It took 200,000 years for humans to reach 3 billion in number. It took 40 years for the next 3 billion.
11
Poor eyesight (myopia) is associated with higher IQ.
232
The human sigh acts as a physiological reset button.
23
Blue eyes are a genetic mutation. Before the mutation occured, all humans had brown eyes.
89
It takes about 20 seconds for a red blood cell to circle the whole body.
102
A person will create enough saliva to fill two average size swimming pools during his lifetime.
191
The average person will go on a date at least 100 times before they finally marry.
33
The average person's skin weighs twice as much as their brain.
131