Massive genome-wide study in the United States has revealed a ‘historical portrait’ of post-colonial population patterns across the country.
Following the arrival of Columbus and his contemporaries, population expansion in the Americas has proceeded at an exceptionally rapid pace, with factors such as war, slavery, disease and climate shaping human demography.
The first cluster, they say, likely came about from population structures that existed prior to immigration to the US. This included clusters of Finnish, Scandinavian, Jewish, and Irish ancestries – groups who came to the country in large numbers within the last 200 years – as well as African Americans and individuals of Polynesian ancestry.
In addition, the team included Acadians and French Canadians, who they found to have clusters with ‘clear geographic concentrations both within and outside the United States.’
Admixed clusters largely represented Hispanic/Latino populations, including groups from Colombia, Central America, and the Caribbean.
African Americans: This group appeared to originate in the US in the coastal plans of North and South Carolina, pushing west until it hit eastern Texas. According to the team, the pattern coincides with regions that have both high self-reported African ancestry and regions that historically practiced slavery.
European Jewish: This was one of the largest clusters found in the study. This cluster was most strongly represented in New York and Chicago, where large numbers of Jewish immigrants arrived in the late 1800s and early 1900s.
Portuguese: The many Portuguese immigrants began to come to the US in the late 19th century, flocking to the eastern US, the study does not reflect this. But, it does show immigration to a number of cities in California, including the San Francisco-Oakland Bay Area, Santa Cruz, the Central Valley, and San Diego.
Eastern Europeans: Between 1840 and 1870, they found that immigrants mostly came from Hungary, Poland, Austria, Slovakia, Czech Republic, and Italy, heading for New York and Pennsylvania.
Northern Europe: This cluster included Finnish, Swedish, Danish, Norwegians and Scandinavians. These groups came to the country in large numbers within the last 150-200 years.
Irish: According to the researchers, six million Irish came to the US in the 19th century.
Admixed clusters largely represented Hispanic/Latino populations, including groups from Colombia, Central America, and the Caribbean.
The third group, accounted for the majority of the samples, with the five largest clusters described as assimilated immigrant clusters. One of these clusters is the Pennsylvania cluster, accounting for massive amounts of Germans that arrived in the country in the 1700s. About 80,000 Germans immigrated between 1717 and 1775, settling in Philadelphia, southeast Pennsylvania, and New Jersey.
Once the first wave of immigrant families is established, their success encourages others to follow them. So the Irish and the Germans soon become a significant proportion of the American population. The figures are striking. In 1860 approximately 4 million residents in the United States have been born elsewhere – some 1.6 million in Ireland and 1.3 million in Germany (compared to about half a million in England, Scotland and Wales).
When combined with their children born in the States, these figures suggest that the new Irish and German communities are each already about 3 million strong – perhaps as much as 10% of the population (31 million in 1860). And these figures are in addition to older Irish and German groups already present in colonial times.
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