Yawns are more contagious among people with closer relationships.
163
One human hair can support 3 ounces.
191
There are times when you're walking that the pressure on your feet exceeds your body weight, and when you're running, it can be three or four times your weight.
62
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
It takes about 20 seconds for a red blood cell to circle the whole body.
102
The average sperm cell swims at 8 inches per hour.
76
The adult human brain weighs about 3 pounds (1,300-1,400 g).
99
The human brain doesn't stop developing until about 25 years old.
102