Evolution's Evolution: Darwin's Dangerous Idea Has Adapted to Modern Biology

Article excerpt

Just a decade after he published On the Origin of Species, Charles Darwin was already worrying about the evolution of his idea. In an 1869 letter to botanist Joseph Dalton Hooker, Darwin lamented: "If I lived twenty more years and was able to work, how I should have to modify the Origin, and how much the views on all points will have to be modified! Well, it is a beginning, and that is something."

Calling the Origin a mere "beginning" is like saying the Beatles were just a rock band or that Shakespeare wrote some decent plays. Darwin's gifts to science were radical. He not only proposed that Earth's beings all shared a common ancestry, but also described an elegant mechanism to explain how all that diverse life came to be. Darwin was a master of merging data from different disciplines, painstakingly drawing from zoology, botany, geology and paleontology to build a solid foundation for evolutionary biology. Today, 150 years later, scientists continue to grapple with ideas descended from that foundation. Still, Darwin's central tenets survive, fit enough to frame the questions posed by modern biology.

"He had great intuition," says Yale University's Michael Donoghue. "He's the guy we all envy."

Darwin's powers of observation and reason extended from microflora to megafauna; he could see the whole forest while scrutinizing the branches on the trees. His ideas illuminated life's development in the Earth's deep past and foreshadowed many scientific developments to come, including the refinements to his theory that scientists are still exploring. Yet were Darwin alive today, his head might spin at the complexities entangling the expansion of his original ideas.

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Evolutionary theory is not a well-preserved fossil in a dusty museum, but a thriving field of study in labs, on beaches and in bogs. The exploding research program known as "evo-devo," for instance, has wed evolutionary theory to embryology and genetics, helping to unravel the evolution of organisms' structures and forms. Scientists are also reformulating ideas about evolution's pace, showing that Darwin's idea that change happens gradually doesn't always capture the whole story. Researchers are fleshing out Darwin's central idea of natural selection--discovering when it's the driver and when it takes a back seat. And along with investigating how selection operates on organisms--Darwin's unit of choice--scientists are also showing how it acts on groups, genes and behavior. Experts are even still debating the very definition of "species."

If Darwin came back, "in some ways he would be mystified," says evolutionary biologist Douglas Futuyma of Stony Brook University in New York. "Evolutionary biology has been radically changed--and deeply enriched."

Like confessing a murder of course, Darwin was familiar with radical change. In his day most biologists (or "naturalists," then) believed that each species was individually created and forever immutable. But during his travels in the 1830s on her majesty's ship the Beagle, Darwin saw plants and animals and fossils--and distributions of all three--that just didn't square with the idea that species don't change.

By 1844 Darwin had accepted the unacceptable and wrote to Hooker: "At last gleams of light have come and I am almost convinced (quite contrary to the opinion I started with) that species are not (it is like confessing a murder) immutable."

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Subversive as it was, Darwin's proposal that species can change was not the first. In the late 1700s, French naturalist Georges Cuvier had established that after great environmental change, some organisms got snuffed out, went kaput, extinct. A little later, zoologist Jean Baptiste Lamarck proposed the notion of adaptation, explaining variation among organisms as a response to their environments.

But Darwin (and later Alfred Russel Wallace, independently) saw that life's variation could arise from the struggle to survive among competing organisms. …