Yawns are more contagious among people with closer relationships.
163
Oxygen, carbon, hydrogen and nitrogen make up 90% of the human body.
118
The average sperm cell swims at 8 inches per hour.
76
Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
The adult human brain weighs about 3 pounds (1,300-1,400 g).
99
The human brain is very soft, having a consistency similar to soft gelatin or firm tofu.
13
After age 30, the brain begins to lose about 50,000 neurons per day - shrinking the brain .25% each year.
55