Pete Harcoff said:This is from the article, The pectoral fin of Tiktaalik roseae and the origin of the tetrapod limb:
Thanks, Pete. That's helpful and yet not.
Somewhere in this thread someone used the term "ill-suited" to describe the Tiktaalik forelimb's capacity for terrestrial life. I thought it was from the original link, but it wasn't, and I am not going to pursue it.
My concern was that shinbits reaction to this description (and any of the descriptions in the press articles) is that such conclusions are mere assumptions--that we have no way to know what the reality was.
But we do. By applying basic engineering principles to the structural form of an organism, we can deduce what it can and cannot do, including how much weight it can bear.
So, in this case we have a limb capable of limited excursions onto land. And that conclusion is not an assumption, but is derived from a detailed examination of the limb.
It is also clear that whatever its capacities to move about on land, it is essentially a fish, an aquatic animal, whose principal means of locomotion was swimming.
The new find of several specimens looks more like a land-dweller than the few other fossil fish known from the transitional period, and researchers speculate that it may have taken brief excursions out of the water.
From the Science link in post #1
Those limbs tell us something about the evolution of limbs. Tiktaalik was definitely not a terrestrial animal, but had developed muscular, bony limbs and a strong pectoral girdle that had helped it prop itself up on the substrate, perhaps even holding itself partly out of the water. Those jointed digits were capable of extension and flexion, splaying out when they were pressed against the ground.
From the Pharyngula link a few posts later.
So the take-home point is not whether Tiktaalik was able to move on land--that was never fundamentally in question--but that the conclusion that it did, that it was part of the process of adapting to terrestrial life, is not an assumption.
As the Pharyngula article points out:
"The limbs alone have a whole paper dedicated to them."
Personally, I detest reading primary literature in science. It's filled with numbers and graphs and technical terms I don't understand. What I do understand is that this is valuable evidence for other scientists to analyse. And that conclusions based on such expert analysis are not assumptions based on bias.
They are conclusions based on detailed study. And there is a good deal more that can be learned from study than most creationists are aware of.
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