Evolution in the News - March 1999
by Do-While Jones

Not a Leg to Stand On

Our most uninformed critic once claimed that since some snakes have small, non-functional bones where one would expect to find legs, that these snakes are a transitional form between eels and lizards. His argument is that these tiny bones evolved into fully functional legs, allowing the eel to move to dry land and evolve into a lizard. He thinks this is evidence of evolution in progress. It isn’t.

The journal Science summarized one of the papers presented at the annual meeting of the Society for Integrative and Comparative Biology, held in Denver from January 6 - 10, 1999, as follows:

How Snakes May Have Lost Their Legs
For centuries, not just scientists but artists too have speculated about the limblessness of snakes. Michelangelo thought the loss occurred in the garden of Eden. Now, two developmental biologists offer a less fanciful explanation-one involving genes and the proteins they produce-rather than divine intervention. 1

The article goes on to explain how biologists have found that chickens and snakes have similar HOX genes. In chickens, these HOX genes are responsible for making wings and legs. For some unknown reason, the HOX genes in snakes fail to function properly during development. According to Marty Cohen of the University of Reading in the United Kingdom, and Cheryll Tickel of the University of Dundee in Scotland, “the failure to develop complete hindlimbs seems to be due to an inability of the embryonic tissue to respond to the normal developmental trigger” because “the python ectoderm is not competent to respond to the signal.”

This is not evidence of evolution--it is evidence of regression. Snakes have lost some of the genetic information they used to have. It doesn’t show how snakes got the genetic information to make wings and legs in the first place.

All this research shows is that the ancient literature that describes winged serpents isn’t so fanciful and unscientific after all. Snakes did have wings and legs once. The evidence is still in their genes.

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Footnotes:

1 Elizabeth Pennisi, “How Snakes May Have Lost Their Legs” Science, Vol 283, 22 January 1999, page 475 (Ev)