For well over a century, ever since Charles Darwin, Western scientific thought has stated that all of today's species, including man, have arisen by the modification of earlier, simpler forms of life. This means that the story of human evolution begins with a creature that most of us today would not consider human.

Today's human beings, or Homo sapiens sapiens , belong to the Hominid family tree. Hominid means "human types" and describes early creatures that split off from the apes and took to walking upright, or on their hind legs. In the overall history of life on Earth, the human species is a very recent product of evolution. There are no human-like fossils older than 4 million years, which makes them only one-thousandth the age of life on Earth. The oldest and first ancestor of all known hominids was probably Australopithecus afarensis, named for a region in...