Charles Darwin is widely thought to have developed his natural selection theory of evolution after noting differences among finches in the Galapagos Islands.
But it was variation in another species the young British naturalist observed during his now-famous voyage on the HMS Beagle - man - that actually drove his breakthrough, a new book argues. And the inspiration for that insight may well have been Darwin's fervent anti-slavery views and moral passion to show that men of all races were brothers.
"Everyone says the Galapagos are everything, which is more or less rubbish," said James Moore, a Darwin biographer and co-author of the new book. "For Darwin, humans are the starting point."
Two hundred years after his birth and 150 years after the publication of his landmark book, "On the Origin of Species," Darwin remains one of the world's most influential scientists, a thinker whose revolutionary ideas _ like those of Albert Einstein or Isaac Newton - have largely stood the test of time. But Darwin's ideas simultaneously remain at the center of deep philosophical and religious debate a century and a half after they were published.
Britain marks Darwin's anniversaries this year with the release of a new 2 pound coin, featuring Darwin face-to-face with a chimpanzee, the launch of a Darwin festival at the University of Cambridge in July and tours of Darwin's reopened family home in Orpington, southeast of London.
But even as Darwin's life and legacy are celebrated, half of British adults say they don't believe in Darwin's theory of evolution or are confused about it in some way. In the United States, more than half either reject the theory or insist God guides the process of evolution.
"Why did Darwin touch the untouchable" by developing a theory that "was an abomination to a Christian gentleman naturalist who needed career advancement and respect?" asks Moore, who holds degrees in divinity, history and science.
The answer, he argues, is basically that Darwin, raised in a family that considered slavery a sin, believed wholeheartedly in "the brotherhood of the races" and was able to imagine a family tree that united them and the mechanisms that led to their differences, unlike other thinkers of his time.
"He was quite unlike the modern 'disinterested' scientist who is supposed ... to derive theories from 'the facts,' " Moore and co-author Adrian Desmond suggest in their book "Darwin's Sacred Cause."
But at the same time, Darwin "was the reverse of the fundamentalists' parody, which makes his enterprise anti-God, inhuman and immoral," the book says.
Moore, 61, the grandchild of two evangelical preachers - one Baptist, one Methodist - knows something about negotiating the tensions between religion and science.
Raised in Chicago in a large "arch-fundamentalist, real Bible-banging, flag-waving" family, he studied science and engineering "with a view to advancing the Christian ethic" and saw Darwin as an enemy.
But the Vietnam War shook his religious foundations, and a Marshall Scholarship at Manchester University in Britain, with the space it brought from his family, "freed me to think for myself," he says.
He wrote a doctoral dissertation on the controversies provoked by Darwin's work, became involved in the leftist liberation theology movement, which argued that churches had a moral obligation to step into politics to assist the oppressed, and eventually became an admirer of Darwin and one of his most active biographers.
The new book, which Moore calls a "prequel" to his and Desmond's 1991 biography, "Darwin," was inspired by a hunch about the reasons the naturalist pursued his radical theory of evolution. Moore, who now lives in Cambridge, knew Darwin came from a family strongly opposed to slavery and one that believed that all human races were genealogically related.
At the time, many of their contemporaries thought the world's races had taken separate evolutionary paths rather than springing from the same tree.
Recent digitalization of old records in Britain, particularly ship logs from Darwin's five-year journey on the Beagle as well as family letters and journals, also shed light on his firsthand encounters with slavery, his growing awareness of the range and adaptability of humans, and his recognition that widespread struggle existed among people and races from South Africa to Tahiti to Tierra del Fuego.
Those experiences may well have led to his breakthrough that evolutionary change was driven by competition for survival, a mechanism he called "natural selection."
In fact, documents show that the differences between Darwin's Galapagos finches were pointed out to him by a colleague only months after he got back from his famous voyage. Darwin hadn't bothered to note his bird samples came from different islands, Moore says.
But the finches became one of the leading examples of his theory because "he realizes he has a beautiful illustration of what he's working on," Moore says - and because he knows using human variation to illustrate his theory would cause an uproar and likely lead to his work being condemned and rejected.
The new theories about Darwin's moral motivations for his science have sparked discomfort both among scientists, who fear they undermine the purity of his work, and creationists, who may find themselves with more in common with an old foil than they had imagined. A Vatican official confirmed this week that Darwin's theories were compatible with Christian belief.
"There has been great reluctance to see Darwin as more than a heroic genius uncovering pure gems of truth," Moore said. "This throws all Darwin's work - so vilified for being morally subversive - into an entirely different light."
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