Lizards rewind the evolutionary clock but end up the same every time

Ars Technica » Scientific Method 2013-07-22

There’s no doubt that we’ve come a long way in our understanding of evolution since Darwin's time. However, there's still a lot we don’t understand about the processes of natural selection, adaptation, and speciation. One question in particular still looms over the field: how predictable is evolution?

On one side, biologists such as Stephen Gould have long argued that evolution is “utterly unpredictable and quite unrepeatable” due to all sorts of historical accidents and perturbations. "Wind back the tape of life," he wrote, and "the chance becomes vanishingly small" that evolution would proceed in precisely the same way, creating the same set of species. However, in recent years, more and more research has suggested that evolution may actually be quite predictable. New research in the journal Science strengthens this argument by identifying a group of islands where Gould's tape has been wound back multiple times, and evolution has created a near-carbon copy almost every time.

The Greater Antilles are chock full of small lizards called anoles; there are anoles that specialize on twigs, on grasses, and on various parts of trees. Lizards on each island exploit these same niches, and across the entire island chain, anoles that use a particular niche look nearly identical. Grass specialists in Cuba are dead-ringers for those in Jamaica, and anoles that specialize on tree trunks in Puerto Rico could be mistaken for those in Hispaniola or Cuba. The kicker is that each of these islands was colonized separately by just one species of anole. In the forty million years since then, anoles on each island have independently adapted in near-identical ways, right down to the shapes of their tails and the stripes on their sides.

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