Intelligent Reasoning


Saturday, March 10, 2012

Tiktaalik- Shubin Still Hasn't Found What He was Looking For

First, the set-up:
"In a nutshell, the 'fish–tetrapod transition' usually refers to the origin, from their fishy ancestors, of creatures with four legs bearing digits (fingers and toes), and with joints that permit the animals to walk on land. This event took place between about 385 and 360 million years ago toward the end of the period of time known as the Devonian. The Devonian is often referred to as the 'Age of Fishes,' as fish form the bulk of the vertebrate fossil record for this time."- Jennifer Clack, The Fish–Tetrapod Transition: New Fossils and Interpretations; "Evolution: Education and Outreach", 2009, Volume 2, Number 2, Pages 213-223

Got that- "the transition" refers to an event, a specific event that occurred between two specified time periods, a time when there were fish and no tetrapods and the time when there were fish and tetrapods. (as I said Here and again here- just can't get enough of RichTard's cowardice and ignorance)

With that now firmly established we return to "Your Inner Fish" chapter 1 where Shubin discusses what he was looking for- hint: evidence for the transition, ie the event:

Let's return to our problem of how to find relatives of the first fish to walk on land. In our grouping scheme, these creatures are somewhere between the "Everythings" and the "Everythings with limbs". Map this to what we know of the rocks, and there is strong geological evidence that the period from 380 million to 365 million years ago is the critical time. The younger rocks in that range, those about 360 million years old, include diverse kinds of fossilized animals that we would recognize as amphibians or reptiles. My colleague Jenny Clark at Cambridge University and others have uncovered amphibians from rocks in Greenland that are about 365 million years old. With their necks, their ears, and their four legs, they do not look like fish. But in rocks that are about 385 million years old, we find whole fish that look like, well, fish. They have fins. conical heads, and scales; and they have no necks. Given this, it is probably no great surprise that we should focus on rocks about 375 million years old to find evidence of the transition between fish and land-living animals.- Neil Subin pages 9-10 (bold and italics added)

OK he did it just exactly as described, bracketed the dates. However his dates were wrong, which means he did not find evidence for the transition, which occurred many millions of years earlier.

In order to find what he was looking for, evidence of the transition, he needed to focus on rocks 400 million years old, as the new data puts terapods in existence about 395 million years ago.

Tetrapod trackways from the early Middle Devonian period of Poland


Post a Comment

<< Home