William Calvin

Hi John,

I've been visiting the distant cousins this summer—the very distant ones, the apes with whom we shared a common ancestor between 18 and 7 million years ago. While I'd prefer to visit them in the wild, in southeast Asia and central Africa, I had to settle for an intense dose of them at the San Diego Zoo's excellent habitats. I arranged for a behind-the-scenes visit with their keepers for a dozen scientists interested in human evolution, who wanted to know more about what ape behaviors were like.

Apes evolved from the monkeys about 25 million years ago; they lost their tails in favor of doubling brain size. The gibbons and siamangs are on a branch that dates back about 18 million years, and the orangs on the branch at about 12 million years. They are the acrobats of the apes, with shoulders far more versatile than monkeys. The siamangs and the orangs are housed together at the San Diego Zoo and it makes for a fascinating display of virtuosity. I made good use of my new telephoto lens, as you'll see when the book comes out next spring; the postcard pictures are of the siamang, an orang, and various bonobos.

The gorillas split off about 8-10 million years ago. They sure lost the acrobatic skills of their presumed ancestor with the orangs, perhaps because they specialized in a vegetarian niche of low quality food that requires a very long gut and big belly.

About 7 million years ago, we last shared a common ancestor with the chimps and bonobos. The hominids differed, initially, in losing the big canine teeth and in standing upright enough to rearrange the hips. They had a pint-sized brain like the other great apes; the tripling of brain size didn't even begin until the ice ages kicked in about 2-3 million years ago. If only more of those intermediate species had survived—both Neanderthals and, in China, Homo erectus went extinct recently, after our own lineage achieved structured thought, our capacity for long sentences and contingent planning.

Watching any of the four great ape species will, to an extent unmatched by the lesser apes and the monkeys, remind you of people that you know. The chimps and bonobos are considerably more social than gorillas (what with their harem structure that excludes most males) and the orangs (who, as adults in the wild, seldom see one another except for "conjugal visits"). Watching bonobos (essentially the oldest of the chimp subspecies, from the left bank of the Congo), you will see reassuring touches, the arm around the shoulder, kissing, and the grinning "play face."

This overlap with what we had supposed were exclusively human behaviors was one of the surprises of the last few decades of research. Judging from the chimps and bonobos, a lot was in place before the hominid branch split off at 7 million years ago, perhaps even the capacity for simple language (with years of tutoring, they can do about as well as two-year-old kids at understanding a sentence). They may lack structured thought, but so might our big-brained ancestors—at least, until about 50,000 years ago when sustained creativity first appears in the archaeological record. Before then, Homo sapiens wasn't doing much that was any different from the Neanderthals. Conservatism was the rule, not innovation, and the life of the mind was probably rather minimal.

That's why the great apes are so precious to us. Along with the stones and bones of archaeology, these distant cousins are the other small window into our own past. Take your binoculars, to watch those fleeting facial expressions, and try to match them up with people you know.

Cheers,

Bill