A brief history of Homo sapiens—and a prognosis for our survival:

“Microorganisms have changed the face of the earth, crumbling stone and even giving rise to the oxygen we breathe. 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.

“Does 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. Aren’t we specialat all?

“This was just chitchat on the street, so I didn’t write anything down. But as I recall it, she answered that Homo sapiens actually might be interesting—for a mammal, anyway. For one thing, she said, we’re unusually successful.

“Seeing my face brighten, she added: Of course, the fate of every successful species is to wipe itself out.”