Scientists discover where snakes lived when they evolved into limbless...( using several statistical methods to d...)

using several statistical methods to determine how the species are related. "Although these genes have the same function in each species--and so, by definition, are the same gene--their structure in each species is slightly different because of mutations that have developed over time," Vidal explains. When the genetic comparisons were complete, Vidal and Hedges had a family tree showing the relationships of the species.

"Our results show clearly that snakes are not closely related to monitor lizards like the giant Komodo Dragon, which are the closest living relatives of the mosasaurs--the only known marine lizard living at the time that snakes evolved," Vidal says. "Because all the other lizards at that time lived on the land, our study provides strong evidence that snakes evolved on the land, not in the ocean."

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.

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Contact: Barbara K. Kennedy
science@psu.edu
814-863-4682
Penn State
30-Jan-2004

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