Shadows of Forgotten Ancestors

Darwin’s friends Huxley and Hooker prodded him to quit stalling and write the paper that would make an ironclad case for evolution. He complied and was nearing its completion in 1858, while Wallace, now in Indonesia and sick with malaria, tossed and turned, grappling with the question “Why do some die and some live?”²² Emerging from his stupor, he understood natural selection. He wrote “On the Tendency of Varieties to Depart Indefinitely from the Original Type” and promptly mailed it to Darwin, asking him to use his judgment about what should be done with it. Darwin was distressed to see how very close Wallace’s work was to his own writings of 1839 and 1842. In 1844 he had combined them into an essay, but it remained unpublished. Darwin turned to his friends for guidance on how to deal ethically with this dilemma. Hooker and Lyell came up with a wise solution: Present both the Wallace paper and a version of Darwin’s unpublished 1844 essay at the next meeting of the Linnaean Society and publish them together in the Society’s Proceedings.²³ Thereafter, Wallace always spoke of evolution as being Darwin’s theory and Darwin always credited Wallace with its independent discovery. Darwin now applied himself to the task of writing the book that would cause so much trouble.

On November 24, 1859, The Origin of Species was published. The first edition of 1,250 copies was snapped up by the booksellers. Darwin had been careful to make only one reference to humans in the whole book: “Light will be thrown on the origin of man and his history.”²⁴ Anything more from his pen on this delicate matter would have to wait another twelve years, for the publication of The Descent of Man. His restraint fooled no one. Given its formidable armamentarium of data, there could be no reconciling The Origin with a literal rendition of Genesis.

Chapter 4

A GOSPEL OF DIRT

I detest all systems that depreciate human

nature. If it be a delusion that there is

something in the constitution of man that is

venerable and worthy of its author, let me live

and die in that delusion, rather than have my

eyes opened to see my species in a humiliating

and disgusting light. Every good man feels his

indignation rise against those who disparage his

kindred or his country; why should it not rise

against those who disparage his kind?

THOMAS REID

letter of 1775¹

When I view all beings not as special creations,

but as the lineal descendants of some few

beings which lived long before the first bed of

the Cambrian [geological] system was

deposited, they seem to me to become

ennobled.

CHARLES DARWIN

The Origin of Species, Chapter XV²

Mankind has conducted an experiment of gigantic proportions,” Darwin wrote in The Origin of Species. He was struck by the success of “husbandry,” as it is tellingly called, in generating new varieties of animals and plants useful for humans. Nature provides the varieties and we select who shall reproduce, which traits we want preferentially to propagate into future generations. By transferring pollen from flower to flower with a camel’s hair brush, or by letting the stallion in with the mare, humans take it upon themselves to determine who shall mate with whom. Indigestible crops, weakling horses, scrawny turkeys, sheep with knotty coats, and cows that are grudging with their milk are discouraged from reproducing. Generation after generation, by cumulative selection, humans impress their interests on the heredity of the plants and animals whose breeding they control. But Nature, too, selects those plants and animals which by its lights happen to be more favorably adapted than their fellows; such fortunate beings preferentially reproduce, leave more offspring and, as time goes on, supplant the competition. Artificial selection helps us to understand how natural selection works.

The ability of the environment to nurture and sustain large populations—the so-called carrying capacity—is of course finite. As the number of organisms increases, not all will be able to survive. There will be a stringent competition for scarce resources. Slight differences in ability, imperceptible to a casual observer, may spell life or death to the organism. Natural selection is a great sieve, straining out the vast majority and permitting only a tiny vanguard to pass its heredity on to the next generation. Natural selection is far more ruthless than the most callous and resolute animal breeder in determining the genetic makeup of future generations. And instead of the measly few thousand years since the domestication of animals began in earnest, natural selection has been working for billions.