Three individuals left footprints in East Africa 3.7 million years ago. Walking upright on human feet, they had crossed a threshold in the long path of their evolution from vertebrates, mammals and primates to enter and dominate a new world. They were not alone. Others, related and descended in ways not entirely clear, spread out, flourished and disappeared; some became the people of today. Although we know a great deal of the story and new information is arriving ever more rapidly, there is still more to be learned about where, when and how our ancestors became us. We do know that we arrived not because we were inevitable, but by luck and happenstance along the way. And we know there were other kinds of humans who co-existed with each other and who might be here today but are not. Now updated and revised to reflect the latest findings and their implications, renowned anthropologist, author, and educator, William Howells draws together here the latest from all today's sciences to tell the fascinating stories of our evolution.