California's ethnic diversity could stretch back as far as 12,000 years, when different tribes settled in the area.
"For a number of years, people have shown a correlation between ecological diversity and linguistic diversity. What we did in this study that was different was to look at it over time - to actually see the process through which different populations came to live side-by-side as neighbors or replaced one population with another. We're showing how the diversity actually developed over time," Brian Codding, an assistant professor of anthropology and principal author of the new study, said, a University of Utah press release reported.
Codding said the problem of linguistic diversity, and why it is more prevalent in some areas and not in others, has been baffling anthropologists for some time.
The researchers looked at NASA images of "modern environmental productivity - known formally as net primary productivity." These images exhibit the overall richness of plant-life in the area,
After reviewing the images, the team created a map of the distribution of Native Americans in the area during the 1700s and 1800s.
The team found the "lushness" of certain local environments directly affected the "the order in which nine, major, prehistoric Native American ethnolinguistic groups migrated to California and colonized the state."
During the early period (known as the Holocene era), 12,000 to 8,000 years ago, the first settlers claimed the most fertile areas along California's coast. These settlers brought the Yukian, Chumash, and Hokan language groups.
In the middle Holocene era, which took place about 8,000 to 4,000 years ago, people started to settle further inland. These people were members of the Yok-Utian, Takic and Wintuan-Maiduan language groups.
During the late Holocene era, about 1,000 years ago, the population continued to move farther away from the coast. Algic and Athabaskan language groups replaced other weaker sects during this time.
The stronger groups may have had better hunting and fishing techniques which allowed them to "outcompete" the former residents.
"The final native people who came to California during the last 1,000 years - for whatever reason seem to have displaced people who had been in some of these highly productive places along the coast, particularly the northwest coast of California, from Mendocino north to Oregon," Codding said.
Researchers have not found evidence of violence in this alter period, but said the displacement could be due to a new-found idea of private property.
"We can use these general results to try to understand how ethnic diversity builds over time in different areas. ... If you look across the world, some places have a lot of different language families within a small area - New Guinea, for example - and others like the Great Basin just have one [Numic, used by Utes, Piutes and Shoshone peoples]. It suggests that where we see a lot of ecological diversity, migration patterns probably should result in the buildup of linguistic diversity," Codding said.
The researchers concluded that their methods "may aid in the explanation of prehistoric hunter-gatherer migrations across the globe, including the initial spread of people out of Africa into Europe, Asia and across to Australia-New Guinea."
