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Top 10 Mysteries of the First Humans

Humans are unique among life on this planet, and much remains a mystery as to how we evolved. What steps came first? Why did we evolve this way and not that direction? Why are we the only human species left? What other paths might we have gone down in our evolution? And what directions might we go from here?

- Charles Q. Choi, Special to LiveScience

Editor's Note: This is Part 1 in a 10-part LiveScience series on the origin, evolution and future of the human species and the mysteries that remain to be solved.