Dances with fruit flies
The Human Genome Project revealed a surprising fact: Despite our remarkable complexity and biological sophistication, human beings have just 25,000 or so genes, only twice as many as fruit flies and about the same number as other mammals and even fish. In a particularly interesting chapter on human evolution, Carroll notes that many of the differences between chimps and people--our slower development, larger brains, upright posture, and opposable thumbs, for example--represent changes in the size and shape of physical structures and the timing of development. We can't do fly-style experiments with humans, but Carroll presents a strong case that many of the key innovations that made us human lie not in our genes but in how we use them during development.
Beauty. Speaking recently in his office--a space so comfortably cluttered it almost resembles a nest--sporting shaggy hair and dressed in jeans and sneakers, Carroll seems about as content as a man can be. But the critics of evolution--he calls them deniers--are really starting to get under his skin. Like many scientists, Carroll sees no inherent contradiction between his work and a religious worldview. "I learned about Darwin and evolution from ordained teachers," says Carroll, a graduate of Catholic schools and the son of a composer of Gregorian chants. Science and religion are separate spheres, he says, and the temptation to live and let live is strong. But undermining the teaching of evolution in public schools would rob students of the chance to marvel at the beauty of the natural world, he says. "Your religious views are your own, but there is no more doubt about evolution than there is about cancer, kidney function, or volcanoes. If you reject science and deny evolution, you've picked a battle, and I'll fight it whenever and wherever I can."
Carroll hopes that the concrete steps revealed by evo devo will make evolution easier to understand for those who were confused by the abstract theories of the past and harder to refute by those who would deny its existence. (For one thing, the system of genetic controls that govern development and evolution is needlessly complex and clearly cobbled together from existing parts, Carroll notes. Surely any "intelligent designer" --an idea currently in vogue in some anti-evolutionary circles--who came up with the system would have been fired before the plans got to the blueprint stage.)
Evo devo is still a developing science, and many of its greatest advances are yet to come. The priorities, Carroll says, include understanding the basis of hard-wired behavior, like bird song and parental care, and working out the evolution of unique human attributes, such as speech and consciousness. And while further "proof" of evolution isn't a priority for scientists like Carroll, evo devo also holds the promise of not just revealing how the process works but actually re-creating some of its major steps in the lab. Ultimately, Carroll says, reaching this deeper understanding of nature--and our place in it--makes the biological realm more beautiful and inspiring, not less so. "There is mystery and wonder in the revelations of science," Carroll says, "and not being open to this is really missing a story that is fascinating and rewarding."
Born: Sept. 17, 1960 Family: Wife, Jamie; two sons and two stepsons Education: Ph.D. in immunology, Tufts Medical School, 1983 New book: Endless Forms Most Beautiful: The New Science of Evo Devo and the Making of the Animal Kingdom (W. W. Norton)
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