The scientific study of twins is known as "gemellology." The word twin is said to have probably been derived from the ancient German word twine, which means 'two together.'

Worldwide there are said to be at least 125 million living multiples. The incidence of twin types and genders are oddly symmetrical.

Another surprising fact is that up to 22% of twins are left-handed. In the non-twin population the number is just under 10%. Another interesting tidbit is the average time between the delivery of the first and second twin is 17 minutes. Every year twins' birthrate increases! Some scientists say it depends on the pregnant women's age, which has also been increasing recently.

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