Over at Uncommon Descent:

It seems that every day there some new news item from science detailing how scientists in search of an optimal solution to their problem at hand, end up finding their solution in biological nature. This latest from PhysOrg.com shows how, in the nano-world, engineering solutions abound. Is it a marvel of natural selection?

Here you?ll find one instance of what I think, taken together, poses a challenge to Darwinian orthodoxy that it can?t meet.


Article:

What these three natural materials have in common, scientists Paul Hansma, Patricia Turner and Rodney Ruoff found, is an optimized adhesive based on sacrificial bonds and the hidden length mechanism. The scientists foresee that these characteristics may help researchers design and fabricate optimized adhesives for nanocomposite materials, such as carbon nanotubes and graphene sheets.

?It?s important to make a composite material without compromising the material?s properties of the strong components, such as the nanotube or graphene sheet,? Hansma explained to PhysOrg.com. Optimal glue would enable these materials to retain their intrinsic properties?especially strength.

As Hansma et al. explain in their paper in Nanotechnology, optimized adhesives can hold together strong elements of materials, and yield just before these elements would break, so as not to cause the entire structure to break.

To achieve this precise strength and damage resistance, biomaterials make use of sacrificial bonds. These weak bonds form from charged side groups on biological adhesive molecules (such as polymers). With the addition of energy due to the stretching of the material, these weak bonds break?however, the process is reversible, giving the material the ability to heal itself. Human and animals bones, abalone shells, and spider silk all make use of this mechanism of sacrificial bonds and hidden length.

?Abalone shell and bone can heal themselves due to the weak bonds, such as hydrogen bonds or ionic bonds, that can reform,? Hansma explained.

The key to obtaining a perfect amount of adhesive force is to use a precise amount of adhesive itself. Hansma et al. explain that nature acts frugally, with glue often making up as little as one percent of the entire material, by weight. Sometimes, nature even prefers voids over extra glue?which contrasts with current engineering, note the scientists, where the space between elements is often completely filled in with epoxy.

As the scientists explain, the longer the material (such as a steel bar) the lower the percentage of adhesive weight. They point out that one type of material??ultra-high-molecular-weight polyethylene chains??is so long that the weak interactions between the chains themselves provide enough adhesion for the structure, and no added glue is needed at all.

?Nature's adhesives tend to be charged polymers, long polypeptides with both positive and negative charged groups along the backbone,? said Hansma. ?These adhesives tend to use water as an environment in which weak bonds involving those charged groups can form, break and reform. The challenge will be to simulate these reformable bonds in man-made adhesives.?



What are people's thoughts?


Blacknad

The implicit argument that PaV puts forth in that article is the same one that PaV put forth. They have a very strong tendency to "pub-jack" ; that is, to take a legitimate scientific work and then "reinterpret it", usually by making assertions that were not made in the original article or by altering the assertion in key ways, and by making inferences that are obviously incorrect.

Blacknad wrote:
"... poses a challenge to Darwinian orthodoxy that it can?t meet."

I don't see anything here that challenges evolution in even the smallest way. Can you be more explicit in what is of concern?

I don't think they are saying it challenges evolution. As far as I know, they accept evolution but think it has been given direction. As they say, they think these seemingly engineered materials challenge Darwinian orthodoxy.

They don't accept that such incredibly finely balanced complexity can arise naturally. I think this is an argument from incredulity.

Blacknad.

Their acceptance is not required.

Again they are assuming the end-product, as we view it on January 12 of 2006 is a designed end-point. They assume it is the only solution, that it is an optimal solution, that at some point in time it did not exist and then later it existed without any intermediary solutions.

Far more reasonable would be to assume that cells are complex entities containing a wide variety of chemical species. And that as they interact with their environment they occasionally, but rarely, form new components. Some of these new arrangements are fatal, the creature dies, and it is not passed on. Others are superior and enable to creature to survive better than its compatriots.

Consider sickle cell anemia. It is both harmful and useful. Depends on the circumstances. We tend to look at reproduction through a microscope that is highly selective. A more realistic appraisal would be that the vast majority of attempts to reproduce end in failure. Ever consider why? It isn't luck.

