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October 26th, 2017 at 12:39 am

The immigrant maps of America: Genome study of over 770,000 people reveals the ancestral origins of each part of the country

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Scientists from AncestryDNA analysed genome-wide genotype data from 774,516 Americans

This allowed researchers to identify the genetic ‘clusters’ within, or the genetic communities

The study reveals ancestral origins and migration patterns for specific groups across the country

A massive genome-wide study in the United States has revealed a ‘historical portrait’ of post-colonial population patterns across the country.

The study analysed data from more than 770,000 people born or currently living in the US, allowing researchers to identify the genetic ‘clusters’ within.

In a series of maps illustrating the findings, the study highlights the ancestral origins and migration patterns for specific groups to reveal the many different genetic communities Americans belong to.

In the study, the researchers identified ‘clusters’ – or genetic communities – throughout North America using data from more than 770,000 people born or currently living in the US. The map shows the distribution of ancestral birth locations associated with these clusters.

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HOW THEY DID IT

AncestryDNA scientists analysed genome-wide genotype data from 774,516 Americans.

With this sample, the team then uncovered the patterns of ‘identity-by-descent’ (IBD).

IBD can ‘reveal signatures of recent demographic history,’ they explain in the paper.

By identifying groups of individuals that were slightly related to each other, they were able to spot the ‘clusters’ – or, genetic communities.

In the study, published to Nature Communications, AncestryDNA scientists analysed genome-wide genotype data from 774,516 Americans.

With this sample, the team then uncovered the patterns of ‘identity-by-descent’ (IBD).

‘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 researchers wrote.

‘We first created a network of genetically-identified relationships – based on DNA alone – among over 700,000 individuals who consented to research,’ the AncestryDNA team explains in a blog post.

‘Using network analysis techniques, we identified clusters of individuals in the network: groups of individuals who are slightly more related to one another than to individuals outside their cluster.

‘In other words, from genetic data we identified novel ‘population structure’ – subtly different groups of individuals within a larger population.’

The researchers grouped the clusters into four broad categories: intact immigrant, continental admixed, assimilated immigrant, and post-migration isolated groups.

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.

The third group, the researchers found, accounted for the majority of the samples, with the five largest clusters described as assimilated immigrant clusters.

Making up 60 percent of the samples, assimilated immigrants ‘exhibit a markedly different profile,’ the authors wrote, and lacked ‘distinctive affiliations to non-US populations.’

‘Genealogical data reveal a north-to-south trend, most consistently east of the Mississippi River,’ the authors explain.

‘These findings imply greater east-west than north-south gene flow, which is broadly consistent with recent westward expansion of European settlers in the United States, and possibly somewhat limited north-south migration due to cultural differences.’

The researchers also identified clusters that are thought to have experienced some form of isolation, whether geographic or cultural, though they maintained high levels of diversity and gene flow.

This includes the Amish, along with a group in Utah likely linked to the decedents of Mormon settlers, and a cluster thought to represent the residents of Appalachia, ‘who experienced delayed economic development and regional isolation up until the 20th century.’

The researchers say the analysis makes for a much finer picture of the genetic communities across the United States, and the histories behind them.

With this new methodology, the AncestryDNA team explains it’s now possible to see ‘how specific groups of people are connected through their DNA, what places they called home, and which migration paths they followed to get there – allowing genetics to reveal the history in a more recent time period than ever before.’

More details and charts at Daily Mail

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