Science: The Oldest Man?

When the young anthropology assistant burst into the campsite in Ethiopia's remote Awash Valley, he was so excited that he could hardly gasp out the news. Only five minutes' walk from the tents, he had just spotted a completely intact human-like jawbone sticking out from under a layer of volcanic rock on the shore of a dry lake. Alemayehu Asfaw figured that the fossil was at least as old as the rock—and the rock had already been dated as more than 3 million years old.

The American leader of the expedition, Anthropologist Carl Johanson of Cleveland's Case Western Reserve University, rushed to...