The blindsnake, a small subsurface burrower, is not often seen, but when it is many mistake it for a worm.1 Researchers have constructed an evolutionary history for these creatures, partly from biological data and partly from evolutionary assumptions. But if events occurred as these scientists suggest, then blindsnakes must have made fantastic voyages across vast oceans to reach their current habitats.
In a study published online in the Royal Society’s Biology Letters, researchers from Pennsylvania State University and other institutions burrowed into DNA sequence data from five genes found in 96 different species of blindsnakes in order to establish evolutionary relationships between the species.2 They used molecular clocks–which are far from objective and yield inherently biased results3–to decide when one group split from another.
The gene differences were all assumed to have been caused by mutation, and the gene data was fitted into an algorithm that presumed that all the blindsnakes shared a common ancestor. The study’s results presented a significant problem. When the dates assigned to the species’ divergence are compared to the prevailing theories of continental drift, certain families of blindsnakes must have developed after the combined land mass of Madagascar and India (dubbed “Indigascar” by the researchers) broke away from East Gondwana, which had earlier split from Gondwana, an ancient supercontinent.
A Penn State press release stated the problem succinctly: If the earliest blindsnake lineages developed on Indigascar, as the Biology Letters study claims, “how did they get to all of those other places in the world that they occupy today–Europe, Asia, Australia, Africa, and the Americas?” They infrequently venture up to the earth’s surface and are not known to swim at all. The press release stated that the researchers’ results led them to conclude that blindsnakes distributed themselves across the globe on “flotsam”:
The period of greatest diversification coincided with a time of low sea levels, when connections between continents were forming and the dispersal of such unlikely animals by floating on flotsam was easier.4
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