It takes about 20 seconds for a red blood cell to circle the whole body.
102
On average, there's 100 billion neurons in the human brain.
83
Yawns are more contagious among people with closer relationships.
163
The human eye blinks an average of 4,200,000 times a year.
233
The human sigh acts as a physiological reset button.
23
Poor eyesight (myopia) is associated with higher IQ.
232
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