Diamond Speaks on Evolutionary Diversity

Jared M. Diamond '62-'65 delivered a lecture in a packed Sanders Theatre yesterday afternoon on the reasons why humans on different continents have had such different evolutionary histories.

"This is the most interesting, most important question of human history," Diamond said. "Finding the answer to this inherently simple question is difficult."

He cited the Indian subcontinents and New Guinea as being very diverse, each with thousands of different languages. In contrast, in places like tropical southeast Asia, people speak very similar languages and look very similar as well, he said.

Diamond, author of the Pulitzer Prize-winning Guns, Germs, and Steel: The Fates of Human Societies, said the human population has homogenized because of changes in lifestyle that he called "agricultural expansion."

He noted that originally, many cultures were primarily hunter-gatherers who were mobile and would shift their camps according to the changing seasons and food supply.

Populations settled down, he said, when they were able to live in villages where they had their own continual food supply through farming. This caused large groups to stay in the same places for long periods of time. Because they did not migrate, the groups did not diversify.

Diamond said the main factor behind the evolution of different regions at different rates was the domestication of various animals and crops.

Diamond explained the differences in evolution on different continents in terms of their geography. He said that because the continents were stretched out on different axes, migration was different on each one.

"This orientation of the axes has had a huge effect on human history," he said. "The result is that crops and livestock domesticated in one part of Eurasia quickly spread to the rest of that continent."

Diamond said the reason for this phenomenon is that Eurasia stretches 10,000 miles from east to west, whereas the Americas stretch 10,000 miles from north to south.

He said that in Eurasia, migration of domesticated animals and crops was easy because the climate and conditions are relatively the same across most of the continent. The Americas, by contrast, have dramatically different climates from north to south, making migration, and thus diversification, difficult.

The contrast is even more striking in Africa, Diamond said. In the fertile crescent, in the area of the Persian Gulf, cultivation was always easy and fruitful. In the warmer climates in the rest of Africa, such agriculture was impossible, thus preventing the spread of culture and people since those who were successful in agriculture stayed put for the most part.

Diamond said many people have tried to explain this diversification phenomenon in racial terms, saying that Africans were simply lazier than Europeans and did not have the energy to migrate. His discoveries have shed new light on this situation, though, showing those ideas to be incorrect.

Still, Diamond does not see his findings as entirely conclusive.

"I see this as an opening of a research program rather than a closing point. There are lots of questions to be answered in this area," he said, "I'm optimistic that we can come up with explanations for these broad patterns of human history."

Diamond's lecture was the second Roger Tory Peterson memorial lecture. The lecture, created in 1996 by the Harvard Museum of Natural History, honors Peterson, author of the Peterson Field Guides and a world famous ornithologist and author.

The first of these lectures was given in 1997 by Edward O. Wilson, honorary curator of entymology in the Museum of Comparative Zoology at Harvard and Pellegrino University research professor.

Wilson, who introduced Diamond yesterday, spoke about his experience with Peterson.

"We've begun in these lectures what I think will be a permanent institution at Harvard: to honor Roger Tory Peterson," Wilson said.