VENOMOUS snakes evolved only once 60 million years ago from primitive python-like snakes that crush their prey, according to a study of toxins from over a hundred snake species.
The finding should settle debate about how often and how recently venomous snakes evolved. Some researchers believe venomous snakes evolved several times over the aeons, along with many lineages of snakes that are supposedly non-venomous, yet cannot crush their prey.
But Bryan Fry, deputy director of the University of Melbourne鈥檚 Australian Venom Research Unit, who ran the study, says almost all snakes that cannot crush prey poison it instead, and they have all evolved from the same ancient lineage. Fry reached his conclusions by using venom protein and DNA sequences to create an evolutionary tree. The results will appear in Molecular Biology and Evolution.
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Previously, experts had assumed that snakes that lack fangs also lack venom, confusing the picture of when venom evolved. 鈥淏ut venom evolved before fangs, and even snakes without highly developed fangs have potent venom,鈥� says Fry.
This explains why so many 鈥渉armless鈥� snakes have turned out on closer examination to be venomous. 鈥淭hey are not necessarily dangerous to humans, but they do have enough venom to settle a frog down,鈥� says Fry.