Science now takes for granted the importance of forces and time spans we can’t perceive directly
Slipping the Bonds
Despite his misstep with the Weald, Darwin was profoundly influenced by his training in geology and his deep friendships with many of the leading geologists of his time. Natural selection, in effect, was a force directly analogous to erosion and deposition. Like erosion, it was capable of destruction, eliminating the less fit in the struggle for existence. And, like sedimentation, natural selection could also act as a creative force, building new forms through the slow accretion of imperceptible changes.
But if geology was slow, natural selection was even slower. Lyell, in a metaphor that Darwin later admired as “capital,” made the point in his book Principles of Geology:
In a word, the movement of the inorganic world is obvious and palpable, and might be likened to the minute-hand of a clock, the progress of which can be seen and heard, whereas the fluctuations of the living creation are nearly invisible, and resemble the motion of the hour-hand of the time-piece.
Natural selection needed time, and lots of it—time immeasurable in human life spans.
Aware of the challenge involved in communicating such a vast expanse of time, Darwin began the Origin in a beautifully calculating way. The first chapter is a compendium of examples of artificial selection brought about over a few generations of selective breeding. These reassuring instances demonstrate selection at the human scale, with human agency as the driving force. Many of Darwin’s readers, country gentlemen of means, would have been intimately familiar with the breeds he discussed. An avid pigeon fancier himself (he boasted of belonging to two London pigeon clubs), Darwin marshalled the English carrier and the short-faced tumbler, the runt and the barb, the turbit, the pouter and the fantail—all the while alluding to the power of pigeon fanciers to generate these breeds from a single rock-pigeon ancestor. Easing slowly into the scope of time, Darwin reassured his readers that these many breeds had been brought about in the course of human history.
This first chapter, “Variation under Domestication,” had, as its name suggests, an explicit agenda. In it, Darwin established the importance and ubiquity of variation. By emphasizing the consequences of artificial selection, he struck an important first blow against the purported immutability of species. And by alluding to the common ancestry of so many radically different contemporary variations, he set the cornerstone of the argument for descent with modification. But behind these explicit goals, this chapter also bolstered readers’ confidence in their ability to understand vast stretches of time and to apprehend nature through their senses. Darwin wrote, for example, that:
the earliest known record of pigeons is in the fifth Ægyptian dynasty, about 3000 B.C. … but Mr. Birch informs me that pigeons are given in a bill of fare in the previous dynasty.
He thus anchored his argument in the realm of human history. When he spoke of how “King Charles’s spaniel has been unconsciously modified to a large extent since the time of that monarch,” he reassured his readers that the forces at play are within the scope of human experience. He knew, I believe, that if we could understand his examples—which he explained with extraordinary care—then we might be ready for a glimpse of deep time.
By offering that glimpse, the Origin ushers us into the world of contemporary science. It asks us to acknowledge the riotous diversity of living forms and then accept that they are the result of material forces we cannot directly observe, acting over time spans we cannot imagine. It reminds us that chance operates at scales both large and small, and that selection sifts inexorably through life’s variety. We live our lives in three dimensions for our threescore and ten allotted years. Yet every branch of contemporary science, from statistics to cosmology, alludes to processes that operate on scales outside of human experience: the millisecond and the nanometer, the eon and the light-year. For some, this is cause, if not for despair, then for strong suspicion and perhaps even rejection of the scientific enterprise. But there is grandeur in the notion that we are part of nature, and not above it. And there is comfort in the realization that, although our senses and brains constrain us, we can still understand phenomena far beyond those we can witness. In the end, it may be this ability to slip the bonds of our own experience—those of time, those of our senses—that makes us human.
So it’s worth taking a moment to contemplate what we now know: The Earth is 4,540,000,000 years old. Life has been around for at least 3,500,000,000 of those years.
- Darwin, C. 1868. The Variation of Animals and Plants Under Domestication. New York: Orange Judd and Company.
- Hallam, A. 1989. Great Geological Controversies, second edition. New York: Oxford University Press.
- McPhee, J. 1981. Basin and Range. New York: Farrar, Strauss and Giroux.