the characteristics and evolution of humans as a species.

When addressing evidence about humans archaeologists and paleontologists may work together. For example paleontologists might identify animal or plant fossils around an archaeological site. This aids in the determination of what hominid populations inhabited the area and what they ate. This research might even analyze the climate at the time of habitation. In addition, paleontology often borrows techniques from other sciences, including biology, osteology, ecology, chemistry, physics and mathematics.

For example geochemical signatures from rocks may help to discover when life first arose on Earth. Analyses of carbon isotope ratios may help to identify climate changes and even to explain major transitions such as the Permian–Triassic extinction event. A relatively recent discipline, molecular phylogenetics, compares the DNA and RNA of modern organisms to re-construct the "family trees" of their evolutionary ancestors. It has also been used to estimate the dates of important evolutionary developments.

Techniques from engineering have been used to analyze how the bodies of ancient organisms might have worked. Examples would include a determination of the running speed and bite strength of Tyrannosaurus Rex. Another example would include the flight mechanics of Microraptor. Analyses using engineering techniques showed that Tyrannosaurus had a devastating bite. The same techniques raised doubts about its running ability.

It is also relatively commonplace to study the internal details of fossils using X-ray microtomography. Paleontology, biology, archaeology, and paleoneurobiology combine to study endocranial casts (endocasts) of species related to humans to clarify the evolution of the human brain. Paleontology even contributes to astrobiology. Astrobiology involves the investigation of possible life on other planets. Paleontology aids in this investigation developing models of how life may have arisen, and by providing techniques for detecting evidence of life.

Again as knowledge has increased, paleontology has developed specialized subdivisions. Elaborating on our earlier mention of this topic, vertebrate paleontology for example concentrates on fossils from the earliest fish to the immediate ancestors of modern mammals. On the other hand invertebrate paleontology deals with fossils such as molluscs, arthropods, annelid worms and echinoderms.

Further elaborative examples would include Paleobotany. Paleobotany studies fossil plants, algae, and fungi. Micropaleontology deals with microscopic fossil organisms of all kinds. Palynology is the study of pollen and spores produced by land plants and protists. This specialty straddles paleontology and botany. It deals with both living and fossil organisms.

Instead of focusing on individual organisms, paleoecology examines the interactions between different ancient organisms. This would include for example their food chains and two-way interactions with their environments. For example the development of oxygenic photosynthesis by bacteria caused the oxygenation of the atmosphere. This in turn hugely increased the productivity and diversity of ecosystems. Ultimately this led to the evolution of complex eukaryotic cells, from which all multicellular organisms are built.

Paleoclimatology although sometimes treated as part of paleoecology focuses more on the history of Earth's climate. Included in this focus are the mechanisms that have changed Earth's climate. This would include evolutionary developments. For example the rapid expansion of land plants in the Devonian period removed more carbon dioxide from the atmosphere. This had the effect of reducing the greenhouse effect. In turn this helped to cause an ice age in the Carboniferous period.

Biostratigraphy involved the use of fossils to aid in the determination of the chronological order in which rocks were formed. Biostratigraphy is useful to both paleontologists and geologists. Biogeography studies the spatial distribution of organisms. It is also linked to geology as it aids in explaining how Earth's geography has changed over time.

Fossils of organisms' bodies are usually the most informative type of evidence. The most common fossil types are wood, bones, and shells. Fossilization is a rare event to begin with. Then most fossils are destroyed by erosion or metamorphism before they can be observed. Hence the fossil record is very incomplete. This is increasingly so as science moves further and further back in time. Nonetheless the study of fossils is often adequate to illustrate the broader patterns of life's history.

There are also biases inherent in the fossil record. Different environments are more favorable to the preservation of different types of organism or parts of organisms. Furthermore only the parts of organisms that were already mineralized are usually preserved. An example would be the shells of molluscs. Since most animal species are soft-bodied they decay before they can become fossilized. As a result although there are over thirty phyla of living animals, two-thirds have never been found as fossils.

Occasionally unusual environments may preserve soft tissues. This allows paleontologists to examine the internal anatomy of animals that in other sediments which if preserved at all, are only represented by shells, spines, claws, etc. However even such fortuitous circumstances present an incomplete picture of life at the time. The majority of organisms living at the time are probably not represented. This is because the preservation of soft tissues are events restricted to a narrow range of environments.

The events would typically include situations where soft-bodied organisms were preserved very quickly by events such as mudslides. Such rare (abnormal) events which would lead to such a quick burial and preservation make it difficult to study the normal environments of the animals. The sparseness of the fossil record means that organisms are assumed to have existed long before and long after they are found in the fossil record. This is known as the “Signor–Lipps effect”.

Moving on from body fossils, trace fossils consist mainly of tracks and burrows made by extinct organisms. However trace fossils also include coprolites (fossilized feces) and marks left by feeding. Trace fossils are particularly significant because they represent a data source that is not limited to animals with easily fossilized hard parts. They are also significant in that they reflect some aspects of the organisms' behaviors.

Equally significant many trace fossils date substantially earlier than the body fossils of animals that were capable of making the trace fossils. Of course the precise assignment of trace fossils to the organisms that produced them is generally impossible. Nonetheless trace fossils may for example provide the earliest physical evidence of the appearance of moderately complex animals. These would include ancient organisms comparable in structure for example to earthworms.

Geochemical observations may help to deduce the global level of biological activity at a certain period, or the affinity of certain fossils. For example, geochemical features of rocks may reveal when life first arose on Earth. Geochemical features may also provide evidence of the presence of eukaryotic cells, the type from which all multicellular organisms are built. Analyses of carbon isotope ratios may help to explain major transitions such as the Permian–Triassic extinction event.

Naming groups of organisms in a way that is clear and widely agreed is important. Otherwise (believe it or not) some disputes in paleontology have been based merely on misunderstandings over names. Linnaean taxonomy is commonly used for classifying living organisms. However it runs into difficulties when dealing with newly discovered organisms that are significantly different from known ones. For example, it is hard to decide at what level to place a new higher-level grouping, e.g. genus or family or order. This is important since the Linnaean rules for naming groups are tied to their levels. If a group is moved to a different level then it must be renamed.

Paleontologists generally use approaches based on cladistics. Cladistics is a technique for working out the evolutionary "family tree" of a set of organisms. It works by logic. For instance if groups B and C have more similarities to each other than either has to group A, then B and C are more closely related to each other than either is to A. Characteristics that are compared may be anatomical, such as the presence of a notochord. Characteristics may also be molecular, as determined by comparing sequences of DNA or proteins.

