Yawns are more contagious among people with closer relationships.
163
Every year your body replaces 98% of your atoms.
119
If every muscle in your body could pull in one direction, you could lift nearly 25 tons.
22
Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
Dogs can be trained to identify the scent of lung cancer long before symptoms develop.
190
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