Did a series of ice ages speed up human evolution?
Humans, chimps and gorillas are all descended from one common ancestor - an east African proto-ape - who lived four million years ago. But what caused this evolutionary split into three different species? Startling new research suggests the answer comes from the succession of dramatic climate changes that drove some members of the species out of the trees and on to the plains, where they developed human characteristics.
In a fascinating introduction to this phenomenon, John and Mary Gribbin explain the various theories surrounding ice ages, from the calculation of astronomical rhythms and the Earth's changing orbit, to the hidden record of ice epochs and interglacials held in the ocean floor.