Thursday, 31 October 2013

Finding Evolution's Missing Links

Evolution's detectives: Closing in on missing links - life - 19 February 2013 - New Scientist

'Missing links' are creationist's favourite gaps in which they try to fit their god. The great thing about them is that no matter how many fossils are found and no matter how complete an evolutionary sequence they make, creationist frauds can always point to the gap between two adjacent fossils in the series and claim it as their 'missing' link. In fact, every fossil ever found is of course part of an evolutionary series and is the 'missing' link of its generation, but it simply serves to double the number of gaps for creationists.

This article in New Scientist from last February, which unfortunately is behind a paywall, goes into great detail about the key stages in the evolution of life which need to be evidenced by the fossil record, and attempts currently being made to find that evidence. Evolutionary biologists, like other scientists, are not at all embarrassed by the "don't know" answer. In fact, it's knowing what you don't know that drives enquiry and makes science such an interesting and fascinating subject for most people who don't need absolute certainty in their lives and who don't need to pretend they have all the answers (or should that be 'answer', because it's always the same one - "God did it!" - which can be glibly and smugly trotted out in the hope of impressing people with your expertise).

What struck me especially was a brief mention of how one of these missing fossils was discovered because it is as good an example as you're likely to find of the Theory of Evolution making a falsifiable prediction which was then completely validated. This is the standard scientific technique for validating hypotheses, of course.

The missing fossil record was of the evolution from lobe-finned fish to the limbed tetrapods which were then able to colonise the land. This key step in the evolution of terrestrial vertebrates and so in the evolution of humans was estimated to have occurred about 375 million years ago, so the hypothesis to be tested was fairly straightforward - there should be 'transitional' fossils showing this stage in evolution in sedimentary rocks deposited about 375 million years ago.

So, Ted Daeschler of the Academy of Natural Sciences in Philadelphia, PA, USA and Neil Shubin from the University of Chicago, IL, USA scoured the geological maps looking for surface rocks of the right type and age and found just the right formation in the Canadian Arctic on Ellesmere Island. Work on the site was only possible during the summer so it took four summers of searching before they found what the theory said should be there. They found a fossil they called Tiktaalik.

Tiktaalik was a great example of a prediction that you could make and go out and validate

Ted Daeschler
Tiktaalik, which is Inuktitut for 'burbot', a freshwater relative of the cod, had limbs which were exactly what the theory predicted, midway between the fins of the lobe-finned fish and the limbs of tetrapod amphibians with typical bones that make up a standard terrestrial vertebrate limb all easily identifiable and arranged according to the standard arrangement. And the fossil was found in rocks of the right type and the right age, just as predicted. A falsifiable prediction made by the Theory of Evolution had been confirmed.

Of course, the standard creationist response will be that there are now two gaps in which to sit their god, but they have to sit their ever-diminishing little god somewhere.

Further reading:
Wikipedia - Tiktaalik

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