The result of a successful analysis is a hierarchy of clades, e.g. groups that share a common ancestor. Ideally the "family tree" has only two branches leading from each node, or "junction". However sometimes there is too little information to achieve this. In those instances paleontologists have to make do with junctions that have several branches. The cladistic technique is sometimes fallible. For example some features such as wings or camera eyes evolved more than once, convergently. This must be taken into account in analyses.

Evolutionary developmental biology, commonly abbreviated to "Evo Devo", also helps paleontologists to produce "family trees" and to better understand fossils. For example the embryological development of some modern brachiopods suggests that brachiopods may be descendants of the halkieriids. Halkieriids became extinct in the Cambrian period.

Paleontology seeks to map out how living things have changed through time. A substantial hurdle to this aim is the difficulty of working out how old fossils are. Beds that preserve fossils typically lack the radioactive elements needed for radiometric dating. This technique is our only means of giving rocks greater than about 50 million years old an absolute age. The technique is particularly valuable as it can be accurate to within 0.5% or better.

Although radiometric dating requires very careful laboratory work, its basic principle is simple. The rates at which various radioactive elements decay are known. So the ratio of the radioactive element to the element into which it decays shows how long ago the radioactive element was incorporated into the rock. Radioactive elements are commonly found only in rocks with a volcanic origin. Thus the only fossil-bearing rocks that can be dated radiometrically are a few volcanic ash layers.

Consequently in the absence of such volcanic ash layers paleontologists are then left to rely on stratigraphy to date fossils. Stratigraphy is the science of deciphering the "layer-cake" that is the sedimentary record. Stratigraphy has often been compared to a jigsaw puzzle. Rocks normally form relatively horizontal layers, with each layer younger than the one underneath it. If a fossil is found between two layers whose ages are known, then obviously the fossil's age must lie between the two known ages.

However rock sequences are not continuous. They may be broken up or made discontinuous by faults or periods of erosion. Consequently it is very difficult to match up rock beds that are not directly next to one another. However fossils of species that survived for a relatively short time can be used to link up isolated rocks or rock layers. This technique is called biostratigraphy.

For instance the conodont Eoplacognathus pseudoplanus has a short range of existence in the Middle Ordovician period. If rocks of unknown age are found to have traces of E. pseudoplanus, they must have a mid-Ordovician age. Such “index fossils” must be distinctive, be globally distributed, and have a short time range to be useful. However misleading results are produced if the index fossils turn out to have longer fossil ranges than first thought.

Stratigraphy and biostratigraphy can in general provide only relative dating (A was before B), which is often sufficient for studying evolution. However this is difficult for some time periods, because of the problems involved in matching up rocks of the same age across different continents. Family-tree relationships may also help to narrow down the date when lineages first appeared.

For instance if fossils of B or C date to X million years ago and the calculated "family tree" says A was an ancestor of B and C, then A must have evolved more than X million years ago. It is also possible to estimate how long ago two living clades diverged – i.e. approximately how long ago their last common ancestor must have lived – by assuming that DNA mutations accumulate at a constant rate.

These "molecular clocks" however are fallible. At best they provide only a very approximate timing. For example they are not sufficiently precise and reliable for estimating when the groups that feature in the Cambrian explosion first evolved. The estimates derived from applying the different techniques may vary by a factor of two.

Earth formed about 4,570 million (4.57 billion) years ago. A collision that formed the Moon occurred about 40 million years later, about 4.53 billion years ago. Earth may thereafter have cooled quickly enough to have oceans and an atmosphere by about 4.44 billion years ago. There is evidence on the Moon of a Late Heavy Bombardment by asteroids from about/between 4 and 3.8 billion years ago. It's likely that this bombardment struck the earth at the same time. If so, the bombardment may have stripped away those first atmosphere and oceans.

Paleontology traces the evolutionary history of life back to over 3 billion years ago, possibly as far as 3.8 billion years ago. The oldest clear evidence of life on Earth dates to 3 billion years ago. However there have been reports (often disputed) of fossil bacteria from 3.4 billion years ago. There is also believed by many to be geochemical evidence for the presence of life 3.8 billion years ago, shortly after the cessation of the asteroid bombardment.

Some scientists have proposed that life on Earth was "seeded" from elsewhere. However but most research concentrates on various explanations of how life could have arisen independently on Earth. For about 2 billion years microbial mats were the dominant life on Earth. There microbial mats were multi-layered colonies of different bacteria. The evolution of oxygenic photosynthesis enabled them to play the major role in the oxygenation of the atmosphere starting about 2.4 billion years ago.

This change in the atmosphere increased their effectiveness as nurseries of evolution. Eukaryotes were cells with complex internal structures. While they may have been present earlier, their evolution speeded up when they acquired the ability to transform oxygen from a poison to a powerful source of metabolic energy. This innovation may have come from primitive eukaryotes capturing oxygen-powered bacteria as endosymbionts and transforming them into organelles called mitochondria.

The earliest evidence of complex eukaryotes with organelles (such as mitochondria) dates from 1.85 billion years ago. Multicellular life is composed only of eukaryotic cells. The earliest evidence for multicellular life is found in the Francevillian Group Fossils from 2.1 billion years ago. However specialization of cells for different functions only first appears between 1.43 million years ago (a possible fungus) and 1.2 billion years ago (a probable red alga).

Sexual reproduction is likely a prerequisite for specialization of cells. Otherwise asexual multicellular organism might be at risk of being taken over by rogue cells that retain the ability to reproduce. The earliest known animals are cnidarians from about 580 million years ago. However these are so modern-looking that they must be descendants of earlier animals yet unknown to science.

Early fossils of animals are rare. This is because they had not developed mineralized, easily fossilized hard parts until about 548 million years ago. The earliest modern-looking bilaterian animals appear in the Early Cambrian. These appeared alongside several "weird wonders" that bear little obvious resemblance to any modern animals.

There is a long-running debate about whether this Cambrian explosion was truly a very rapid period of evolutionary experimentation. Alternative views are that modern-looking animals began evolving earlier, but fossils of their precursors have not yet been found. Another alternate view postulated is that the "weird wonders" are evolutionary "aunts" and "cousins" of modern groups.

