We came back with fewer people than we left with

Five of us went down to the river for water. We got the water. — Forager, about 50,000 BC

In a South African cave called Swartkrans, there's a child's skull with two holes in it. They line up with the fangs of a leopard found in the same layer. Higher up, in layers about a million years old, there's burnt bone from fires somebody kept going at the mouth of the cave, over and over. Bob Brain, the scientist who dug there, figured the fires were to keep the leopards out. The cave had changed hands. Took a while, but it did.

For now: if a mountain lion approaches, don't run. Look big; fight back if attacked.

The full file

Brain's work turned the old story over. Raymond Dart had looked at bones from South African caves and decided our ancestors were killers swinging bone clubs. Brain's 1981 book, The Hunters or the Hunted?, showed the bones were mostly what the predators left after eating us. We were lunch.

The fire he tested himself. In 1985 he burned local wood in campfires right there at Swartkrans and heated bones in a kiln to compare. In 1988 he and Andrew Sillen called the burnt bones there the earliest direct evidence of our ancestors using fire, somewhere between 1 and 1.5 million years ago.

The advice hasn't changed much. If a mountain lion comes toward you, don't crouch or bend over. It makes you look like something to eat. Pick the children up without bending down. Some lessons you only have to learn once.