“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.
This was, to an extent, a new idea to me. Clearly each species is different from the next. But I had not fully absorbed the notion that every single organism, if it reproduces in pairs, is different from every other in its species. Every individual grass plant, every tree, every insect, every ant is as different from the one next to it as two human beings are. Why? As Mayr explains, diversity ensures that some individuals will fit the environment; as the environment weeds out some versions, others will survive.
But what about the diversity in the non-biological, inanimate world? “Nature” includes not only living things but also rocks, water, air, light and other forces and materials. Aren’t they unique in their own ways? Snowflakes are famously singular. Clouds are constantly changing. So is 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 the others in some ways. Looking out over the dessert, the ocean, or the skies, we certainly see diversity in shape, motion, color and light.
Still, I think the diversity of living things does “impress” us, as Mayr wrote, in a distinct way. The variety of the organisms in a species is more individualistic, unique, than the motions, colors and contours of the elements around us. And it captures our attention partly because of the sheer power of fertility. New life is always thrusting itself in front of us—in a sister’s baby, in a new puppy, among the trees at the back of the backyard, in the horde of ants and bees and birds of spring. 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 is the music, but fertility is the amplifier. It’s the combination that gets our attention. And we are not remote observers. We are both notes in the music and members of the orchestra.