Around the world, in a range of different environments, pythons and boas resemble each other. A new study reveals that these commonalities come not from common ancestry, but because the two families of snakes found similar solutions to the same problems, a process known as convergent evolution.
In wetlands and forests, pythons prey on small mammals, birds, and frogs. To the untrained observer, an aquatic python looks more like an aquatic boa than a tree python. Nevertheless, the reason we classify all the pythons as one family and boas as another, is because they each descended from a common ancestor not shared with anyone else, rather than just lumping species together because they resemble each other.
In many different environments pythons and boas adapt in such similar ways they can be hard to tell apart. Damien Esquerre.
Australian National University PhD student Damien Esquerre compared the head shape of 1,073 specimens from 34 species of pythons and 45 boas, to show how, when confronted with matching environments, each went for remarkably similar solutions. He measured head shape, because in a limbless predator like a snake, it is an extremely important feature.
“People in the past thought pythons and boas were part of the same family,” Esquerre told IFLScience. “But DNA shows their last common ancestor was 70 million years ago, during the age of the dinosaurs. Their closest living relatives are small and burrowing snakes that don't look anything like either.”
Examples of convergent evolution are common, but in Ecology Letters Esquerre points out: “Such cases often are based on general similarities in appearance (e.g. numbats and anteaters or wolves and thylacines in the comparison between the radiations of placental and marsupial mammals), rather than rigorous quantitative similarities.”