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
Modern humans first appeared about 200,000 years ago, but record keeping didn't begin until about 6,000 years ago. That means about 97% of human history is lost.
21
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
The world's shortest man measures only 21.5 inches.
73
The human brain is very soft, having a consistency similar to soft gelatin or firm tofu.
13
You can't tickle yourself.
29