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Westminster Abbey is a Gothic and cavernous place of cloisters, chambers, nooks, and crannies that has served as Britain's royal crowning place and national ossuary since the time of William the Conqueror, a thousand years ago. Adjacent to the House of Commons in London, the abbey, now a UNESCO World Heritage Site, is filled with statues of generals, monuments to statesmen, poets, and martyrs, and the chest tombs of dead kings and queens.

There is also a humble white marble slab, on the floor of the north side of the nave, near the quire. It's easy to miss because it's in a kind of corner, where it's dark, and it's also almost in the shadow of a garishly splendid monument to Sir Isaac Newton, which tends to hold the visitor's attention.

But if you look for it, you'll find it easily enough.

Charles Robert Darwin. Born 12 February 1809. Died 19 April 1882.

No stirring elegy. No moving psalm.

Just that.

I'd gone to see that marble slab recently, partly because I just never had, and partly because it had been occurring to me for some while that of all the great thinkers among the Enlightenment's first-born, from John Stuart Mill to Karl Marx, there was no one whose star still shines as bright in the firmament as Darwin's. Of them all, Darwin remains indispensable. But not, oddly enough, for his work as a scientist.

Darwin was a great scientist, of course. He made important contributions to natural history, and even geology, but his most important contribution was not, strictly speaking, a scientific achievement.

It was a way of explaining the "mystery of mysteries", the origin and diversity of the world's living things. But Darwin's On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life presents not a single case of evolution by natural selection. Instead, it was, in Darwin's words, "one long argument".

It was a theory with no hard science, no firsthand observation, to back it up. It was a work of exposition and logic. What Darwin had going for him, though, was a fine command of plain language and a body of evidence developed over more than two decades of investigation, observation, and reflection.

Darwin's quarry was the deeply entrenched conviction that each of the Earth's myriad life forms was created by divine intervention only a few thousand years ago. Darwin argued that the living things of the world had evolved from, at most, a handful of ancestors of almost unimaginable antiquity.

Darwin wasn't alone in this heresy, but what distinguished his argument was the contention that evolution occurred by a process of minute variation in type and form, caused by natural factors that constantly "selected" those heritable traits in animals and plants that favour advantage and survival.

Evolution occurred at a glacial pace but it occurred nonetheless, and it was still going on, "daily and hourly", in life all around us, Darwin insisted. That was his resolution of the great mystery. God, maybe, but not necessarily. And, ultimately, it meant there was no reason to imagine that humanity was at the centre of any divine plan after all.

For the time, this was a very dangerous idea.

Darwin had gathered all manner of evidence from fossils, from pigeon breeders, and from his discoveries during his five-year tour as the naturalist aboard the survey ship HMS Beagle. But because evolution occurred so slowly, his thinking went, it wasn't possible to demonstrate its workings in case studies.

Darwin had his defenders and champions, and he also had in his corner the naturalist Alfred Russel Wallace, sometimes referred to as the "codiscoverer" of what came to be called Darwin's theory. But Wallace, too, despite years of fieldwork, relied on inference and logic to make his case, in the form of a table of "proved facts" and "necessary consequences".

Although Darwin could show that evolution by natural selection must be the answer, he couldn't present evidence for that answer in even a single case of evolution by natural selection, observed and documented in the "natural" world. No one, least of all Darwin, had ever seen it actually happen.

As a consequence, long after Darwin's theory had come to form the theoretical basis for the biological sciences, there was still an embarrassing dearth of experimental research into evolution. It was still, outside of science, just an "opinion". While Darwin explained how the "natural" world worked in theory, no one, even into the 1970s, had been able to fully and methodically document and describe having actually seen it work that way in practice.

This is where Peter and Rosemary Grant come in.

Peter and Rosemary, both from England, met at the University of British Columbia in 1960. They soon married, and both went on to work as professors of evolutionary biology at Princeton University. Now both 71, the Grants are among the most successful and important collaborations in the history of science. In 2005 they won the coveted Balzan Prize, which is equal in prestige to the Nobel Prize and brings almost three times the cash: the equivalent of about $3 million in Swiss francs.

The Grants have produced a body of research that is so exhaustive, so exacting and thorough, that many ornithologists fear it will never be replicated. The object of the Grants' obsessions is Galápagos finches. These are the birds so closely associated with Darwin that they're commonly called Darwin's finches.

It was Darwin's encounter with the archipelago's 13 finch species in 1835, during his five-week Galápagos sojourn as the naturalist aboard the Beagle, that caused his epiphany and produced evolution's great eureka moment. That's the legend, anyway.

The truth is it was long after his return to England, and after the specimens he'd collected had been properly classified by British taxonomists, that the significance of the birds, and of all those other peculiar endemic species he'd found on the Galápagos Islands, began to dawn on Darwin.

It wasn't until Peter and Rosemary Grant began making their annual pilgrimages to the Galápagos island of Daphne Major, a forbidding place of black lava and hellish summers, that the finches began to fully reveal themselves to science.

