Darwin Primers for the Doubters

David Brown covers science and medicine for the Washington Post ...

He's reviewed two books with similar --- and fascinating --- premises. Specifically, people with conservative views should embrace the prime theory of Charles Darwin, which is that natural selection is the way of the world. That most don't is one of life's little ironies.

"The Reluctant Mr. Darwin: An Intimate Portrait of Charles Darwin and the Making of His Theory of Evolution"
by David Quammen
Norton, 304 pp., $22.95

"Why Darwin Matters: The Case Against Intelligent Design"
by Michael Shermer
Times, 199 pp., $22

Evolution isn't hard to understand; you don't need to know about thermodynamics or the unique property of the speed of light. Evidence for it is part of ordinary life, visible in both the general similarity of many organisms and the crucial differences between them.

So why do people have such a hard time accepting evolution and its engine, natural selection?

These two wonderful books try to explain why such a richly documented and proven theory (by science's standard, which allows no certain proof outside mathematics) remains so difficult for some people.

"The Reluctant Mr. Darwin" lays out the conditions, both personal and cultural, that allowed the brainstorm of natural selection to hit Charles Darwin and Alfred Russel Wallace, two Englishmen, more or less simultaneously in the late 1850s. David Quammen begins his story with Darwin's return to England in 1836 after five years wandering with the survey ship HMS Beagle. Quammen's book is about the birth of an idea, seen through the life of the person who birthed it.

And a long gestation it was. It took Darwin more than two decades to make sense of what he'd seen and collected, to formulate his theory, test its key features, and write it up and publish it, in 1859, as the epochal "On the Origin of Species." It's an agonizing story of procrastination and perfectionism that left Darwin in a dead heat with Wallace, a younger and less patient man.

Darwin made several important observations soon after arriving home. He'd found in several places a large number of similar-appearing species, such as the now-famous finches of the Galapagos, each with a differently shaped beak. He noticed that physical isolation appeared to go hand-in-hand with those differences and with "speciation," the division of living things into distinct, non-interbreeding populations. He also noticed that fossils of extinct species were often found in places where animals that resembled them now lived.

In a series of secret notebooks, Darwin charted his growing belief that species were not fixed but transmutable. He intuited that they arose from common, extinct ancestors. But how could this happen? He needed at least two more insights to answer the question.

One came from the parson-economist Thomas Malthus, who calculated that animal and plant populations always reproduce faster than their food supplies grow, ensuring that far more of every species will be born than will make it to adulthood. Competition and death on a massive scale are unavoidable features of life, Malthus observed. The other idea Darwin needed was that individual organisms differ recognizably from each other even when they are of the same species.

As Darwin plodded, Wallace was charging along. His teacher was the Amazon, and he learned more quickly than Darwin. Wallace financed his trip by sending skins of tropical birds and other exotica back to rich collectors in Britain.

Quammen writes: "Darwin needed eight years with barnacles, following five years of travel and ten years of study, to awaken him about variation in the wild. Wallace saw it sooner because, besides being an alert observer, he was a commercial collector, hungry and broke."

In their own ways, both men put the pieces together: Tiny variations, arising randomly and pointlessly, occur among individual organisms. In a few cases, those changes make a difference in an individual's ability to compete for food, habitat and mates. Such an individual is more likely to have offspring, or at least to have more of them. Over time, the population with that adaptive change grows. Over a very long time, it may become a new species, distinct from its ancestors.

Three papers encapsulating this incendiary theory -- two by Darwin, one by Wallace -- were read to the Linnean Society in London on July 1, 1858. The rest is history ... and present-day politics, cultural struggle, religious controversy and jurisprudence, which is where Michael Shermer picks up the story.

A historian of science and a columnist for Scientific American magazine, Shermer lays out the case for evolution cogently, if not in great detail, in "Why Darwin Matters." He then does what many scientists are unwilling to do: He engages and answers the arguments of people who don't accept evolution. He does this with care and respect but without any false evenhandedness.

It has always been hard for some people of faith to accept that nature's marvelous complexity could be the product of natural selection -- a passive process incapable of intent and unguided by any divine hand. Nevertheless, the evidence for evolution is everywhere. As Shermer puts it, "While the specifics of evolution -- how quickly it happens, what triggers species change, at which level of the organism it occurs -- are still being studied and unraveled, the general theory of evolution is the most tested in science over the past century and a half. Scientists agree: Evolution happened."

With zest but without gloating, Shermer takes on the arguments against evolution and mows them down.

He also addresses the hidden agenda of "intelligent design," which he says is the promotion of religion in general and fundamentalist Christianity in particular.

In a bit of his own proselytizing, Shermer tries to show why political and social conservatives should actually embrace Darwin's discovery, not vilify it. Evolution has given rise to species (and not just our own) that value social cooperation, monogamy and altruism -- the very values so many conservatives feel are threatened by the secular world. Natural selection, he writes, "is precisely parallel to Adam Smith's theory of the invisible hand" -- a process whereby self-interest creates order and a self-correcting whole that is larger than any of its parts.

This last argument -- evolution as the natural world's equivalent of free-market economics -- is a heroic attempt to make Darwin's idea more palatable to some of its detractors. But purely on the evidence, evolution is an idea that hasn't needed special pleading for a very long time.