In certain reptiles like snakes and chameleons, both a hormone called ghrelin and the enzyme that turns it on have disappeared together over time — as if nature turned off the whole system at once.

Scientists found that certain reptiles—like snakes, chameleons, and toadhead agamas—don’t have the gene that makes the ‘hunger hormone’ ghrelin, which means they probably lost it over time as they evolved.

Snakes don’t have the genetic instructions to make a hunger hormone that other reptiles like crocodiles and chameleons do have.