We walk this earth--we, this unparalleled experiment in evolution--reflexively assuming we are the crown of creation. Certainly we are rare and strange: As biological anthropologist Owen Lovejoy of Kent State University says, "The chances that a creature like us will ever happen again are so small that I can't even measure them."

But that ascent-of-man picture is looking as dated as the flat earth. A series of scientific and technological breakthroughs have altered much of our fundamental understanding of human evolution. In the new view, the path to Homo sapiens was amazingly dilatory and indirect. Along the way, our planet witnessed many variations on the human form, multiple migrations out of Africa, interspecies trysts, and extinctions that ultimately wiped out all hominid species except one (pdf). "Human evolution used to seem simple and linear," says paleoanthropologist William Jungers of the State University of New York at Stony Brook. "Now, you look at almost any time slice and you see diversity. We may be special and we may be lucky, but we're far from the only human experiment."