Rattlesnakes have reduced their repertoire of venoms

Reptiles’ common ancestor possessed greater variety of toxic proteins

diamondback rattlesnake

STILL A FRIGHTFUL BITE  The venom of the western diamondback rattlesnake (shown here) isn’t neurotoxic — but its ancestor’s was. A loss of genes 4 million to 7 million years ago narrowed the range of toxins this and some other rattlers can use to kill prey. 

Audrey Snider-Bell/Shutterstock

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