Vertebrates remained a minor group until the first jawed fish appeared in the Late Ordovician. Haikouichthys, from about 518 million years ago in China, may be the earliest known fish. The lineage that produced land vertebrates evolved over 100 million years later. The spread of animals and plants from water to land required organisms to solve several problems. These challenges including protection against drying out and supporting themselves against gravity.

The earliest evidence of land plants and land invertebrates date back to about 476 million years ago and 490 million years ago respectively. As indicated by their trace and body fossils those early invertebrates were arthropods known as euthycarcinoids. However they evolved very rapidly between 370 million years ago and 360 million years ago.

Recent discoveries have overturned earlier ideas about the history and driving forces behind their evolution. Land plants were so successful that their detritus caused an ecological crisis in the Late Devonian. This crisis was only resolved by the evolution of fungi that could digest dead wood.

During the Permian period synapsids, including the ancestors of mammals, may have dominated land environments. However this domination ended with the Permian–Triassic extinction event 251 million years ago. The Permian-Triassic extinction event came very close to wiping out all complex life. The extinctions were apparently fairly sudden, at least among vertebrates.

During the slow recovery from this catastrophe a previously obscure group, archosaurs, became the most abundant and diverse terrestrial vertebrates. One archosaur group were the dinosaurs. They became the dominant land vertebrates for the rest of the Mesozoic. Birds evolved from one group of dinosaurs. During this time mammals' ancestors survived only as small, mainly nocturnal insectivores. This niche may have accelerated the development of mammalian traits such as endothermy and hair.

The Cretaceous–Paleogene extinction event 66 million years ago killed off all the dinosaurs except the birds. Birds are the only surviving dinosaurs. After the Cretaceous-Paleogene extinction mammals increased rapidly in size and diversity. Aside from their land-based populations, some took to the air and the sea.

Fossil evidence indicates that in the meanwhile flowering plants had appeared and rapidly diversified in the Early Cretaceous. This occurred during between 130 million years ago and 90 million years ago. The rapid rise of flowering plants to dominance of terrestrial ecosystems is thought to have been propelled by co-evolution with pollinating insects. Social insects had appeared around the same time. Although they account for only small parts of the insect "family tree", social insects now form over 50% of the total mass of all insects.

Humans evolved from a lineage of upright-walking apes. The earliest fossils date from over 6 million years ago. Early members of this lineage had chimp-sized brains, about 25% as big as modern humans'. However there are signs of a steady increase in brain size after about 3 million years ago. There is a long-running debate about whether modern humans are descendants of a single small population in Africa. It is proposed by many researchers that this single population then migrated all over the world less than 200,000 years ago and replaced previous hominine species. The alternate theory is that modern humans arose worldwide roughly at the same time as a result of interbreeding, and originated from a number of populations.

Life on earth has suffered occasional mass extinctions at least since 542 million years ago. Despite their disastrous effects, mass extinctions have sometimes accelerated the evolution of life on earth. When dominance of an ecological niche passes from one group of organisms to another, this is rarely because the new dominant group out-competes the old. Rather it is usually because an extinction event allows a new group to outlive the old and move into its niche.

The fossil record appears to show that the rate of extinction is slowing down. Both the gaps between mass extinctions are becoming longer, and the average and background rates of extinction decreasing. However it is not absolutely certain whether the actual rate of extinction has altered. Both of these observations pertaining to a slowing extinction rate could be explained in several ways.

For instances the oceans may have become more hospitable to life over the last 500 million years. Thus they would be less vulnerable to mass extinctions. Dissolved oxygen has become more widespread and penetrated to greater depths. The development of life on land reduced the run-off of nutrients. This would reduce the risk of eutrophication and anoxic events. Marine ecosystems have also become more diversified so that food chains are less likely to be disrupted.

Reasonably complete fossils are very rare. Most extinct organisms are represented only by partial fossils. Complete fossils are of course rarest in the oldest rocks. So paleontologists have mistakenly assigned parts of the same organism to different genera. This after the genera were created and defined solely to accommodate these finds. The risk of this mistake is higher for older fossils because these are often unlike parts of any living organism. Many "superfluous" genera are represented by fragments that are not found again. These "superfluous" genera are interpreted as having become extinct very quickly.

Biodiversity in the fossil record is "the number of distinct genera alive at any given time; that is, those whose first occurrence predates and whose last occurrence postdates that time". Biodiversity shows shows a different trend than a slowing extinction rate. Biodiversity exhibited a fairly swift rise from 542 to 400 million years ago. Then a slight decline from 400 to 200 million years ago. The devastating Permian–Triassic extinction event was an important factor in that decline. Then after the Permian-Triassic extinction event a swift rise in biodiversity from 200 million years ago to the present.

Although paleontology became established around 1800, earlier thinkers had noticed aspects of the fossil record. The ancient Greek philosopher Xenophanes (570–480 BC) concluded from fossil sea shells that some areas of land were once under water. During the Middle Ages the Persian naturalist Ibn Sina, known as Avicenna in Europe, discussed fossils. Ibn Sina proposed a theory of petrifying fluids on which Albert of Saxony elaborated in the 14th century.

The Chinese naturalist Shen Kuo (1031–1095 AD) proposed a theory of climate change based on the presence of petrified bamboo. The petrified bamboo was found in regions that in his time were too dry for bamboo. In early modern Europe the systematic study of fossils emerged as an integral part of the changes in natural philosophy that occurred during the Age of Reason. In the Italian Renaissance Leonardo da Vinci made various significant contributions to the field as well depicted numerous fossils.

Leonardo's contributions are central to the history of paleontology. Leonardo established a line of continuity between the two main branches of paleontology – ichnology and body fossil paleontology. Ichnofossils were structures left by living organisms. Ichnofossils are significant paleoenvironmental tools as certain ichnofossils show the marine origin of rock strata. Ichnofossils are distinct from body fossils, but can be integrated with body fossils to provide paleontological information. This demonstrates the independence and complementary evidence of ichnofossils and body fossils.

At the end of the 18th century Georges Cuvier's work established comparative anatomy as a scientific discipline. By proving that some fossil animals resembled no living ones he demonstrated that animals could become extinct. This revelation led to the emergence of paleontology. The expanding knowledge of the fossil record also played an increasing role in the development of geology, particularly stratigraphy.

