Kevin Sites in the Hot Zone - Chapter 15: Coming HomeIn this final chapter of "A World of Conflict," Kevin Sites returns home to the U.S., only to confirm what he suspected -- that in the year that he was gone little had changed.

Kevin Sites in the Hot Zone - Chapter 14: Israel-Hezbollah WarThe war between Israel and Hezbollah shook the landscape in the Middle East.

Kevin Sites in the Hot Zone - Chapter 13: Sri LankaKevin Sites covered Sri Lanka as violence erupted between the government and Tamil Tiger rebels, pushing a nation with so much to lose back to the brink of all-out war. In rebel-held territory Sites interviewed Tiger fighters about their tactics and reported on the many effects of war still seen in the region.

Kevin Sites in the Hot Zone - Chapter 12: Nepal and KashmirKevin Sites covered Nepal during a time of sweeping political change that followed mass nationwide protests, forcing the autocratic King to cede power.

Kevin Sites in the Hot Zone - Chapter 11: Child BrideIn Afghanistan, Kevin Sites met a 12-year-old girl named Gulsoma, whose incredible story of resilience resonated with millions of people worldwide. She was only six years old when she was sold to a neighbor family in Kandahar as a child bride.

Kevin Sites in the Hot Zone - Chapter 10: AfghanistanReporting from Afghanistan in spring 2006, more than four years after the U.S.-led coalition ousted the Taliban, Kevin Sites found that war is not over in the country.

Kevin Sites in the Hot Zone - Chapter Nine: ChechnyaIn Chechnya during the winter of 2005-2006, Kevin Sites reported on a region still reeling from lingering conflict between Russia and Islamic separatists. The conflict engulfed Chechnya in the 1990s, and even now, half of the population is yet to return. Those that have eke out a living amid the rubble.

Kevin Sites in the Hot Zone - Chapter Eight: Iran

Kevin Sites in the Hot Zone - Chapter Seven: IsraelIn Israel, Kevin Sites interviewed Kinneret Boosany, a victim of a suicide bombing at a Tel Aviv cafe in 2002.

What do you get when you cross scholarly research and dick jokes? Nothing to laugh at, normally. But science writer Jim Holt defies the Heisenberg principle of humor — you can't study it without killing it — in his book Stop Me If You've Heard This: A History and Philosophy of Jokes. We caught up with him walking into a bar.

Wired: One question you tackle is who invented the joke. Weren't we cracking wise back in the caves?

Holt: No, the classic joke form — setup with incongruity, punch line that resolves the incongruity —seems to have come out of Greece and Rome. There's this guy in Greek -mythology called Palamedes who invented practically everything — numbers, currency, lighthouses, breakfast, lunch, and dinner. He also supposedly invented the joke. And, of course, he was stoned to death.

Wired: So where do new jokes come from?

Holt: It used to be that all the jokes I got came from Wall Street. Now, with the Internet, they're sort of everywhere and nowhere at once. But the ideas for jokes are cultural — concepts that keep reappearing in different guises over the centuries.

Wired: There are lots of theories about why we joke. Which do you find most plausible?

Holt: Well, there's the superiority theory, that jokes express scorn for your inferiors — cripples and cuckolds and foreigners and the like. Plato said we laugh at vice. Then there's the Freudian interpretation, that it's all about sexual repression. Finally, there's the seduction theory, based on the observation that men do most of the joking while women do most of the laughing. Christopher Hitchens wrote a piece in Vanity Fair arguing that the only way most guys can impress women is to make them laugh.

Wired: But your favorite explanation is a mashup of Kant and evolutionary biology, right?

Holt: V. S. Ramachandran, the brain researcher, has a theory about the origin of laughter — that when you're in the jungle and there's an apparent threat, the first member of the kinship group to notice that it's not a real threat emits this stereotyped vocalization. And it's contagious, so everyone starts laughing. That's also the basis of the relief theory of humor, that there's a release of the energy you had summoned up to solve some puzzle. Kant said that the essence of humor is a strained expectation dissolving into nothing.

Wired: Did you find any candidates for the perfect joke?

Holt: I did find what might be the shortest possible joke: "Pretentious? Moi?"