Yawns are more contagious among people with closer relationships.
163
The average sperm cell swims at 8 inches per hour.
76
After age 30, the brain begins to lose about 50,000 neurons per day - shrinking the brain .25% each year.
55
Enamel is hardest substance in the human body.
61
It takes about 20 seconds for a red blood cell to circle the whole body.
102
Your thumb is about the same size as your nose.
124
If every muscle in your body could pull in one direction, you could lift nearly 25 tons.
22