Episode Details

The evolution of venomous snakes was an incredibly complex journey that took hundreds of millions of years.

Here’s the short version of this interview (~45 minutes) … with much of the really technical scientific bits removed ….

And here’s the full-length version (over an hour) of our conversation with our guest expert. Buckle up your seat belts for this one, folks …

Dr. Bryan Fry, a world-renowned herpetologist unpacks for us the evolutionary journey that snakes have been on for the past couple hundred million years. 

We first compared what scientists can learn from the fossil record versus the genetic record.  Then we talked about how, when and why their predecessors lost their legs, and added a couple dozen vertebrae with ribs.  Spoiler alert: this involved DNA regulatory coding sequences called “sonic hedgehog” genes. 

The next major step in their evolutionary journey was the transformation of one or more of their salivary glands into a devious laboratory for the weaponization of otherwise normal proteins into a potent and lethal venom.  This venom doesn’t have to simply kill the prey: even just briefly stunning or paralyzing the prey is enough “to immobilize it long enough to swallow the prey whole and let it suffocate in the stomach.”

After that came the transformation of certain canine teeth into long, inwardly-curved, retractable and hollow fangs, to act like a syringe needle for that venom. 

Finally, we learned about a very recent evolutionary adaptation for snakes: a new behavioral response to the appearance of primates and humans on the evolutionary scene just a few million years ago, because those hominids had a nasty tendency of grabbing a stick and beating the snakes whenever the two species came into contact.  The snakes learned how to squirt their venom at those attackers, and then they revised  the venom to contain new components that induced intense pain (rather than paralyzing or killing the prey), which they then learned how to aim directly at the eyes of their attackers to ward them off!

Such an excellent case study in a variety of aspects of evolutionary theory: anatomical, biochemical and behavioral changes that result in exaptation … gene duplication … amplification … consolidation … and speciation.

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