Researchers at Yale University recently delved into the evolutionary history of snakes, and what they discovered was an ancient creature who lived over 120 million years ago in the warm forests of the Southern Hemisphere. And most interesting of all, this creature sported tiny hindlimbs, replete with ankles and toes.
The researchers at Yale set out to construct the first family tree that traces the evolution of snakes back to their original ancestor. They were curious about the evolutionary history of these incredibly diverse creatures, which today include over 3,000 species that inhabit a wide range of ecosystems around the globe.
Allison Hsiang, a postdoctoral researcher of geology and geophysics at Yale University and lead author of the study, said, "While snake origins have been debated for a long time, this is the first time these hypotheses have been tested thoroughly using cutting-edge methods. By analyzing the genes, fossils and anatomy of 73 different snake and lizard species, both living and extinct, we've managed to generate the first comprehensive reconstruction of what the ancestral snake was like."
They began by sorting through similarities and differences between snake species in order to pinpoint some of the major characteristics (and their associated genes) that arose during their evolution. By tracing these characteristics back through time, they were able to reconstruct a time table for the snake's appearance. Their comprehensive analysis points to the middle Early Cretaceous period, around 128 million years ago, most likely on the supercontinent of Laurasia, which at that time included parts of North America, Europe, and Asia.
Their research also suggests that the earliest snakes were nocturnal and that the shift to diurnal (daytime) habits, which occurred around 45-50 million years ago, coincided with the appearance of Colubroidea, which today make up over 85% of living snake species.
And what about those limbs? It's believed snakes evolved from lizards and simply lost their limbs over time. Hsiang's research indicates this occurred on land as opposed to in water, a matter that has been debated for some time among paleontologists.
Despite the loss of their tiny limbs, snakes are agile dispersers, which may account for their evolutionary success. They can range up to 110,000 square kilometers - about four times that of their limbed cousins, the lizards, and today occupy lakes, forests, deserts, and swamps.
Thanks to Yale's research, we now have a better understanding of when and where snakes arose and how they evolved over time.