First mention of the word paleontology (“palæontologie”) was in January 1822 by Henri Marie Ducrotay de Blainville in his Journal de physique. He coined the word "palaeontology" to refer to the study of ancient living organisms through fossils. The first half of the 19th century saw geological and paleontological activity become increasingly well organized. This period witnessed the growth of geologic societies and museums. As well there was an increasing number of professional geologists and fossil specialists.

Interest increased for reasons that were not purely scientific. For instance geology and paleontology helped industrialists to find and exploit natural resources such as coal. This contributed to a rapid increase in knowledge about the history of life on Earth. This also led to progress in defining the geologic time scale, which was largely based on fossil evidence. As knowledge of life's history continued to improve, it became increasingly obvious that there had been some kind of successive order to the development of life. This encouraged early evolutionary theories on the transmutation of species.

After Charles Darwin published Origin of Species in 1859 much of the focus of paleontology shifted to understanding evolutionary paths. These pathways included human evolution and evolutionary theory. The last half of the 19th century saw a tremendous expansion in paleontological activity. This was especially evident in North America. The trend continued in the 20th century with additional regions of the Earth being opened to systematic fossil collection.

Fossils found in China near the end of the 20th century have been particularly important. They have provided new information about the earliest evolution of animals, early fish, dinosaurs and the evolution of birds. The last few decades of the 20th century has also witnessed a strongly renewed interest in mass extinctions and their role in the evolution of life on Earth. There has also been a renewed interest in the Cambrian Explosion that apparently saw the development of the body plans of most animal phyla. The discovery of fossils of the Ediacaran biota and developments in paleobiology extended knowledge about the history of life back far before the Cambrian.

Increasing awareness of Gregor Mendel's pioneering work in genetics led first to the development of population genetics and then in the mid-20th century to the modern evolutionary synthesis. This explains evolution as the outcome of events such as mutations and horizontal gene transfer. These events provide genetic variation, with genetic drift and natural selection driving changes in this variation over time. Within the next few years the role and operation of DNA in genetic inheritance were discovered. This led to what is now known as the "Central Dogma" of molecular biology.

In the 1960's molecular phylogenetics began to make an impact. Molecular phylogenetics involves the investigation of evolutionary "family trees" by techniques derived from biochemistry. The impact of molecular phylogenetics has been particularly significant in suggesting that the human lineage had diverged from apes much more recently than was generally assumed. Although this early study compared proteins from apes and humans, most molecular phylogenetics research is now based on comparisons of RNA and DNA.

Paleobiology:Paleobiology is a growing and comparatively new discipline which combines the methods and findings of the life science biology with the methods and findings of earth science paleontology. It is occasionally referred to as geobiology. Paleobiological research uses biological field research of current biota and of fossils millions of years old to answer questions about the molecular evolution and the evolutionary history of life. In this scientific quest, macrofossils, microfossils and trace fossils are typically analyzed. In addition however 21st century biochemical analysis of DNA and RNA samples offers much promise, as does the biometric construction of phylogenetic trees.

Related sub-specialties include:

Paleobotany, which applies the principles and methods of paleobiology to flora, especially green land plants. However paleobotany also includes the fungi and seaweeds (algae). Paleobotany also involves mycology, phycology and dendrochronology.

Paleozoology uses the methods and principles of paleobiology to understand fauna, both vertebrates and invertebrates. Paleozoology also involves vertebrate and invertebrate paleontology, as well as applies paleobiologic principles and methods to archaea, bacteria, protists and microscopic pollen/spores. It also involves the study of microfossils and palynology.

Paleovirology examines the evolutionary history of viruses on paleobiological timescales.

Paleobiochemistry uses the methods and principles of organic chemistry to detect and analyze molecular-level evidence of ancient life, both microscopic and macroscopic.

Paleoecology examines past ecosystems, climates, and geographies so as to better comprehend prehistoric life.

Taphonomy analyzes the post-mortem history of individual organisms. This history would, for example, include decay and decomposition. Researchers thus gain insights into the behavior, death and environment of the fossilized organisms.

Paleoichnology analyzes the tracks, borings, trails, burrows, impressions, and other trace fossils left by ancient organisms. This allows researchers to gain insights into the behavior and ecology of the ancient organisms.

Stratigraphic paleobiology studies long-term secular changes as well as the (short-term) bed-by-bed sequence of changes in the characteristics and behaviors or ancient organisms. This sub-discipline is closed related to studies of stratification, sedimentary rocks, and the geologic time scale.

Evolutionary developmental paleobiology examines the evolutionary aspects of the modes and trajectories of growth and development in the evolution of life. This includes organisms both extinct and extant. The sub-discipline is closed related to studies of adaptive radiation, cladistics, evolutionary biology, developmental biology and phylogenetic trees.

The founder or "father" of modern paleobiology was Baron Franz Nopcsa who lived from 1877 to 1933). Nopcsa was a Hungarian scientist trained at the University of Vienna. He initially termed the discipline "paleophysiology." Credit for coining the word paleobiology itself goes to Professor Charles Schuchert. He proposed the term in 1904. His stated intent was to initiate "a broad new science" joining "traditional paleontology with the evidence and insights of geology and isotopic chemistry."

Charles Doolittle Walcott has been cited as the "founder of Precambrian paleobiology." Walcott was a Smithsonian adventurer. Walcott is best known to history as the discoverer of the mid-Cambrian Burgess shale animal fossils. In 1883 this American curator found the "first Precambrian fossil cells known to science". This was in the form of a stromatolite reef then known as Cryptozoon algae. In 1899 Walcott discovered the first acritarch fossil cells. These were a Precambrian algal phytoplankton he named “Chuaria”. And finally in 1914 Walcott reported "minute cells and chains of cell-like bodies" belonging to Precambrian purple bacteria.

Later 20th century paleobiologists have also figured prominently in finding Archaean and Proterozoic eon microfossils. In 1954 Stanley A. Tyler and Elso S. Barghoorn described 2.1 billion-year-old cyanobacteria and fungi-like microflora at their Gunflint Chert fossil site. Eleven years later in 1965 Barghoorn and J. William Schopf reported finely-preserved Precambrian microflora at their Bitter Springs site of the Amadeus Basin, Central Australia. Then in 1993 Schopf discovered O2-producing blue-green bacteria at his 3.5 billion-year-old Apex Chert site in Pilbara Craton, Marble Bar, in the northwestern part of Western Australia. So paleobiologists were at last homing in on the origins of the Precambrian "Oxygen catastrophe."

