Science a GoGo's Home Page Forums General Discussion General Science Discussion Forum Mammal rise 'not linked' to dinos

The extinction of the dinosaurs 65 million years ago had little effect on the evolution of mammals, according to a study in the journal Nature. One theory had suggested the rise of the mammals was directly linked to the disappearance of the dinosaurs. The evidence challenging the connection comes from the most complete family tree compiled for mammals. It shows how different groups, such as primates and rodents, are related and when they diverged. For the full story Click Here .

Thanks Dan. Can't seem to open the family tree.

The story was on radio news today. Presented as an "overthrowing of conventional theories" type story. I'm sure you know the type. "See, evolutionists can't even make up their minds". They did offer another slant on the story though. There seems to be a connection between mammals and the development of flowering plants. But I've been aware for years that the development of flowering plants, probably trees, was associated with the split in the mid-Cretaceous between the ancestors of monkeys and lemurs.

From the article:

"On the flipside, not all dinosaurs disappear at the end of the Cretaceous."

Raises the question; what did the asteroid destroy?

***IMO***

I think it knocked out the very large dinosaurs. As you know, some of them were so large that they literally spent every living second eating - even to the point where they lay eggs and just moved on and left them because they would decimate the vegetation in that area so quickly and need to move on.

I presume that these dinosaurs would be much more susceptible to the kind of environmental change that a large asteroid hit would bring. Any degree of scarcity would impact them heavily.

***IMO***

Blacknad.

You're probably correct Blacky. However about the same time there was an event that probably put even more rubbish into the atmosphere than did the asteroid. I mean the eruption if the Deccan plateau. It may even have contributed to the iridium layer. And we now know that dinosaur extinction was not completed within a single generation. It took 100,000 years or even a million. Could be associated with the general lowering of continents and rise of sea level throughout the Cretaceous period. Leads to the same thing though. Ultimately dinosaurs grew so big they ate themselves out of house and home.

A wikipedia link to Deccan traps:

http://en.wikipedia.org/wiki/Deccan_Traps

Anyway we can be fairly sure this extinction was not related to the presence of "two-legged semi-sentient primates". But wouldn't it be funny if a new theory came out that the development of monkeys after they separated from lemurs caused it? I have heard an old theory that the evolution of grasses was a factor.

Anyone want to speculate as to whether the Deccan eruption may have been triggered by the impact?

Take a good look at a map ... where is Yucatan ... where is India.

I know there are a lot of people saying no but I'm not that convinced.

DA. I'd agree it's certainly possible. However although India is sort of opposite Yucatan these days it wasn't 65,000,000 years ago. Still doesn't make the theory unlikely of course. I don't think the data is accurate enough yet to tell us which happened first. Perhaps the asteroid started the splitting of continents but I believe there is research that suggests the splitting had started in some places before this. I'll try to find relevant link eventually.

I'll reply to myself again, sorry. However nice series of maps of continental movement. The site is actually about evolution of ratites (large flightless birds) but does have a picture of continents at various stages. Map of what they call Late Cretaceous about halfway down the page, although at 90 million years I'd tend to call it Mid Cretaceous. As a memory aid you could say the Cretaceous lasted half the time between 130,000,000 years ago and today, ie began then and lasted until 65,000,000 years ago.

http://images.google.co.nz/imgres?imgurl=http://www.palaeos.com/Vertebrates/Units/350Aves/Images/Late-Cretaceous3.gif&imgrefurl=http://www.palaeos.com/Vertebrates/Units/350Aves/350.900.html&h=300&w=600&sz=45&hl=en&start=19&tbnid=bUIIb3Vo4Zfy0M:&tbnh=68&tbnw=135&prev=/images%3Fq%3Dcontinents%2Bcretaceous%26gbv%3D2%26svnum%3D10%26hl%3Den%26sa%3DG

And many of you may find this interesting although rather long. Deals with the KT extinction but almost belongs in the climate change thread. Suggests change in CO2, especially from the Deccan eruption, was the cause of extinctions.

http://filebox.vt.edu/artsci/geology/mclean/Dinosaur_Volcano_Extinction/pages/studentv.html

And another interesting, but long, one dealing with the problems in the catastrophe theory. Incidently says the eruption started before the asteroid hit.

http://www.ucmp.berkeley.edu/education/events/cowen1b.html

A comment from this last that I feel is very relevant:

"There are nagging fears that we are overstating the effects of the impact because the results are so clear in North America, close to the impact site."

TNZ wrote:
"As a memory aid you could say the Cretaceous lasted half the time between 130,000,000 years ago and today, ie began then and lasted until 65,000,000 years ago."

When multiple parts of the geological and biological record converge on 65M years ago there is reason to consider it not being a coincidence.

The fact that the eruptions started earlier does not mean they didn't get a good solid kick out of the earth being whacked. Consider the difference between stepping on an open and a closed tube of toothpaste. If the eruptions were already ongoing ... then there was already a path easily accessed to relieve the pressure.

I guess I'm not much of a believer in coincidence.

Quite possible Dan. The volcanism may have been boosted by the impact of the asteroid. But except for the divisions within the Tertiary all the boundaries between geological ages are defined by convergence of multiple parts of the geological and biological record. A whole series of events coincide at these points. So about 130,000,000 yeras ago something major happened as well. The extinction event at the KT boundary rates as about number five in severity. Statistical evolutionary changes define the divisions in the Tertiary.