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Most Primitive Snake Fossil Discovered 77

smooth wombat writes "A newly discovered fossil seems to suggest that snakes evolved on land rather than in the water. The size of the fossil is unknown but it wasn't more than three feet long according to Hussam Zaher of the University of Sao Paulo in Brazil. It's the first time scientists have found a snake with a sacrum -- a bony feature supporting the pelvis -- he said. That feature was lost as snakes evolved from lizards, and since this is the only known snake that hasn't lost it, it must be the most primitive known, he said."
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Most Primitive Snake Fossil Discovered

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  • by jd ( 1658 ) <<moc.oohay> <ta> <kapimi>> on Thursday April 20, 2006 @12:23AM (#15162549) Homepage Journal
    There are older sea-living snakes that had legs - by about 9 or so million years, according to TFA. From this, we have several options, including that snakes evolved in the seas, came up on land and then LATER lost their legs. (This is an option NOT suggested by either of the two leading theories, but would seem to fit the facts the best.)

    The second option - the current leading theory - is that snakes evolved in the sea, lost their legs there, and that the snake found on land was some kind of genetic throwback, a branch that had nothing to do with the main line of snakes. This theory assumes that this find is NOT more primitive than the older fossils, but that the older fossils are more primitive by virtue of being considerably older.

    It does raise a number of problems, though, in that although there were sea-based snakes that did have legs, there is no evidence whatsoever that snakes ever evolved in the seas. The only reason this was seriously considered, in recent times, was that a precursor had to exist with legs, and the only snake fossils with legs that were known were all from aquatic deposits.

    The next-best theory is that snakes evolved on land and migrated back into the sea at a time when they still had legs. Migrations back into the ocean have happened - the Manatee had a common land ancestor with a Giraffe, and Cetaceans are believed to have evolved from a land-based fox-like creature. Such "reverse" migrations, then, have occurred before - probably quite a lot.

    The problem here is that, as I mentioned, the aquatic fossils are almost ten million years older. That's a LOT of time to account for, as it would require land snakes to have existed equally as long, plus enough extra to have a common ancestor that had evolved far enough to be identifiably a snake, plus as much additional time as needed to have forked off an aquatic branch of the family.

    No land-based snake fossils with legs have been found for the timeframe required. This doesn't necessarily mean a whole lot - snakes don't fossilize that well, not many people hunt fossil snakes, the odds of a discoverer realizing what they had AND publishing that fact are low, and since the aquatic theory held supreme, not many people were looking for those fossils in locations that would have been land at the time.

    On the other hand, it is extremely poor science to draw conclusions from evidence that is merely assumed to exist of an event that may never have happened at all. It is very easy to prove some pet theory, if you only ever have to assume the evidence might exist to do so.

    It is wrong to say that this recent find has helped anyone understand the evolution of snakes. The strongest statement that can be made is that it helps to establish where to look and what to look for.

  • Re: Biblical serpent (Score:5, Interesting)

    by Black Parrot ( 19622 ) on Thursday April 20, 2006 @01:46AM (#15162840)
    > Perhaps this discovery gives credence to the accuracy of the Bible.

    More likely the famous Genesis story incorporates a folk explanation for why some snakes have vestigal traces of walking apparatus.

    If you step back and look at it, most of Genesis consists of stories explaining why things are (and ought to be!) the way they are. It's a very common motif in mythologies and legendary histories from all over the world.

    The yarn about breeding sheep in front of striped staves to produce striped sheep, and the thrice-repeated "that's not my wife, that's ...uhm... my sister" meme (one guy fell for it twice!) should be all the hints you need that the book isn't a useful guide to biology or history.

egrep patterns are full regular expressions; it uses a fast deterministic algorithm that sometimes needs exponential space. -- unix manuals