The oldest stone tools found are dated from 2.7 - 2.9 million years ago. The species that made these tools is unknown.
13
The largest cell in the human body is the female egg and the smallest is the male sperm.
682
It took 200,000 years for humans to reach 3 billion in number. It took 40 years for the next 3 billion.
11
Every human spent about half an hour as a single cell.
144
After age 30, the brain shrinks a quarter of a percent (0.25%) in mass each year.
139
It takes about 20 seconds for a red blood cell to circle the whole body.
102
If Earth's life was compressed into 1 year, then humans would have been around for only 2 seconds.
15
Tigers can see 6 times better at night than humans.
305