Jared Diamond may be the world’s best-known geography teacher. The UCLA professor bristles with academic credentials — he’s won a MacArthur Foundation "genius" grant and a National Medal of Science, among many other prizes.

But Diamond’s reach far exceeds the boundaries of academe. How did someone trained as a physiologist become a literary superstar?

Diamond’s breakout book, 1997’s "Guns, Germs and Steel: The Fates of Human Societies," won the Pulitzer Prize for its analysis of why Europeans and Asians came to dominate the world. "Collapse: How Societies Choose to Fail or Succeed," from 2005, analyzed the reasons successful civilizations vanish from the earth.

In a recent interview, Diamond talked about how he became one of the English-speaking world’s great explainers in arenas most of us don’t have the wherewithal to enter — physiology, anthropology, sociology, history. And he touched on several topics in his new book, "The World Until Yesterday: What Can We Learn From Traditional Societies?" (Viking, $36).

Diamond uses his years of experience in studying traditional peoples (especially in New Guinea, where he has worked for many years as a conservationist) to consider a compelling topic: What’s gotten better as man has become more civilized? What’s become worse? He examines human behavior in the areas of peace and war, treatment of the young and old, responses to danger, religion and diet in search of answers to a central question: What can we learn from people who live pretty much as humans did thousands of years ago?

Question: Are your three books "Guns, Germs and Steel," "Collapse" and now "The World Until Yesterday" a trilogy of sorts?

Answer: No, not a trilogy. Each of the books has been on what I found most fascinating at the time.

Q: Here’s a softball question: Why do you think your books have become so popular?

A: The subjects that fascinate me fascinate other people. Why is it that Europeans ended up dominating the world? What are the risks to our societies?

I’ve learned to write so as to explain things to myself. In my childhood I was always having to explain things to my sister (Diamond was 1 1/2 years older than his next oldest sibling). Now I explain things to other people. Part of it is that my books are about things I’m trying to understand myself. Much of the material in the book is not about my immediate specialty. I’ve had to explain it to myself, then explain it to other people.

Q: Your book looks at traditional vs. modern societies in several arenas. One is justice and how it’s meted out. You use as an example the way two groups of New Guineans negotiated after the death of a child in an auto accident. Both the driver and his company, and the child’s family, were able to resolve their feelings. What is your biggest take-away on this subject?

A: There are two take-aways. In our state justice systems, administered by a state government, we’re gaining some things. But we’re losing the emotional clearance in cases of divorce, disputes between brothers and sisters about inheritance, disputes between business colleagues.

The state justice system is not concerned at all about emotional clearance for the parties. That’s something that needs to be worked on. Among my close acquaintances, brothers and sisters (in a dispute) hired a mediator. It really made a difference. I have a school classmate whose sister was killed by robbers. The robbers were arrested and sent to jail, but 50 years later that still gnaws at my friend. That’s something state justice doesn’t do, and restorative justice attempts.

Q: You point to several differences between traditional warfare and modern warfare. Though many more people are killed in modern warfare, a greater percentage of a given population dies in traditional warfare. Has man’s urge to wage war changed much?

A: There is hope for optimism. It’s not that our propensity (for violence) has changed, but the reality is that fewer and fewer people are dying in wars than in the past. It may sound obscenely bad to say that, given Auschwitz, given Hiroshima. But when you look at the numbers, even in the worst affected countries, a considerably smaller percentage of people have died in war-related injuries.

Q: In your chapter about childhood, you note that in traditional societies, kids of multiple ages mix more with each other (a la the Little Red Schoolhouse); in our modern systems, kids are grouped according to age. What do you think is lost when kids are sequestered by age?

A: In traditional societies, all sorts of role models are available to children. Every adult in the village is an aunt or uncle. When kids who have misfortunes with their own parents have problems, they can learn from them, even if their parents were screwed up.

When I grew up in a suburb of Boston, we ran together on the street and played together in mixed groups. In my own home in a suburb of Los Angeles, there isn’t even a sidewalk. (Kids) can’t walk over to see friends; they have to see friends by appointment.

Q: You talk about "constructive paranoia" among traditional people — how they learn from on-the-ground experience to avoid danger. What have you as a person with a foot in both worlds learned from that trait?

A: I can say something that all my readers over 60 should think about. What are the real dangers in life? If you ask, people are likely to talk about nuclear power, terrorists, radiation. What you should really worry about is slipping in the shower and slipping on the sidewalk.

Q: You cite the Christian doctrine of forgiveness as one reason that Christianity has achieved enduring success. Explain.

A: The doctrine of forgiveness is often misunderstood to mean turn the other cheek. It’s more sophisticated than that ... the best way to resolve the dispute is not to jump to the nuclear option. The best way is to try to seek understanding, is forgive the person and try to reestablish the relationship.

Q: Your chapter on diet and noncommunicable diseases in emerging societies was frightening, especially in reference to diabetes. Talk about where you think that is going.

A: The incidence is rising. In particular, it’s rising most rapidly in countries that have been underdeveloped and poor and are becoming rich. For example, the rich Arab countries. The steepest rise is in diabetes — for people in places like Kuwait it’s 15 percent to 20 percent and higher (for Type 2 diabetes). They are wealthy, they can afford rich food and they haven’t learned the public-health lessons we have in the United States. In the U.S., rich people are slimmer than poor people. In India and Saudi Arabia, rich people are fatter.