It was decades before the scientific community accepted natural selection. One of the theory's major weaknesses was an inability to explain how heredity works. Darwin didn't know about genes or mutations, let alone the astonishing fact that humans share almost 99 per cent of their genetic makeup with chimpanzees and 85 per cent with mice.
Still, Mr. Quammen writes, the centennial of The Origin of Species was celebrated in the scientific community in the confidence that Darwin had got it right, and since then far more evidence has piled up.
But gaining broad acceptance for evolution by natural selection has been more difficult. Brian Alters, founder and director of the Evolution Education Research Centre at McGill University in Montreal, suspects that Darwin would be surprised to know that the campaign continues so long after his death.
"Darwin, to this day, is anathema to millions and millions of North Americans," says Dr. Alters, an expert on science education who appeared as an expert witness in a high-profile 2005 case over whether intelligent design - a modern form of creationism - should be taught in Pennsylvania public schools. "He is almost right up there with Hitler. He symbolizes atheism. He's the guy who removed God out of creation."
Now an agnostic, Dr. Alters is a former creationist who was born into a fundamentalist Christian household in California and learned about evolution only as a teenager.
It was like taking a long, cold shower, he says. "The creation story is a beautiful story. There is a heavenly father who created all things. He didn't want the man to be alone, so created woman. He created animals. There is this beautiful Garden of Eden the creator wanted for these special humans.
"Then, all of a sudden, in a public-school science classroom, you hear it is a whole other thing called natural selection. It is a story mainly about death, and extinction and horrible suffering, and a lot of chance involved. If you reran the tape, maybe humans wouldn't even have evolved."
But many religions, including Roman Catholicism, are not opposed to evolution, Dr. Alters says. So why do so many people remain unconvinced? A survey of Canadians conducted in 2007 by Angus Reid found that 22 per cent of respondents believe that God created humans in their present form while an additional 19 per cent said they just aren't sure about evolution.
A combination of scientific illiteracy and religious illiteracy comes in to play, Dr. Alters says. Many people don't know that they can believe in both God and evolution, he says.
"Rarely do they ever hear they can have their cake and eat it too. The supreme being, let's say God, is capable of using evolution to bring humankind and all organisms about. Evolution does not mean atheism or agnosticism."
The widespread skepticism, he adds, also stems from the fact that evolution challenges something many people cherish: the notion that humans are special - and superior to other animals.
In his book, Mr. Quammen argues that this is where Darwin ran afoul of Christianity, Judaism, Islam and probably most other religions on the planet. Evolution refutes "the supposed godliness of man - the conviction that we, above all life forms, are spiritually elevated, divinely favoured, possessed of an immaterial and immortal essence, such that we have special prospects for eternity, special status in the expectations of God, special rights and responsibilities on Earth."
Teachers sometimes hesitate to bring up evolution in class, Dr. Alters says, because they don't want to upset students or their parents. Some don't use the word evolution, or will talk about it only with respect to animals, not humans.
"A teacher will start teaching evolution and immediately a tear rolls down a student's face. We get reports of this all the time," he says. "Just because we win in court with logic and science doesn't mean we win the hearts and minds of people outside of the courts."
THE DARWIN ADMIRER: BY GRADE 2, HE KNEW WHAT HE WANTED TO DO
The table where the phylum feasters will sit down to dinner in Bishops Mills is still piled high with the shells of the mussels, clams and snails that Fred Schueler is currently studying. It will all be cleared away in time for the party, his wife says.
Guests will be offered a tour of the natural history centre, which is housed in an old general store and described by Dr. Schueler as a private, "mom and pop research institute" supported by long-time friends who consider its work important. The elk toes, elephant ears and other freshwater mussels it contains are part of the fourth-largest such collection in Canada.
Dr. Schueler's life really has been influenced by Darwin. He, too, undertook his voyages of exploration - including a coast-to-coast trip doing field work for an illustrated natural history of Canada - as a young man. He now studies what effect new arrivals, such as zebra mussels, have on native animals and plants, and says Darwin invented the concept of an alien species.