U.S. biologists say they are studying the evolution of blindsnakes, often mistaken for earthworms, by examining the genetics of living species.

Pennsylvania State University Professor Blair Hedges, along with Nicolas Vidal of the French Museum of Natural History in Paris, are co-leaders of a team that discovered blindsnakes are one of the few groups of organisms that inhabited Madagascar when it broke from India about 100 million years ago, and are still living today.

The scientists said blindsnakes comprise about 260 different species and form the largest group of the world's worm-like snakes -- scolecophidians. The burrowing creatures, found mostly in southern continents and tropical islands, have reduced vision -- which is why they are called "blind."

Because there are nearly no known fossil blindsnakes, their evolution has been difficult to piece together, Hedges said.

In the recent study, the team investigated the evolution of blindsnakes by examining the genetics of living species.

They extracted five nuclear genes, which code for proteins, from 96 different species of worm-like snakes to reconstruct the branching pattern of their evolution, allowing the team to estimate the times of divergence of different lineages using molecular clocks.

"Our findings show that continental drift had a huge impact on blindsnake evolution," Vidal said, "by separating populations from each other as continents moved apart."

The study appears in the Royal Society journal Biology Letters.