...for tens of thousands of years, the Khoisan's ancestors were members of "the largest population" on the planet, according to a new study. The Khoisan have long stood apart from other groups within Africa. They look distinct, speak in "click" languages, and have also maintained the greatest genetic diversity known among human populations. Usually, big populations harbor the most diversity. But census counts show that the 100,000 Khoisan speakers in Africa today are far outnumbered by other groups, such as the 45 million Bantu speakers and their 180 million descendants who now speak Swahili and other languages. Researchers have thought...