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Although puberty usually occurs in the early teenage years, the world's youngest parents were two Chinese children who had their first baby when they were 8 and 9 years of age.
About 3% of all pregnant women will give birth to twins, which is an increase in rate of nearly 60% since the early 1980s.
Only one in 10 cancer deaths is caused by the primary tumor. The vast majority of cancer mortality is caused by cells breaking away from the main tumor and metastasizing to other parts of the body, such as the brain, bones, or liver.
More than 2,500 barbiturates have been synthesized. At the height of their popularity, about 50 were marketed for human use.
Pope Sylvester II tried to introduce Arabic numbers into Europe between the years 999 and 1003, but their use did not catch on for a few more centuries, and Roman numerals continued to be the primary number system.