The average person's skin weighs twice as much as their brain.
131
It took 200,000 years for humans to reach 3 billion in number. It took 40 years for the next 3 billion.
11
The largest cell in the human body is the female egg and the smallest is the male sperm.
682
Having sex can make a woman look younger and more attractive due to the release of estrogen and collagen.
346
An unprotected human can survive up to 1.5 minutes in space with no permanent bodily damage.
82
Shark corneas are used in eye transplants and shark bone marrow can be used to graft human bones.
132
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
Early American humans hunted car-size armadillos and used their shells for houses.
12