In2-MeC

Kolhapur, Maharastra, India
10 April 2004

Kolhapur Deity Installation and Lecture at Homeopathic College
9, 10 April

 

 

 

 

 

...the portrait of homeopathy founder-acarya Hannemann. I got the honor of putting a garland on it!

 

Penn State Study Finds Origins of Snakes

Apr 9

By DAN LEWERENZ, Associated Press Writer

STATE COLLEGE, Pa. --Using DNA evidence, two Penn State University researchers think they have answered a long-standing question among scientists: Did snakes evolve from land-based lizards, or did they come from the sea?

In an article for the May 7 issue of the journal Biology Letters, Penn State biology professor Blair Hedges and postdoctoral scholar Nicolas Vidal write that the genetic evidence strongly suggests that snakes evolved from land-dwelling lizards. It's a conclusion that confirms a general trend in evolutionary biology, but bucks more than 100 years of thinking about reptiles, Hedges said.

The first tetrapods, or four-legged creatures, migrated from the oceans onto land 365 million years ago. Many animals later returned to the sea, including the ancestors of modern dolphins and whales--their arms and legs evolved into fins.

Herpetologists, though, have been divided about the origin of snakes. Some thought snakes evolved from land-based lizards, losing their legs to better squeeze through small holes and crevasses close to the ground. Others thought aquatic lizards, such as mosasaurs, made a second migration onto land as snakes.

Evidence for the aquatic theory came largely from physical similarities between monitor lizards such as the Komodo dragon--the closest living relatives of mosasaurs--and snakes.

"Monitors have these long, forked tongues like snakes, and not many other lizards have similar tongue morphology," Hedges said. "The body shape of a monitor is very long and snakelike. The jaws are very large and tending toward the snake's jaw type. So there were several lines of evidence, morphologically, that point toward a snake-monitor relationship. "

To test that theory, Vidal and Hedges compared the DNA from 17 of the 25 known families of snakes to DNA from all 19 families of lizards. They found snakes to be much more similar to land-based lizards than they were to monitors, providing strong evidence for a terrestrial evolution.

"In the last five or so years, people looking at gene sequences have claimed that they found support for a monitor-snake relationship in the sequence data," Hedges said. "But in all cases, they were missing many families of lizards, so I guess you could say the didn't have all the data to really say that for certain.

"When we had all of the families' data, it clearly showed there was no snake-monitor relationship. "

Although the evidence contradicts the strongly held beliefs of some herpetologists, Nancy J. Berner, associate professor and chair of biology at the University of the South, said the DNA comparison would be strong evidence for those looking strictly at physical similarities.

"The thing that really caught my attention, and that I think is really significant, is that the investigators were looking at genetic relatedness as opposed to anatomical structures," Berner said. "What this does is it's taking the new technology that's out there and applying it to an old question, really testing old theories. I would say that they're really on to something here. "

Although their research leads Hedges and Vidal away from the monitor lizards and the aquatic theory, they still haven't determined exactly where snakes began to separate from the lizard family tree.

"Now we need to identify the closest relative of snakes. We don't have it yet," Vidal said. "We can exclude monitors--that's statistically supported, strongly--so we know their origin is not marine. But all of the other lizard lineages are terrestrial, so we have to find which one. "

 

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