How Snakes Lost Their Limbs
Penn State scientists have a story for how snakes, which presumably evolved from lizards, lost their legs. They had to burrow through tight places.
Part of their story involved disproving that snakes evolved from sea-going reptiles, like mosasaurs, explains the press release from Penn State’s Eberly College of Science. They compared genes from 64 species of lizards and snakes. Since no mosasaurs exist today, they took genes from Komodo dragons, their assumed closest living relatives. They feel their comparisons show that snakes evolved from land-dwelling lizards.
So why would a land lizard want to lose its feet?
The research suggests an answer to another long-debated question: why snakes lost their limbs. Their land-based lifestyle, including burrowing underground at least some of the time, may be the reason. “Having limbs is a real problem if you need to fit through small openings underground, as anybody who has tried exploring in caves knows,” Hedges says. “Your body could fit through much smaller openings if you did not have the wide shoulders and pelvis that support your limbs.” The researchers note that the burrowing lifestyle of many other species, including legless lizards, is correlated with the complete loss of limbs or the evolution of very small limbs.
The research, to be published in the May 7, 2004 issue of the Royal Society’s Biology Letters, was funded in part by NASA’s Astrobiology Institute and by the National Science Foundation.
Better not explore caves if you want your kids to have legs. Why do some lizards still crawl into tight places tighter than a big snake could pass? Why do gophers and weasels have legs? Is limb loss really evolution? The quote of the month (see top right box on this page) says it all.