For more than 50 years, historians have puzzled over the three-story stone ruin, which is attached to the ancient walls of the town of Jericho in what's now the West Bank.

Eleven thousand years ago Jericho residents had mastered neither agriculture nor the wheel and had only just abandoned a nomadic lifestyle. How could they have built what some see as the world's first monumental public building in one of the world's first cities?

"There is no doubt that the Tower of Jericho has befuddled people for a while," said archaeologist Brian Byrd, who wasn't part of the new study, published in the March issue of the journal Antiquity.

"It still remains a bit of an enigma."

New computer simulations suggest that