Paleoclimatology: Paleoclimatology is the study of climates for which direct measurements were not taken. As instrumental records only span a tiny part of Earth's history, the reconstruction of ancient climate is important. This enables researchers to better understand natural variation and the evolution of the current climate. Paleoclimatology uses a variety of proxy methods from Earth and life sciences to obtain data previously preserved within rocks, sediments, boreholes, ice sheets, tree rings, corals, shells, and microfossils. Combined with techniques to date the proxies, these paleoclimatological records are used to determine the past states of Earth's atmosphere.

The scientific field of paleoclimatology came to maturity in the 20th century. Notable periods studied by paleoclimatologists are many. These include the frequent glaciations Earth has undergone. Also the rapid cooling events such as the Younger Dryas. And as well the fast rate of warming during the Paleocene–Eocene Thermal Maximum. Studies of past changes in the environment and biodiversity often reflect on the current situation. This to specifically include the impact of climate on mass extinctions and biotic recovery, as well as how this might affect the current period of global warming.

Notions of a changing climate probably evolved in ancient Egypt, Mesopotamia, the Indus Valley and China. There prolonged periods of droughts and floods were experienced. In the 17th century Robert Hooke postulated that fossils of giant turtles found in Dorset could only be explained by a once warmer climate. He attributed the warmer climate as the result of a shift in Earth's axis. Keep in mind that at that point in tome fossils were often explained as a consequence of a Biblical flood. It was not until the 19th century that systematic observations of sunspots started by amateur astronomer initiated a discussion pertaining to the Sun's influence on Earth's climate.

Still early in the 19th century the scientific study of paleoclimatology began to further take shape. This occurred when discoveries about glaciations and natural changes in Earth's past climate helped explain and understand the greenhouse effect. But it was only in the 20th century that paleoclimatology became a unified scientific field. Before then different aspects of Earth's climate history were studied by a variety of disciplines.

By the end of the 20th century the empirical research into Earth's ancient climates started to be combined with computer models of increasing complexity. A new objective also developed in this period. That was finding ancient analog climates that could provide information about current climate change. Today paleoclimatologists employ a wide variety of techniques to deduce ancient climates.

The techniques employed are dependent on what variables have to be reconstructed. These might include for instance temperature, precipitation, or some other aspect of past climates. These techniques are also variable based on how long ago the climate of interest occurred. For instance the deep marine record is the source of most isotopic data. However this record exists only on oceanic plates. These records disappear when the oceanic plates are eventually subducted. The oldest remaining material is 200 million years old. Additionally older sediments are also more prone to corruption by diagenesis. Resolution and confidence in the data decrease over time. Mountain glaciers and the polar ice caps/ice sheets provide much data in paleoclimatology. Ice-coring projects in the ice caps of Greenland and Antarctica have yielded data going back several hundred thousand years. In the case of the EPICA project the sample cores actually dated over 800,000 years ago.

Air trapped within fallen snow becomes encased in tiny bubbles. Then the snow is compressed into ice in the glacier under the weight of later years' snow. The trapped air has proven a tremendously valuable source for direct measurement of the composition of air from the time the ice was formed. Layering can be observed because of seasonal pauses in ice accumulation. The naturally occurring layering can be used to establish chronology, associating specific depths of the core with ranges of time. Changes in the layering thickness can also be used to determine changes in precipitation or temperature.

The varying amount of oxygen-18 isotope found in ice layers represent changes in average ocean surface temperature. Water molecules containing the heavier O-18 evaporate at a higher temperature than water molecules containing the normal Oxygen-16 isotope. The ratio of O-18 to O-16 will be higher as temperature increases. The ratio of O-18 to O-16 is also influenced by other factors such as the water's salinity and the volume of water locked up in ice sheets. Various historical cycles in those isotope ratios have been recorded.

Pollen has been observed in ice cores and has been used to understand which plants were present as the layer formed. Pollen is produced in abundance and its distribution is typically well understood. A pollen count for a specific layer can be determined by observing the total amount of pollen categorized by type in a controlled sample of that layer. Changes in plant frequency over time can be plotted through statistical analysis of pollen counts in the core.

Knowing which plants were present leads to an understanding of precipitation and temperature, and types of fauna present. Palynology includes the study of pollen for these purposes. In addition volcanic ash is contained in some layers. The ash can be used to establish the time of the formation of the layer of ice. Each volcanic event distributes ash with a unique set of properties. These properties include the shape and color of particles, as well as the chemical signature of the ice. Establishing the ash's source will establish a range of time to associate with layer of ice.

A multinational consortium drilled an ice core in Dome C on the East Antarctic ice sheet. The consortium is known as the European Project for Ice Coring in Antarctica (EPICA). EPICA was able to retrieve ice core samples from layers created roughly 800,000 years ago. The international ice core community has defined a priority project to obtain the oldest possible ice core record from Antarctica. Under the auspices of International Partnerships in Ice Core Sciences (IPICS) an effort will be made to retrieve an ice core record reaching back to 1.5 million years ago.

Climatic information can be obtained through an understanding of changes in tree growth. Generally trees respond to changes in climatic variables by speeding up or slowing down growth. This growth pattern is in turn generally reflected by a greater or lesser thickness in growth rings. A tree-ring record is established by compiling information from many living trees in a specific area. It is important to note however that different species respond to changes in climatic variables in different ways.

Some older intact wood samples fortuitously escape decay can. These intact samples can extend the time covered by the dendrotic record. This is achieved by matching the ring depth changes to contemporary specimens. By using that method some areas have tree-ring records dating back a few thousand years. Older wood not connected to a contemporary record can be dated generally with radiocarbon techniques. A tree-ring record can be used to produce information regarding precipitation, temperature, hydrology, and fire corresponding to a particular area.

In working with longer time scales geologists must refer to the sedimentary record for data. Sediments are sometimes lithified to form rock. These sedimentary rocks may contain remnants of preserved vegetation, animals, plankton, or pollen. These preserved organic remains may help establish the characteristics of certain climatic zones. Biomarker molecules such as the alkenones may yield information about their temperature of formation. Chemical signatures as well can be used to reconstruct past temperature. This is particularly so of the Mg/Ca ratio of calcite in Foraminifera tests.

