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Bacteria have flourished on the earth for over three billion years. They were the first life forms on the planet.
Vaccines prevent between 2.5 and 4 million deaths every year.
There are 20 feet of blood vessels in each square inch of human skin.
Human kidneys will clean about 1 million gallons of blood in an average lifetime.
Although the Roman numeral for the number 4 has always been taught to have been "IV," according to historians, the ancient Romans probably used "IIII" most of the time. This is partially backed up by the fact that early grandfather clocks displayed IIII for the number 4 instead of IV. Early clockmakers apparently thought that the IIII balanced out the VIII (used for the number 8) on the clock face and that it just looked better.