04/28/14

Seeing evolution in action


Peter and Rosemary GrantThe pop-science notion is that evolution takes a long time. Millennia, many millennia; even millions of years. But is that always true? Can one actually see and measure evolution in action? Can it happen in such a short time as to be recorded?

Peter and Rosemary Grant say they have. And it’s the subject of a new book they co-authored based on their research.

Their story was reported in the April 23 issue of the Princeton Alumni Weekly. It’s a terrific read if for nothing more than their 40-year tale of dedication, science and adventure on the isolated Daphne Major Island, one of the smaller islands of the Galapagos chain.

Forty years studying finches together, away from human company, away from the comforts of civilization. The small birds that first gave Charles Darwin insight into the mechanics of natural selection were their focus. And the Grants report they have seen that mechanism in action on the island.

Scientists previously had reported seeing the processes of natural selection among bacteria, honeycreepers, cichlid fish, and fruit flies. As Peter Grant puts it, “Until we began, it was well understood that agricultural pests and bacteria could evolve rapidly, but I doubt that many people thought that about big, vertebrate animals.”

The Grants believe that hybridization is an important force in the rise of new species, and think this applies, too, to human evolution. For a long time, for example, paleontologists believed that Neanderthals and “modern homo sapiens” did not interbreed when they came into contact in prehistoric times, but recent research indicates that about 20 percent of Neanderthal genes have been preserved in our species. “It’s almost been a hobbyhorse of ours,” Peter says. “We were saying, ‘I bet there has been gene exchange between the lineages of homo sapiens throughout their evolution.’”

The Grants’ new book is targeted at both lay readers and scientists familiar with their work, and broadly discusses their findings about natural selection, hybridization, population variation (why do some populations of birds vary more dramatically in beak size?), the potential vanishing of a species through interbreeding, and, of course, the potential origin of a new species — the Big Bird lineage. They also touch on global warming and its possible effect on Darwin’s finches. Most of all, the book is an affirmation of the importance of long-term fieldwork as a way of capturing the true dynamism of evolution.

Continue reading