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
It takes about 20 seconds for a red blood cell to circle the whole body.
102
Research has determined that most people are happiest at 7:26pm on a Saturday night.
69
The average sperm cell swims at 8 inches per hour.
4
Crying literally alleviates stress and uniquely allows humans to decrease feelings of anger and sadness.
24
A person will create enough saliva to fill two average size swimming pools during his lifetime.
191
The human brain doesn't stop developing until about 25 years old.
102
Tigers can see 6 times better at night than humans.
305