“The most impressive aspect of the living world is its diversity. No two individuals in sexually reproducing populations are the same, nor are any two populations, species, or higher taxa [categories of organisms]. Wherever one looks in nature, one finds uniqueness.” So wrote Ernst Mayr in This is Biology, published in 1997.
Part of his statement was a new idea to me. Clearly each species differs from the next. But I had not fully absorbed the notion that every organism, if it reproduces in pairs, is different from every other individual in its species. (Single-cell organisms like bacteria that divide into identical clones are the exception.) Every individual grass plant, every fish, every pure-bred dog, every ant is as different from another of its species as two human neighbors are. And, as Mayr adds, that makes uniqueness the order of the day.
But what about diversity and uniqueness in the non-biological, inanimate world? “Nature” includes not only living things but also rocks, water, air, light and other forces and materials. They seem to be unique in their own ways. Snowflakes are famously singular. Clouds change constantly. So does the surface of the ocean. Air flows and spins. I’m pretty sure I’ve never seen two rocks that are identical. It’s a good bet that every asteroid, planet and star is different from others. Looking out over the desert, the ocean, or the skies, we always witness diversity in shape, motion, color and light if we look closely enough.
Still, Mayr seems right that the diversity of living things “impresses” us in a distinct way. Each organism succeeds at being alive, yet does so in a slightly different way from the others.
Moreover, that booming variety, that hedge against species failure, comes on fast and strong. New life thrusts itself at us—in the new baby, in a puppy, among the trees springing up in corners of the yard, in the horde of ants and bees and birds of summer. In Origin of Species, Darwin wrote, “There is no exception to the rule that every organic being naturally increases at so high a rate, that if not destroyed, the earth would soon be covered by the progeny of a single pair.”
Diversity multiplied by fertility.