humanus corporis, the body louse, must not be especially old, because its need for clothing meant that it could not have existed while humans went naked. humanus capitis, the head louse, could be an ancient annoyance, because human beings have always had hair for it to infest. It occurred to him that the two louse subspecies could be used as an evolutionary probe. In fact, Stoneking learned, body lice are so dependent on the protection of clothing that they cannot survive more than a few hours away from it. humanus corporis-body lice, which feed on skin but live in clothing.

humanus capitis-head lice, which feed and live on the scalp-and P. The most common louse found on human bodies, he discovered, is Pediculus humanus. As a biologist, it was natural for him to noodle around for information about them. Stoneking is a researcher at the Max Planck Institute for Evolutionary Biology in Leipzig, Germany. One way to begin answering them came to Mark Stoneking in 1999, when he received a notice from his son’s school warning of a potential lice outbreak in the classroom. Why and how did humankind become “unusually successful”? And what, to an evolutionary biologist, does “success” mean, if self-destruction is part of the definition? Does that self-destruction include the rest of the biosphere? What are human beings in the grand scheme of things anyway, and where are we headed? What is human nature, if there is such a thing, and how did we acquire it? What does that nature portend for our interactions with the environment? With 7 billion of us crowding the planet, it’s hard to imagine more vital questions.

Seeing my face brighten, she added: Of course, the fate of every successful species is to wipe itself out. For one thing, she said, we’re unusually successful. But as I recall it, she answered that Homo sapiens actually might be interesting-for a mammal, anyway. This was just chitchat on the street, so I didn’t write anything down. Compared to this power and diversity, Margulis liked to tell me, pandas and polar bears were biological epiphenomena-interesting and fun, perhaps, but not actually significant.ĭoes that apply to human beings, too? I once asked her, feeling like someone whining to Copernicus about why he couldn’t move the earth a little closer to the center of the universe. Microorganisms have changed the face of the earth, crumbling stone and even giving rise to the oxygen we breathe. Heck, the number of bacterial cells in our body is ten times more than the number of human cells!īacteria and protists can do things undreamed of by clumsy mammals like us: form giant supercolonies, reproduce either asexually or by swapping genes with others, routinely incorporate DNA from entirely unrelated species, merge into symbiotic beings-the list is as endless as it is amazing. More than 90 percent of the living matter on earth consists of microorganisms and viruses, she liked to point out. Still, she couldn’t help regarding conservationists’ preoccupation with the fate of birds, mammals, and plants as evidence of their ignorance about the greatest source of evolutionary creativity: the microworld of bacteria, fungi, and protists. Margulis was no apologist for unthinking destruction. Hey, Charles, she would call out, are you still all worked up about protecting endangered species? She knew I was interested in ecology, and she liked to needle me. Until Margulis’s death last year, she lived in my town, and I would bump into her on the street from time to time. A researcher who specialized in cells and microorganisms, Margulis was one of the most important biologists in the last half century-she literally helped to reorder the tree of life, convincing her colleagues that it did not consist of two kingdoms (plants and animals), but five or even six (plants, animals, fungi, protists, and two types of bacteria). THE PROBLEM WITH environmentalists, Lynn Margulis used to say, is that they think conservation has something to do with biological reality. (This essay was a finalist for a 2013 National Magazine Award in the Essay category.)

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