The late Stephen J. Gould once wrote “Replay the tape [of evolution] a million times from a Burgess [the Burgess Shale fossils]beginning, and I doubt that anything like Homo sapiens would ever evolve again. It is, indeed, a wonderful life.” (Gould, Stephen J. [Professor of Zoology and Geology, Harvard University], “Wonderful Life: The Burgess Shale and the Nature of History,” [1989], Penguin: London, 1991, reprint, p.289. Well, maybe we wont’ have to replay the tape, because the tape of evolutionary history is getting replayed all the time, in the sense that lately it seems that every new discovery forces a complete re-write (re-wind?) of evolutionary history. Now we have a recent fossil discovery about to be reported in Nature shows that tetrapods may have crawled out of the seas way earlier than previously thought.
According to the article
A set of fossilized footprints show that the first tetrapods – a term applied to any four-footed animal with a spine – were treading open ground 397 million years ago, well before scientists thought they existed.
An expert unconnected with the research said the find would force experts to reconsider a critical period in evolution when sea-based vertebrates took their first steps toward becoming dinosaurs, mammals and – eventually – human beings.
“It blows the whole story out of the water, so to speak,” said Jenny Clack, a paleontologist at Cambridge University.
The work appears in Thursday’s issue of the journal Nature.
Despite Gould’s fantasy about rewinding tapes, it seems clear we’ve yet to see the first one correctly. In fact, as more and more discoveries like this one are forthcoming, it seems less and less likely that there even is an evolutionary tape to rewind, or if we even have the right tape. It will be interesting to see how this new find gets edited into the evolutionary tape.
UPDATED: Subsequent to posting this, I found this blogpost at Evolution News and Views written by Casey Luskin. Casey makes a good point regarding this new fossil find and its implications for the oft touted evolutionary link Tiktaalik.