My father was ill that morning, so my mother set out alone in the Land Rover, accompanied by her two Dalmatians. She spent the morning crawling along the slope of the nearby gorge but found very little until just before noon, when she noticed a scrap of enormously thick bone protruding from beneath the surface. She instantly realized that it was part of a hominid skull—and that two teeth were embedded in the rock just above it. Elated, she dro...