Isotopic ratios can provide further information. Specifically the O-18 isotope record responds to changes in temperature and ice volume. The O-13 isotope record reflects a wide range of factors which are often more difficult to disentangle, identify, and quantify. Sedimentary sea floor core sample are labeled to identify the exact spot on the sea floor where the sample was taken. Sediments from nearby locations can show significant differences in chemical and biological composition.

On a longer time scale, the rock record may show signs of sea level rise and fall. Oftentimes features such as "fossilized" sand dunes can be identified. Scientists can get a grasp of long term climate by studying sedimentary rock going back billions of years. The division of earth history into separate periods is largely based on visible changes in sedimentary rock layers that demarcate major changes in conditions. Often they include major shifts in climate.

The study of fossilized coral is known as “sclerochronology”. Coral "rings" are similar to tree rings except that they respond to a wider variety of ecological stimuli. These influences include water temperature, freshwater influx, pH changes, and wave action. From those “records” specialized equipment can be used to deduce the sea surface temperature and water salinity from the past few centuries. The O-18 isotope range of coralline red algae provides a useful proxy of the combined sea surface temperature and sea surface salinity at high latitudes and the tropics, where many traditional techniques are limited.

Within climatic geomorphology one approach often utilized by the discipline's researchers is to study relict landforms and thereby infer ancient climates. The study of past climates climatic geomorphology is considered by some researchers to be a theme of historical geology. However climatic geomorphology is of limited use to study recent (Quaternary, Holocene) large climate changes. This is due to the fact that these are seldom discernible in the geomorphological record.

The field of geochronology has scientists working on determining how old certain proxies are. For recent proxy archives of tree rings and corals the individual year rings can be counted and an exact year can be determined. Radiometric dating uses the properties of radioactive elements in proxies. In older material more of the radioactive material will have decayed. Thus the proportion of different elements will be different when contrasted with newer proxies.

One example of radiometric dating is radiocarbon dating. In the air cosmic rays constantly convert nitrogen into a specific radioactive carbon isotope known as “14C”. Plants then use this carbon to grow. However this isotope is not replenished anymore when the plant ties, and the 14C starts decaying. The proportion of 'normal' carbon and Carbon-14 gives information of how long the plant material has not been in contact with the atmosphere.

Knowledge of precise climatic events decreases as the record goes back in time, but some notable climate events are known. The first notable climactic event of course is at earth's beginning, and is known as the “Faint Young Sun Paradox”. Following is the “Huronian Glaciation” of about 2.4 billion years ago. At the point in time Earth was completely covered in ice, probably due to the “Great Oxygenation Event”. The “Later Neoproterozoic Snowball Earth” of about 600 million years ago was the precursor to the “Cambrian Explosion”.

Following was the “Andean-Saharan Glaciation” of about 450 million years ago. Following that was the “Carboniferous Rainforest Collapse” of about 300 million years ago. The the Earth's climate was rocked by the “Permian–Triassic Extinction Event of 251.4 million years ago. Thereafter followed a number of “Oceanic Anoxic Events”, notably those of about 120 and 93 million years ago, and later followed by other such events.

This was followed by yet another trauma to Earth known as the “Cretaceous–Paleogene Extinction Event of about 66 million years ago. This was followed by what is known as the “Paleocene–Eocene Thermal Maximum” of 55 million years ago. Then by the most recent “ice age” known as the “Younger Dryas” or “The Big Freeze” or about 11,000 BC. As the ice age receded Earth basked in the “Holocene climatic optimum” of about 7,000 through 3,000 BC. There were extreme weather events of 535-536 AD. This was followed by the “Medieval Warm Period” between about 900 and 1300 AD. This was followed by the “Little Ice Age” of 1300 to 1800 AD. And finally the most notable climatic event of the recent past, the “Year Without a Summer” of 1816.

Moving on the the study of Earth's past atmospheres, the first atmosphere would have consisted of gases in the solar nebula, primarily hydrogen. In addition, there would probably have been simple hydrides such as those now found in gas giants like Jupiter and Saturn. These would have principally consisted of water vapor, methane, and ammonia. As the solar nebula dissipated these gases would have escaped the atmosphere, in part driven off by the solar wind.

Earth's next atmosphere would have consisted largely of nitrogen, carbon dioxide, and inert gases. The atmosphere was produced by outgassing from volcanism. The gasses produced by volcanism would have been supplemented supplemented the by gases produced during the late heavy bombardment of Earth by huge asteroids. A major part of carbon dioxide emissions produced to have been rapidly dissolved in water and built up as carbonate sediments.

Such water-related sediments have been found dating from as early as 3.8 billion years ago. About 3.4 billion years ago nitrogen was the major part of the then stable "second atmosphere". An influence of life has to be taken into account rather soon in the history of the atmosphere because hints of early life forms have been dated to as early as 3.5 billion years ago. The fact that it is not perfectly in line with the early sun's 30% lower solar radiance (compared to today) of the has been described as the "Faint Young Sun Paradox".

The geological record shows a continually and relatively warm surface during the complete early temperature record of Earth. The only significant exception was a cold glacial phase about 2.4 billion years ago. In the late Archaean eon an oxygen-containing atmosphere began to develop. The apparent cause was photosynthesizing cyanobacteria which have been found as stromatolite fossils from 2.7 billion years ago. Scientists refer to this as “the Great Oxygenation Event'.

The early basic carbon isotopy (isotope ratio proportions) was very much in line with what is found today. This fact suggests that the fundamental features of the carbon cycle were established as early as 4 billion years ago. The constant rearrangement of continents by plate tectonics influences the long-term evolution of the atmosphere. This process transfers carbon dioxide to and from large continental carbonate stores.

Free oxygen did not exist in the atmosphere until about 2.4 billion years ago, this during the Great Oxygenation Event. The appearance of free atmospheric oxygen is indicated by the end of the banded iron formations. Until then any oxygen produced by photosynthesis was consumed by oxidation of reduced materials, notably iron. Molecules of free oxygen did not start to accumulate in the atmosphere until the rate of production of oxygen began to exceed the availability of reducing materials.

At that point there was a shift from a reducing atmosphere to an oxidizing atmosphere. Atmospheric oxygen levels showed major variations until reaching a steady state of more than 15% by the end of the Precambrian. The succeeding time span was the Phanerozoic eon. It was at this point in the history of life that oxygen-breathing metazoan life forms began to appear. The amount of oxygen in the atmosphere has fluctuated over the last 600 million years. It reached a peak of 35% during the Carboniferous period. That was significantly higher than today's 21%.

