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Discovery of "Oldest Fully Aquatic Whale" Fossil Throws a Major Bone into Whale Evolution Story

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tklarenb

tklarenb

In an article titled "Ancient whale jawbone found in Antarctica," the Associated Press reports that paleontologists have found "the oldest fully aquatic whale yet discovered," which is about 49 million years old. As we've discussed here on ENV in the past, whale evolution has faced problems because of the short timescale (~10 million years) allowed by the fossil record for whales to evolve from fully terrestrial mammals to fully aquatic whales. As Richard Sternberg has argued (see here, here or here), the many anatomical changes necessary to convert a land-mammal to a whale could not take place by Darwinian evolution even in 10 million years. There just isn't time. But this new fossil might imply that the amount of time available was actually less than 5 million years.

Until now, the whale series went something like this:

Pakicetids (fully terrestrial): ~50 mya
Ambulocetids (semi-aquatic): 49 mya
Remingtonocetids (semi-aquatic): 49 mya
Rodhocetus (a Protocetid, semi-aquatic): 47 mya
Basilosaurids (fully aquatic): 40 mya

So under the previous timeline, Darwinian biologists didn't have to worry about accounting for the origin of fully aquatic whales until about 40 mya. This new find pushes fully aquatic whales back to 49 mya. Now the timeline looks something like this:

Pakicetids (fully terrestrial): ~50 mya
New Fossil Jawbone (fully aquatic whale): 49 mya
Ambulocetids (semi-aquatic): 49 mya
Remingtonocetids (semi-aquatic): 49 mya
Rodhocetus (a Protocetid, semi-aquatic): 47 mya
Basilosaurids (fully aquatic): 40 mya

In light of this new find, it appears that fully aquatic whales existed at 49 mya -- around the same time that Ambulocetids appear. The fossil record now might jump from fully terrestrial Pakicetids to fully aquatic whales in just a couple million years -- maybe much less than 5 million years. In fact, if this find has been correctly identified, then fully aquatic whales might have existed before many of their alleged semi-aquatic evolutionary precursors. Of course future finds could extend these ranges, but if this fossil means fully aquatic whales existed as early as 49 mya, then the timescale available for whale evolution is incredibly short.

Under the old timescale, we were looking at about 400,000 generations for whale evolution. Now we're looking at much less than 200,000 generations -- far too little time to allow the origin and fixation of all the multitude of traits necessary to convert a land-mammal into a whale. The problem that Richard Sternberg has identified for whale evolution just got even worse.

http://www.spore.com/sporepedia#qry=usr-tklarenb%7C500646496436

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