The Grants began their fieldwork on Daphne Major in 1973. They've put in 35 field seasons, and they're still at it. (The Grants will be presenting an overview of their most recent findings in a free lecture at the University of British Columbia on November 20.)

The Grants have documented the phenomenon that Darwin could only surmise by deduction and conjecture. It turns out that the mechanism of evolution can be observed moving through nature, not just in a laboratory or in a human-altered environment, and it doesn't always move at a glacial pace. The Grants have watched it happen, up close.



Biologists Rosemary and Peter Grant have spent 35 field seasons observing how natural selection has resulted in the evolution of Galápagos finches. Biologists Rosemary and Peter Grant have spent 35 field seasons observing how natural selection has resulted in the evolution of Galápagos finches.

Specifically, what Peter and Rosemary have done is present the world with a rare and dramatic glimpse of variation caused by natural selection from one generation of animals to the next. And down through several generations of Galápagos finches, from different species, they've shown how heritable traits are "selected" so as to result in evolution.

As evolution occurs, even when it occurs quickly, it's usually barely detectable. The tiniest change can mean survival or extinction. In the case of the Galápagos finches, what matters is often barely measurable changes in the size and shape of the finches' beaks.

"That's the really difficult thing to do," Peter told me the other day. "You don't want to try it with earthworms."

It isn't that Darwin's theory had not been shown to work in practice before the Grants. It's just that no one had documented it in nature so completely and methodically.

Before the Grants, the case of the English peppered moth was one of the best-known studies of natural selection driving evolution. But the story of the peppered moth unfolds in a completely human-altered environment. Its observed evolution was in response to the rise and decline of the Industrial Revolution.

Prior to the advent of the "dark satanic mills" and the clouds of coal smoke and ash that settled over the English countryside, peppered moths were light-coloured, with specks and streaks of black, a colour scheme suited perfectly to camouflage because of the moths' habit of alighting and resting on tree trunks, on similarly coloured lichens.

In the poisoned air of the Industrial Revolution, the lichens diminished in abundance and trees were commonly blackened with soot. This trend favoured a black-coloured mutation in peppered moths and caused the light-coloured moths to nearly disappear. In recent years, however, with the decline of both factories and coal power, the light-coloured moths have become dominant again.

Nowadays, evolution by natural selection is being observed in "the wild" among sticklebacks in British Columbia coastal lakes, among fruit flies in South America, and also in laboratories, on an hourly basis, around the world.

In his Pulitzer Prize–winning The Beak of the Finch: A Story of Evolution in Our Time, a 1994 book about the Grants and the significance of their work, author Jonathan Weiner sets out the paradox of the persistent hostility to Darwin's "theory". Evolution denial is a common habit of some of Darwin's most privileged beneficiaries in the United States, almost always evangelical Protestants, whose wealth often depends solely upon Darwin being right.

The paradox occurs in an especially bizarre way in the American South, in the "cotton belt", where the health of the cotton crop and the wealth that derives from it depend completely upon the application of Darwinian principles in the laboratory. It is only by the close observation of evolution by natural selection occurring in various cotton blights and pests that science has managed to devise at least temporarily effective pesticides and herbicides.

The paradox deepens in the recurring failure of those blight and pest remedies. There are now moths in Louisiana that can ruin cotton crops, and they're now 200 times more resistant to pesticides than they were before they first encountered them. Reject Darwin and you'll never understand why that happens. You'll continue to employ pesticides, and you'll find yourself in a losing battle, precisely because evolution happens.

It happens by natural selection. Resistant strains emerge by natural selection for certain heritable traits. Life is not static. Species are not fixed and unchanging. They evolve, and if Darwin were wrong, the branches of science known as immunology, bacteriology, and virology would never produce any results. It would all be quack science.

"There is no new theoretical structure that has come along since Darwin," Grant told me. "His ideas have been extended through genetics and have been modified and elaborated upon, but his ideas and observations and explanations have withstood the test of time."

And so Darwin prevails. Evolution is driven by hybridization and by sex selection, but the main engine is natural selection. It is how the earth ended up so rich in the diversity and abundance of life. It is evidence against the founding texts of all the world's great religions. It is evidence for life as a phenomenon that is constantly changing, constantly innovating, all on its own.

It is a rational explanation, subject to testable hypotheses. It is free for the asking and available to everyone, regardless of culture or class. It can account for everything from the virulence of diseases to the complexity of the human eye to the origin of humankind itself. No stirring elegy. No moving psalm.

Darwin prevails, more than anyone else. Charles Robert Darwin. Born 12 February 1809. Died 19 April 1882.

UBC's Beaty Biodiversity Museum will host Peter and Rosemary Grant, who will present their lecture Evolution of Darwin's Finches at 7:30 p.m. on Tuesday (November 20) in Room 100 of the Wesbrook Building (6174 University Boulevard). Admission is free.

Links: Rosemary Grant's page at Princeton

Peter Grant's page at Princeton

PBS Evolution Library - Finch Beak Data Sheet