Two main processes govern changes in the atmosphere. The first is the fact that plants use carbon dioxide from the atmosphere and in turn release oxygen back into the atmosphere. The second process involves the breakdown of pyrite and volcanic eruptions which release sulfur into the atmosphere. This oxidizes and that reduces the amount of oxygen in the atmosphere. However volcanic eruptions also release carbon dioxide, which plants can convert to oxygen.

The precise causes of the historical variations of the amount of oxygen in the atmosphere is not known. Periods with much oxygen in the atmosphere are associated with rapid development of animals. Today's atmosphere contains 21% oxygen. This is high enough for rapid development of animals.

Amongst the most profound influences in the history of earth have been the various glacial events. The Huronian glaciation is the first known glaciation in Earth's history. It lasted from about 2.4 to 2.1 billion years ago, The Cryogenian glaciation lasted from 720 to 635 million years ago. The Andean-Saharan glaciation lasted from 450 to 420 million years ago. The Karoo glaciation lasted from 360 to 260 million years ago.

We're presently in the Quaternary glaciation. It is the current glaciation period and began 2.58 million years ago. In 2020 scientists published a continuous, high-fidelity record of variations in Earth's climate during the past 66 million years. The study identified four climate states, separated by transitions that include changing greenhouse gas levels and polar ice sheets volumes. They integrated the data of various sources. The warmest climate state since the time of the dinosaur extinction is known as the "Hothouse". It lasted from about 56 to 47 million years ago. The mean average temperature on the plant was 25 degrees warmer than today (14C).

The climate of the late Precambrian showed some major glaciation events spreading over much of the earth. At this time the continents were bunched up in the Rodinia supercontinent. Massive deposits of tillites and anomalous isotopic signatures are found. The presence of these deposits gave rise to the Snowball Earth hypothesis. As the Proterozoic Eon drew to a close the Earth started to warm up.

By the dawn of the Cambrian and the Phanerozoic life forms were abundant and gave rise to what is known as “the Cambrian explosion”. At that point in time the average global temperatures were around 72 (22C). The Phanerozoic climate refers to the most recent 500 million years which has witnessed variances in the oxygen (18) isotope ratios, indicating climate change events.

Major drivers for the preindustrial ages have been variations of the sun, volcanic ashes and exhalations, relative movements of the earth towards the sun, and tectonically induced effects as for major sea currents, watersheds, and ocean oscillations. In the early Phanerozoic increased atmospheric carbon dioxide concentrations have been linked to driving or amplifying increased global temperatures. Research has determined a climate sensitivity for the latter Phanerozoic which was calculated to be similar to today's modern range of values.

The difference in global mean temperatures between a fully glacial Earth and an ice free Earth is estimated at approximately 18 degrees farenheit (10 degrees centigrade). Of course far larger changes would have been observed at higher latitudes, and smaller ones at low latitudes. One requirement for the development of large scale ice sheets seems to be the arrangement of continental land masses at or near the poles. The constant rearrangement of continents by plate tectonics can also shape long-term climate evolution.

However the presence or absence of land masses at the poles is not sufficient to guarantee glaciations or exclude polar ice caps. Evidence exists of past warm periods in Earth's climate when polar land masses similar to Antarctica were home to deciduous forests rather than ice sheets. The relatively warm local minimum between the Jurassic and Cretaceous goes along with an increase of subduction and mid-ocean ridge volcanism. These were due to the breakup of the Pangea supercontinent.

Superimposed on the long-term evolution between hot and cold climates have been many short-term fluctuations in climate. These have been both similar to and sometimes more severe than the varying glacial and interglacial states of the present ice age. Some of the most severe fluctuations may be related to rapid climate changes due to sudden collapses of natural methane clathrate reservoirs in the oceans.

One such example was the “Paleocene-Eocene Thermal Maximum”. A similar, single event of induced severe climate change after a meteorite impact has been proposed as reason for the Cretaceous–Paleogene extinction event. Other major thresholds are the Permian-Triassic and Ordovician-Silurian extinction events with various reasons suggested.

Ice core data for the past 800,000 years has enabled great insights into the Quaternary climate. The Quaternary geological period includes the current climate. There has been a cycle of ice ages for the past 2.2–2.1 million years. These actually started before the Quaternary, in the late Neogene Period. The data reveal cycles of about 120,000 years. It has been observed that ice ages deepen by progressive steps, but the recovery to interglacial conditions occurs in one big step.

Climate forcing is the difference between radiant energy (sunlight) received by the Earth and the outgoing longwave radiation back to space. Radiative forcing is quantified based on the CO2 amount in the tropopause. Dependent on the radiative balance of incoming and outgoing energy, the Earth either warms up or cools down. Earth radiative balance originates from changes in solar insolation and the concentrations of greenhouse gases and aerosols. Climate change may be due to internal processes in Earth sphere's and/or following external forcings.

The Earth's climate system involves the atmosphere, biosphere, cryosphere, hydrosphere, and lithosphere. The sum of these processes from Earth's spheres is what affects the climate. Greenhouse gasses act as the internal forcing of the climate system. Particular interests in climate science and paleoclimatology focus on the study of earth climate sensitivity in response to the sum of forcings.

External forcings include the Milankovitch cycles which determine both the distance between earth and the sun as well as the orientation of earth to the sun. Forcings also include solar insolation, which is the total amount of solar radiation received by Earth. Volcanic eruptions are also considered an external forcing. They also include human changes influencing the composition of the atmosphere as well as influences pertaining to land use.

On timescales of millions of years the uplift of mountain ranges and subsequent weathering processes of rocks and soils are an important part of the carbon cycle. This includes as well the subduction of tectonic plates. The weathering sequesters CO2 include the reaction of minerals with chemicals, especially silicate weathering with CO2. This removes CO2 from the atmosphere and reduces the radiative forcing. The opposite effect is volcanism. Volcanism is be responsible for a natural greenhouse effect by emitting CO2 into the atmosphere. This affects glaciation (Ice Age) cycles.

Scientists suggest that humans emit CO2 10,000 times faster than natural processes have done in the past. Other players include ice sheet dynamics and continental positions, as well as consequential vegetation changes. All of these have been and continue to be important factors in the long term evolution of the earth's climate. There is also a close correlation between CO2 and temperature, where CO2 levels have a strong control over global temperatures in Earth history. Paleoclimatology: Historical geology or paleogeology is a discipline that uses the principles and techniques of geology to reconstruct and understand the geological history of Earth. It focuses on geologic processes that change the Earth's surface and subsurface. It employs stratigraphy, structural geology and paleontology to determine the sequence of these events. Paleogeology also focuses on the evolution of plants and animals during different time periods in the geological timescale.

