The oldest stone tools found are dated from 2.7 - 2.9 million years ago. The species that made these tools is unknown.
13
Pet dogs and elephants are the only animals that seem to instinctively understand human gesture.
14
The focusing muscles of the eyes move around 100,000 times a day. To give your leg muscles the same workout, you would need to walk 80km (50 miles) every day.
21
You forget 90% of your dreams.
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