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 sonвЂ™s school warning of a potential lice outbreak in the classroom. Why and how did humankind become вЂњunusually successfulвЂќ? And what, to an evolutionary biologist, does вЂњsuccessвЂќ 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, itвЂ™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, weвЂ™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 didnвЂ™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.Дoes that apply to human beings, too? I once asked her, feeling like someone whining to Copernicus about why he couldnвЂ™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!Д«acteria 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 couldnвЂ™t help regarding conservationistsвЂ™ 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 MargulisвЂ™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.)

An extraordinary abundance of tinge