The discovery of radioactivity and the development of several radiometric dating techniques in the first half of the 20th century provided a means of deriving absolute versus relative ages of geologic history. A sub-specialty known as “economic geology” is involves the search for and extraction of fuel and raw materials. Economic geology is heavily dependent on an understanding of the geological history of an area. Another sub-specialty is environmental geology. Its focus includes most significantly the study of the geologic hazards of earthquakes and volcanism. This sub-specialty as well is heavily dependent on detailed knowledge of geologic history.

Nicolaus Steno was the first to observe and propose some of the basic concepts of historical geology. Also known as as Niels Stensen he is considered to be the "father of geology". One of his (then) controversial and revolutionary concepts was that fossils originally came from living organisms. His other equally famous observations are often grouped together to form the laws of stratigraphy.

James Hutton and Charles Lyell also contributed to early understanding of the Earth's history. Their contributions included observations at Edinburgh in Scotland concerning angular unconformity in a rock face. In fact it was Lyell that influenced Charles Darwin greatly in his theory of evolution. Lyell influences included his belief (then speculative) that the present is the key to the past.

Hutton first proposed the theory of “uniformitarianism”. This is now a basic principle in all branches of geology. Hutton also supported the idea that the Earth was very old. This was in opposition to the prevailing concept of the time. The prevailing view was that the Earth had only been around a few millennia. Uniformitarianism describes an Earth which was created by the same natural phenomena remain at work today.

The prevailing concept of the 18th century in the West was that earth was very young, and its history had been dominated by catastrophic events. This view was strongly supported by adherents of Abrahamic religions. This belief was based largely on a literal interpretation of their religious scriptural passages. The concept of uniformitarianism met with considerable resistance and the catastrophism vs. gradualism debate of the 19th century resulted.

A variety of discoveries in the 20th century provided ample evidence that Earth history is a product of both gradual incremental processes and sudden cataclysmic events. Violent events such as meteorite impacts and large volcanic explosions do shape the Earth's surface. However this is in addition to gradual processes throughout earth's history such as weathering, erosion and deposition. The present is the key to the past, and it includes catastrophic as well as gradual processes.

SHIPPING & RETURNS/REFUNDS: We always ship books domestically (within the USA) via USPS INSURED media mail (“book rate”). Most international orders cost an additional $19.99 to $53.99 for an insured shipment in a heavily padded mailer. There is also a discount program which can cut postage costs by 50% to 75% if you’re buying about half-a-dozen books or more (5 kilos+). Our postage charges are as reasonable as USPS rates allow. ADDITIONAL PURCHASES do receive a VERY LARGE discount, typically about $5 per book (for each additional book after the first) so as to reward you for the economies of combined shipping/insurance costs.

Your purchase will ordinarily be shipped within 48 hours of payment. We package as well as anyone in the business, with lots of protective padding and containers. All of our shipments are fully insured against loss, and our shipping rates include the cost of this coverage (through stamps.com, Shipsaver.com, the USPS, UPS, or Fed-Ex). International tracking is provided free by the USPS for certain countries, other countries are at additional cost.

We do offer U.S. Postal Service Priority Mail, Registered Mail, and Express Mail for both international and domestic shipments, as well United Parcel Service (UPS) and Federal Express (Fed-Ex). Please ask for a rate quotation. Please note for international purchasers we will do everything we can to minimize your liability for VAT and/or duties. But we cannot assume any responsibility or liability for whatever taxes or duties may be levied on your purchase by the country of your residence. If you don’t like the tax and duty schemes your government imposes, please complain to them. We have no ability to influence or moderate your country’s tax/duty schemes.

If upon receipt of the item you are disappointed for any reason whatever, I offer a no questions asked 30-day return policy. Send it back, I will give you a complete refund of the purchase price; 1) less our original shipping/insurance costs, 2) less any non-refundable fees imposed by Please note that though they generally do, may not always refund payment processing fees on returns beyond a 30-day purchase window. So except for shipping costs and any payment processing fees not refunded by , we will refund all proceeds from the sale of a return item. Obviously we have no ability to influence, modify or waive policies.

ABOUT US: Prior to our retirement we used to travel to Eastern Europe and Central Asia several times a year seeking antique gemstones and jewelry from the globe’s most prolific gemstone producing and cutting centers. Most of the items we offer came from acquisitions we made in Eastern Europe, India, and from the Levant (Eastern Mediterranean/Near East) during these years from various institutions and dealers. Much of what we generate on Etsy, Amazon and goes to support worthy institutions in Europe and Asia connected with Anthropology and Archaeology. Though we have a collection of ancient coins numbering in the tens of thousands, our primary interests are ancient/antique jewelry and gemstones, a reflection of our academic backgrounds.

Though perhaps difficult to find in the USA, in Eastern Europe and Central Asia antique gemstones are commonly dismounted from old, broken settings – the gold reused – the gemstones recut and reset. Before these gorgeous antique gemstones are recut, we try to acquire the best of them in their original, antique, hand-finished state – most of them originally crafted a century or more ago. We believe that the work created by these long-gone master artisans is worth protecting and preserving rather than destroying this heritage of antique gemstones by recutting the original work out of existence. That by preserving their work, in a sense, we are preserving their lives and the legacy they left for modern times. Far better to appreciate their craft than to destroy it with modern cutting.

Not everyone agrees – fully 95% or more of the antique gemstones which come into these marketplaces are recut, and the heritage of the past lost. But if you agree with us that the past is worth protecting, and that past lives and the produce of those lives still matters today, consider buying an antique, hand cut, natural gemstone rather than one of the mass-produced machine cut (often synthetic or “lab produced”) gemstones which dominate the market today. We can set most any antique gemstone you purchase from us in your choice of styles and metals ranging from rings to pendants to earrings and bracelets; in sterling silver, 14kt solid gold, and 14kt gold fill. When you purchase from us, you can count on quick shipping and careful, secure packaging. We would be happy to provide you with a certificate/guarantee of authenticity for any item you purchase from us. There is a $3 fee for mailing under separate cover. I will always respond to every inquiry whether via email or message, so please feel free to write.

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