Jared Diamond, a UCLA physiology professor and member of the Harvard Class of 1958, will give the Roger Tory Peterson Memorial Lecture this Sunday.

Why did European societies dominate and conquer those in Africa, the Americas, and Australia?

Why didn't Mexico's Aztecs or Peru's Incas expand across the Atlantic and conquer Spain, instead of vice versa?

Why, in case after case, were European colonizers victorious over local peoples?

Those questions have dogged researchers for centuries, sometimes leading to racist "genetic superiority" or "master race" answers.

But the answer may have been outside, not inside, the Europeans.

Jared Diamond, a UCLA physiology professor and member of the Harvard Class of 1958, says the answer lies in the Eurasian environment, particularly in the Middle East's Fertile Crescent, where farming was first developed thousands of years ago.

Diamond, who will deliver the 1999 Roger Tory Peterson Memorial Lecture on Sunday, May 9, in Sanders Theatre, believes that the mix of plants and animals in that region gave Europeans a head start over people in other parts of the world.

Those plants and animals were useful in a variety of ways, from providing better nutrition to acting as beasts of burden and vehicles of war, he says. Their presence provided an incentive for people to take up farming, which led to increased population, more complex political structures, standing armies, and the ability for some to pursue technological innovations instead of food gathering.

The close-packed cities also allowed diseases -- some of which initially mutated from domestic animals -- to take hold and then to devastate native peoples elsewhere who lacked the Europeans' hard-won immunities, Diamond says.

Diamond presented his theories in his 1998 Pulitzer Prize- winning book, Guns, Germs and Steel: The Fates of Human Societies. He will discuss the subject Sunday during the Peterson Lecture, sponsored by the Harvard Museum of Natural History.

Diamond said in a phone interview that a close link exists between his work and the work of Roger Tory Peterson, the world-renowned ornithologist, author, and artist in whose memory the lecture series was founded in 1997.

Diamond said many insights into human evolution were gained through studying bird evolution. Both are driven by competition, he said, with human societies evolving through competition with other human societies.

Joshua Basseches, the Natural History Museum's executive director, said Diamond explains complex scientific subjects in a way that the general public can understand.

"He's phenomenally interesting and a wonderful speaker," Basseches said.

The lecture, which begins at 4 p.m., is free and open to the public. The series, which began in 1997 but which did not occur last year, is expected to become an annual event.

Diamond, who attended Harvard from 1954 to 1958 and who was a junior fellow in Harvard's Society of Fellows from 1962 to 1968, said the trip will bring back some memories. He attended his first lecture as a Harvard student in Sanders Theatre.

The idea for Guns, Germs and Steel came while Diamond was doing fieldwork in New Guinea, where some of the local people still used stone tools. Diamond said he realized soon after his arrival in 1964 that though the local people were still using primitive implements, it wasn't because they were less intelligent or less able to learn than Europeans.

That set him on the path to find out why.

"I thought they were working with stone tools because they were primitive people. It took me about one day to realize they're not primitive people at all," Diamond said. "The question [of why they're still using stone tools] came up on the first day. The answer took 30 years to find out."

-- The Roger Tory Peterson Memorial Lecture takes place Sunday, May 9, 4 p.m., at Sanders Theatre. Doors open at 3:30 p.m. The event is free and open to the public. Space is limited. Call the Sanders Theatre Box Office at (617) 496-2222 for reservations.