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The Babylonians wrote numbers in a system that used 60 as the base value rather than the number 10. They did not have a symbol for "zero."
The first-known contraceptive was crocodile dung, used in Egypt in 2000 BC. Condoms were also reportedly used, made of animal bladders or intestines.
As the western states of America were settled, pioneers often had to drink rancid water from ponds and other sources. This often resulted in chronic diarrhea, causing many cases of dehydration and death that could have been avoided if clean water had been available.
Though the United States has largely rejected the metric system, it is used for currency, as in 100 pennies = 1 dollar. Previously, the British currency system was used, with measurements such as 12 pence to the shilling, and 20 shillings to the pound.
Bacteria have flourished on the earth for over three billion years. They were the first life forms on the planet.
![(a) The Dmanisi cranium (right) shows similarities to early African H. erectus including the Narioko](https://biology-forums.com/gallery/47/medium_275510_22_02_15_6_06_47_20781142.jpeg)
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