Do Men Without Mates Endanger the World?

July 19, 2004 -- The cruising scene isn't too hot in Abha, a small, southwestern Saudi town.

Bored young men stroll through the dusty town or drive down the sleek Abha-Gizan highway at breakneck speeds, according to travelers' accounts. And under the watchful eyes of the muttawa — the dreaded Saudi religious police — women, clad in enveloping, all-black abayas, shop unobtrusively in the marketplaces.

Abha is a fairly typical Saudi town.

But since the Sept. 11, 2001, attacks in the United States, Abha has held a particular fascination for many experts.

Situated in the remote southwestern province of Asir near the Yemen border, Abha — along with the neighboring town of Khamis Mushayt — was home to at least six of the 9/11 hijackers.

The local mosques, the resident imams, the remoteness of the mountainous province have all come under scrutiny in an attempt to uncover why the young men hijacked planes that fatal day and flew them kamikaze-fashion into U.S. buildings.

But as conflicts and terrorist attacks across the world continue to wreak a deadly toll, demographers have been looking at population patterns to see if they offer some explanation for human violence.

The 9/11 attacks refocused attention on a 1997 study by two Canadian psychologists arguing that societies with a high proportion of young males are more prone to violence.

Adding a new dimension to the study of the roots of violence, Neil Weiner and Christian Mesquida argued that societies with a high ratio of males aged between 15 and 29 are more likely to be aggressive and militaristic.

And earlier this year, a new study on gender and violence hit the stands — and sent ripples of anxiety in the international community.