07 February 2001 | Why did human history take such a different evolutionary course over the last 13,000 years? Why did peoples of Europe and eastern Asia spread to dominate the globe, while African Americans, Native Americans and Aboriginal Australians were decimated, subjugated or exterminated by European colonialists?

"Those differing rates of expansion on different continents are the biggest unsolved problem of history," said well-known biologist and Pulitzer Prize-winning author Jared Diamond, who spoke recently to an overflow audience of students, faculty and community guests as part of the Berkeley Museum of Paleontology's program of public lectures. "It seems to me that they are attributable to differences in continental environments, not to biological differences."

Jared, author of the 1998 Pulitzer Prize for "Guns, Germs and Steel: The Fates of Human Societies," has brought history and biology together in his new theories of human development, presenting a global account of the rise of civilization. In doing that, the UCLA professor of physiology, educated at Harvard, proposes a new perspective on race-based theories of human history.

The story, which began around A.D. 1500 - the approximate time when some Iron Age states and empires of Eurasia and North Africa were on the verge of industrialization - deserves updating, he said, thanks to recent advances in a variety of fields, including molecular biology, plant and animal genetics and biogeography, archaeology and linguistics.

In one part of the world, two Native American peoples - the Incas and Aztecs - were just starting to experiment with bronze. Meanwhile, parts of sub-Saharan Africa were divided among small indigenous Iron Age states or chiefdoms. But all peoples of Australia, New Guinea and the Pacific islands, and many peoples of the Americas and sub-Saharan Africa, were still living as farmers or hunters and gatherers with stone tools.

"Those differences were the cause of the modern world's inequalities," Diamond asserted. "Historical accounts fail to explain the spread of human populations adequately. Many people, or even most people, assume that the answer involves biological differences in average IQ among the world's populations, despite the fact that there is no evidence for that belief."

Diamond, also author of "The Third Chimpanzee" (1992), contends, like many scholars, that the rise of weapons technology and the domestication of animals, namely horses, accounts for part of Europe's conquest of the New World. But the spread of "nasty germs," those contracted from human contact with domesticated animals, also brought down New World populations.

"Recent studies of microbes, by molecular biologists, have shown that most human epidemic diseases evolved from similar epidemic diseases of the dense populations of Old World domestic animals with which we came into close contact," he said.

"Measles and tuberculosis, for example, evolved from diseases of our cattle, influenza from a disease of pigs, and small pox possibly from a disease of camels," he said. "The Americas had very few native domesticated animal species from which humans could acquire such diseases."

Eurasia ended up with the most domesticated animal species, in part because it's the world's largest land mass and offered the most species to begin with. But the Americas also harbored more than a thousand native wild mammal species 13,000 years ago and seemingly offered just as much material for domestication.