The oldest stone tools found are dated from 2.7 - 2.9 million years ago. The species that made these tools is unknown.
13
Shark corneas are used in eye transplants and shark bone marrow can be used to graft human bones.
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An average heart beats 100,000 times a day, pumping some 2,000 gallons of blood through its chambers. Over a 70-year life span, that adds up to more than 2.5 billion heartbeats.
73
Women have about four times as many foot problems as men; lifelong patterns of wearing high heels often are the culprit.
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Modern humans first appeared about 200,000 years ago, but record keeping didn't begin until about 6,000 years ago. That means about 97% of human history is lost.
21
Blue eyes are a genetic mutation. Before the mutation occured, all humans had brown eyes.
89
The largest cell in the human body is the female egg and the smallest is the male sperm.
682
A man's beard grows fastest when he anticipates sex.
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