Human Biology and Evolution Humans are Alive The earliest human life form can be traced back more than 3.5 billion years ago. Humans are said to be descendants of a single celled ancestor. Although they are different in size and shape all basic functions are alike. The more complex the organization of the cell became the more successful and developed it became. As these single celled organisms developed they became known as pre-humans. We share many …showed first 75 words of 1379 total…

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