Yawns are more contagious among people with closer relationships.
163
The average sperm cell swims at 8 inches per hour.
76
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
Oxygen, carbon, hydrogen and nitrogen make up 90% of the human body.
118
The adult human brain weighs about 3 pounds (1,300-1,400 g).
99
Quick naps not only improve your alertness, but they also help in decision making, creativity and sensory perception.
149
Enamel is hardest substance in the human body.
61
When you get goosebumps and your hair stands, the hair helps to trap air, making you feel warmer by keeping in your body heat.
46