What someone else wrote about the history of life on this planet.

Life on Earth began via amino acids (the building blocks of DNA) forming into prokaryotes, and for over 1.5 billion years they were the only life on Earth. From them evolved eukaryotes, multi-celled organisms, and much later true organisms.

Man evolved nearly 2 million years ago from a primate ancestor that also produced the apes - our genetic cousins. We share at least 96% DNA similarity with the Apes, as well as anatomy, physiology, form, and function. "Modern" man arose around 2 hundred thousand years ago, as many different strains, some of which died out, some were genetically subsumed, and others provided the genetic templates for what would become our modern strains such as Pacific Islander, Aborigine, African, Caucasian, Oriental, and what became Native American, crossing an ice/land bridge into Alaska from Asia.

-- Lord Bearclaw of Gryphon Woods