Darwin’s finches evolve before scientists’ eyes

A population of finches on the Galapagos Islands has been “caught in the act” of becoming a new species, according to the journal Science.

It reports that researchers saw the finches mixing with other birds to create a third species, in what is thought to be the first example of speciation observed directly in the field.

Finches on the Galapagos Islands consist of many species known collectively as Darwin's finches, which were first studied by Charles Darwin in the 1830s. The remoteness of the islands mean the animals that inhabit them have long provided insights into the mechanics of evolution.

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In 1981, researchers recorded the arrival of a male large cactus finch, a species not native to the islands. He “proceeded to mate with a female of one of the local species, a medium ground finch, producing fertile young”, the BBC reports. Thirty-six years later, their offspring are still being observed, numbering around 30 individuals.

The study “shows that reproductive isolation, which typically develops over hundreds of generations, can be established in only three”, the report in Science says.

“It's an extreme case of something we're coming to realise more generally over the years,” says Prof Roger Butlin, a speciation expert. “Evolution in general can happen very quickly.”