Our subject, introduced last week, is a special section in the 100th anniversary issue of Natural History magazine (December 2000/January 2001), in which some of the best minds in the scientific establishment reflect on what it means to be human. The first essay in the section, "Threescore and Ten," is by Jared Diamond, who was interviewed last year in Books & Culture. Diamond begins with an anecdote from his fieldwork in New Guinea, recalling the "terror" of his New Guinean companions when, on a trip there in 1966, he made camp near a large tree. This fear struck him as irrational at first, but later he learned that "falling trees rank as a major hazard of life in the jungle: while you may see a tree fall only a couple of times a decade, if you're hoping to last seventy years but are not careful, you may end up crushed under a falling trunk or branch before having lived out your allotted time."

This kind of learning, Diamond observes, "derives from a trait distinguishing us humans from other animals: our unusually large capacity to modify our behavior in response to acquired information rather than relying solely on instinct." This is spectacularly evident in the use we make of information stored in writing. But this trait, Diamond further suggests, is nevertheless not as fully developed as we like to suppose, and here he states the gist of his argument:

Contrary to assumptions cherished by modern literate societies, I suspect we still learn best in the way we did during most of our evolutionary history—not by reading but through direct experience. Some limitations on our thinking skills, I believe, stem from our evolutionary history. And although these limitations are not insuperable, we do need to be more aware of them ...