It took 200,000 years for humans to reach 3 billion in number. It took 40 years for the next 3 billion.
11
Our eyes are always the same size from birth, but our nose and ears never stop growing.
266
Tigers can see 6 times better at night than humans.
305
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
Women have about four times as many foot problems as men; lifelong patterns of wearing high heels often are the culprit.
111
Your fingernails grow faster in summer.
744