They do make that point about seeming sudden appearance and disappearance:

"Fun facts you should know.

For every 1000 species that has ever lived during the history of our planet, 999 of them became extinct in an evolutionary dead end street (no species descended from them). Estimates range up to 5 billion species that have walked, crawled, swam, flew, rooted, or slimed our planet in the past. About 10 million are alive today and we have names for about 1 million of those. The average lifespan of a species is about 10 million years. Most species enter the fossil record abruptly and disappear abruptly looking mostly the same at both entrance and exit. The next time you?re thinking of how random mutation and natural selection works keep in mind that in the vast majority of cases it keeps a species looking pretty much the same for about 10 million years then kills it without leaving any descendents."

Blacknad.

Then we come to the question: What is a species?

*sigh* Here we go again.

Your a biologist Rose ... stop sighing and weigh in with an opinion. ;-)

My argument would be that not all these species have technically become extinct. They merely evolved into something else.

HOw about another round of living fossils?

http://www.eurekalert.org/pub_releases/2002-04/m-mds041702.php

Description of a new order, and several species therefrom, with pictures of living and preserved specimens.

I don't want to jump on the species band wagon. There are lumpers and splitters, but mainly it's about reproduction. If they can cross and produce fertile offspring, lumpers would say they're one species. If they can cross but the offspring is infertile, splitters would say they are two separate species. There's the whole rye-wheat-triticale business, too. Plants can do amazing things like diploid or even triploid chromosomes.

For arguments about species I'll stick to bacteriology where my expertise lies. An E. coli is an E. coli, and that's that. You've got a single circular chromosome, a few plasmids for variety, cut and dried. NOthing like these eukaryotes and their fancy chromosomes and pairing for mitosis or meiosis. It's all microtubules and chromosome pairing in eukaryotes. What's really amazing is how often it can go right.

DA wrote:

You're a biologist Rose ... stop sighing and weigh in with an opinion.

Yes Rose. Which of the approximately 30 definitions do you accept? For example here is a short (ha ha) discussion on the subject. Anyone who can get right through it deserves a medal. And the last section is called "Does the species category exist?":

http://plato.stanford.edu/entries/species/

Sorry Rose. For some reason your post didn't show up till after I'd put mine on. You say splitters separate species by whether they form fertile hybrids or not. Not true. Many splitters regard groups that can certainly form fertile hybrids as being separate species. I'd remind you of the ducks I mentioned some time back on another thread. Of course if the idea of a somehow separate species is used to protect some natural region I'm largely in favour. Still if NZ was discovered these days any form of development would be prohibited by law.

I read your link, and am as confused as ever. The definition of species that I was taught in school had elements of restrictedness of reproduction as well as structural and morphological components. I'm not jumping into any discussion of species here because I feel it is futile at best. There are too many opinions muddying the waters.

Rose: I'd never accept that if I didn't agree with it. ;-)

Ah. But scientists are still prepared to put many species between Australopithecus and modern humans using very variable definitions.

If you can name a singles bar with an Australopithecine I've no doubt I can find multiple applicants willing to test whether than male or female creature is a member of our species.

Though you might have to wait until closing time.

DA. I cannot actually remember attending a party where an australopithecus was present but I may have. I can't remember much of some parties.

It would actually be interesting to know how far back we would have to go before we reached an ancestor modern humans could not form fertile hybrids with. Although it's not totally a function of time, for most pairs of mammal species one million years is not sufficien. Beyond that infertility appears in the male offspring. By two or three million years both sexes are infertile. Beyond four million no offspring at all.

In spite of artists efforts we actually have no idea when the modern human hair pattern developed. Perhaps it had happened by Australopithecus times, especially in the tropical populations. There is a saying in NZ you don't look at the fireplace when you stoke the fire. Australopithecus females may have been quite cute. The males seem to have been big and fierce but many women today are attracted by that sort of thing.

TNZ wrote:
"I cannot actually remember attending a party where an australopithecus was present but I may have."

I went to a few parties like that when I was younger. Though I can still recall a few with Neandertals. <g>