Ancestor of Snakes And Lizards Gave Birth To Live Offspring

Ancestors of snakes and lizards didn't lay eggs but gave birth to live offspring, a new study found.

The species were able to shift between their preferred reproductive modes and finally settled for laying eggs, a press statement revealed.

"This is a very unusual and controversial finding, and a major overturn of an accepted school of thought," said Alex Pyron, Robert F. Griggs Assistant Professor of Biology at the George Washington University. "Before, researchers long assumed that the ancestor of snakes and lizards laid eggs, and that if a species switched to live birth, it never reverted back. We found this wasn't the case."

The recent discovery revealed that live birth was an effective reproduction strategy way before previously believed. It also gave researchers a better understanding of this reproductive mode, suggesting it evolved 175 million years ago.

Other recent findings of plesiosaur and mosasaur fossils of lizards from the Cretaceous Period, which had embryos in the mother, supported the recent discovery of live birth among ancestral lizards and snakes.  

For the study, researchers looked at the evolutionary tree of these reptiles. They used DNA sequencing technology to group thousands of lizards and snakes and found that 115 groups of lizards and snakes, or about 2,000 species, have live birth.

Dr. Pyron now plans on analyzing evolutionary trees of tetrapods to see if they also adopted any other reproductive mode in the past. He also wants to test and see the genetics that allow certain species to shift between reproductive modes.