A good rough estimate of metahuman populations in most areas is 1 for every 1,000,000 people. That would place the world population of metahumans at around 6,600. That may seem high to some, but consider the following points: metahumans include not only super-powered individuals, but those who are highly skilled, technologically enhanced, or trained in the mystic arts; not every metahuman may be aware of their abilities; not every metahuman chooses to don a skimpy outfit and fight other metahumans, many may use their skills to get ahead in business, attract members of the opposite sex, or simply personal enjoyment. Looking at how general population has increased over the years it becomes obvious why it appears that metahumans have begun to proliferate.
While there is no definitive proof, the history of metahumans appears to be tied in directly with early mythology and folklore. Researchers believe that tales of the more humanoid gods, heroes, and monsters may actually be early accounts of metahumans, and may help explain the distribution of metahumans today. Greek, Roman, Norse and Celtic myths are based heavily on human or humanoid figures. Indian myths to a lesser extent, as well as Egyptian, Babylonian, and Japanese. Myths based on less humanoid figures, such as those found in Native American, African, and Australian Aboriginal myths, seem to indicate a lesser likelihood of metahumans being found in great numbers in those regions.
Early heroic legends and epics may be historical accounts of early metahumans. The Germanic Beowulf and the Akkadian Gilgamesh epics, the stories of Robin Hood and King Arthur, Brian Boru, Finn McCool, and Siegfried seem to be likely candidates. The early American stories of Paul Bunyan, Pecos Bill, and others may be as well. Urban legends such as Spring Heel Jack, and regional legends like the Sasquatch and Abominable Snowman may have a metahuman basis as well.
When Greek and Roman people spread out across Europe, colonising and intermingling with native peoples, they likely spread metahuman genes to these areas, and much later they colonised Africa, Australia, and North America as well, bringing metahumans with them to areas that had not seen their like before. More so than other areas, America acted as a 'melting pot' for a variety of racial and ethnic types, including several that appear to have had a history of metahuman genes. This mix has resulted in a much higher incidence of metahuman creation than any other area. Areas that do not have this racial and ethnic crossbreeding, and generally a smaller history of metahumans as well, such as China, India, and parts of Africa, end up with a much lower population of metahumans on average.
In addition, most metahumans who are attempting to be heroes or villains are attracted to centres of high population, such as New York, Chicago, London, and Los Angeles. Villains go to these areas because of the higher potential in acquiring money, power, or whatever else they may be after. Heroes go there to stop the villains. Other 'public' metahumans go to these areas for the attention they can generate.