Thursday, May 13, 2010

Filling in the Gaps

Anti-evolutionists will not be trumpeting this news to their faithful fundies, I don't think. Irish study fills gap in evolution describes a new fossil find, not just a single fossil, but a site that is providing thousands of fossils documenting a stretch early evolution that has not been studied before. As the article reports, fossils of soft-bodied animals are extremely rare. This is because the conditions that will preserve a soft body are extremely rare. Only when the soft bodies are captured in some kind of muck which stops decay and then the muck turns into something like shale do we get to see what these ancient creatures looked like.

Those critical of evolution like to claim that the fossil record is incomplete. They say that as if it were not completely expected and explainable. As described in my previous post, the fossil record shows steady, slow evolution of many species, as well as relatively fast spurts of evolution. What gaps exist are not because intermediate creatures did not exist, but because they were not preserved in fossils or because we have yet to discover where they are preserved.

When new fossils are found, they provide a kind of lab in which to test evolutionary theory (not that more tests are needed, but that is what science always does with new information). We look at what we find and ask if it is consistent with theory. In this case, the fossils found in Morocco show life about 480 million years ago. Another site preserving such soft-bodied species dates back 510 million years ago. If evolution is correct we expect to find some creatures essentially unchanged even over 30 million years. But we also expect some creatures to have evolved to take advantage of new ecological niches.

That is exactly what is being found in the Fezouata Formations in the Draa Valley north of Zagora in southeastern Morocco.

“We know the fossil record is an important record of life, but it is an incomplete record,” says [Dr. Patrick] Orr. It makes interpretation of the progress of evolution very difficult, akin to trying to assemble the plot of a film using only intermittent still images, he suggests.

There was an explosion of new life forms during the Cambrian Period, with the shales revealing soft-bodied animals, according to Orr, “and then the record went blank.”

Now the evolutionary story continues with the Moroccan fossils showing that many of these Cambrian animals survived and multiplied into the next period, the Ordovician. The original animals were there but the Ordovician Period saw a rapid diversification of related species and so the mix is much more varied, Orr says.

This kind of filling in of gaps has been going on since scientists began hunting for fossils. Sometimes a new fossil location forces revision of the story that scientists had developed based on the then existing evidence. But this is a natural part of science. Such revisions are not to the theory of evolution, but to the details of what we are understanding evolution to have entailed.


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