File:SNP global similarity report - Jesse Plamondon-Willard.png

{{image |description = A report showing the global similarity of Jesse Plamondon-Willard's genetic single-nucleotide polymorphisms to those of Northern European populations. Taken from 23andMe's global similarity (advanced view) report. |transcript =

Northern European
Northern Europe's prehistory was shaped by the advancement and retreat of ice sheets during the Ice Age, which reached its peak about 18,000 years ago. At that time the region was nearly uninhabited, covered mostly by mile-thick ice sheets and vast stretches of frozen tundra. But when the ice began to retreat about 15,000 years ago, the ancestors of many present-day northern Europeans moved northward from Iberia, the Balkans and the Italian peninsula.

We consider the Alps and Pyrenees to divide southern and northern Europe, the Caucasus Mountains and Caspian Sea to separate Europe from Central Asia and the Ural Mountains to delimit northern Europe and Siberia. The 23andMe database currently includes northern Europeans representing residents of western Russia, France and the Orkney Islands north of mainland Scotland. Our database reflects some of the genetic diversity of northern Europe prior to the era of intercontinental travel that began roughly 500 years ago.

English
The prehistory of the United Kingdom was shaped by the advancement and retreat of ice sheets during the Ice Age, which reached its peak about 18,000 years ago. At that time the region was totally uninhabited, covered entirely by mile-thick ice sheets. But when the ice began to retreat about 15,000 years ago, the ancestors of many present-day British moved northward, probably from Iberia or the Italian Peninsula. The genetic diversity of the United Kingdom reflects the history of these post-Ice Age human expansions, as well as much more recent migrations from continental Europe.

We consider the United Kingdom to refer to the present-day nation of the United Kingdom, located west of the North Sea and east of Ireland. Our database reflects the genetic diversity of the United Kingdom prior to the era of intercontinental travel that began roughly 500 years ago.

French (various regions)
The French population is a diverse one thanks to their country's wide range of landscapes, including the coastal plains of the north and west and the mountain ranges of the south and southeast.

About 2,500 years ago the region was occupied by people called Gauls, who spoke Celtic languages. Just over 2,000 years ago the Romans under Julius Caesar conquered the region, imposing their culture and language. Five hundred years later, Germanic speaking peoples, including the Franks (from whom the name France is derived), invaded the eastern part of the region controlled by the Gauls. Today French culture and genes reflect the influences of each set of peoples.

Today France, like many European countries, is undergoing a challenging transition to a multiethnic society. About 8% of its 64 million people were born outside the country, mostly in France's former African colonies.

23andMe's reference database includes 25 native-born individuals from different regions within France.

...my placement on the Global Similarity plot.
How does 23andMe place me on the advanced view of Global Similarity? We use a standard mathematical technique called multidimensional scaling (MDS) to produce the map. It takes the set of genetic distances between a bunch of people and uses them to make a two-dimensional map. We use only SNPs from the 22 autosomes. Full details of the procedure may be found in our white paper, but the main idea is that the closer you are placed to a group of reference individuals on the map, the more likely it is that your ancestors came from the same place as the reference individuals.

There are a couple caveats to the above. First, the advanced view of Global Similarity is not well-suited for people with mixed ancestry. The technique we use to place you on the map will position you according to the weighted average of your ancestry, which may not accurately reflect what you know about your family. For example, if your father is English and your mother is Chinese, you will be placed about halfway between the English and Chinese reference populations on the map, closest to the Central/South Asian reference individuals. If you have mixed ancestry, you may find our Ancestry Painting feature more informative.

Second, the distances between points on the map are only approximate genetic distances. Although the approximations are usually close, this means that your position relative to your friends and family may shift a bit in between views. For a more precise assessment of your genetic distance to friends and family, please see our Compare Genes feature.

...the difference between this plot and a map.
Is this the same as a geographical map? No. The advanced view of global similarity does not take actual geographic location of any of the people displayed into account. It is created using only the genetic data of real people. However, because the genetic differences between people in different parts of the world are largely a product of the geographic distances that isolated their ancestors, this view does resemble a geographical map.

...the reference populations.
Who are the reference populations? The reference populations are people from around the world who donated their DNA to research and gave permission for their data to be released to the public. We use the CEPH-HGDP and Illumina iControlDB samples. We are constantly adding samples to our reference database to improve the results of the advanced view of Global Similarity.

...what the squares on the map represent.
What do the squares on the map represent? Each square on the map represents an individual human being. They are color coded to indicate the person's population label. Having a particular label usually means that all four of the person's grandparents are from that population. We plan to add more reference populations

You, and your family and friends, are represented by people icons – green for the person whose similarity is being shown, a dark grey for everyone else (including the Mendels if their data is being shown).

...interpreting my plot if I'm of mixed ancestry.
How do I interpret my plot if I'm of mixed ancestry? The Global Similarity Advanced feature positions you on a map of the global gene pool according to a 'weighted average' of your ancestry. So if your parents come from widely separated populations you will end up between them, and most likely among people who do not share your ancestry!

For example, imagine someone with one English parent, and one Chinese parent. In the World view of Global Similarity Advanced, the English parent will appear amid European reference individuals (yellow squares) and the Chinese parent amid East Asian reference individuals (pink squares). Their offspring will appear about halfway between them. So even though their offspring's ancestry traces to England and China, he or she will appear amid Central and South Asian reference individuals (brown squares).

[diagram]

It's not just individuals with one generation of mixing who end up being placed on the map according to the average of their ancestry. For instance, someone with three Irish grandparents and one German grandparent will appear in the Northern European view between the Irish and German clusters, although nearer the Irish cluster than the German one.

...why people's positions shift when I switch between views.
Why do people's positions shift when I switch between views? You may notice that you and your connections (green and black cones), as well as the reference individuals (colored squares), can shift relative to one another when you switch between views, like when you switch from European view to Northern European view. Global Similarity Advanced does not perform an "optical zoom", like you'd see when you zoom in on, say, Google Maps. Here is what it does do:

As described here, Global Similarity Advanced is based on an algorithm that positions people on a 2-D plot so that the distances between the people in the plot match their true genetic distances as closely as possible. As you might imagine, the algorithm's results depend on which individuals are used to produce the plot. For instance, when Asians and Africans and Europeans are all coaxed into the same plot, as in the World view, the algorithm must accommodate the relatively large genetic distances between these groups, and these larger distances "swamp out" the smaller genetic distances that exist between more closely-related populations. In a view with more closely-related individuals, like Northern European, the algorithm will pick up on these finer distinctions, and thus both you and the reference individuals can move around a bit.

...the people linked to my account.
Who are the people linked to my account? You can compare genetic data with other people linked to your account. Anyone you added to your own account when you purchased their kit is automatically linked. To link other people, use the Genome Sharing feature.

Notes: with whom you can compare, even if your accounts are linked. account owner's maternal and/or paternal haplogroups in Paternal Line/Maternal Line ancestry.
 * If someone's data has not arrived from the lab, they will not be listed as someone
 * If you share with an ancestry.com demo account, all you will be able to see is the

If you don't have anyone linked to your account, we thought you might still like to be able to use the comparison features. You can compare yourself to anonymous Chinese, Japanese, and Nigerian donors whose samples were collected as part of the International HapMap Project. Note that these are not "average" Chinese/Japanese/Nigerian genotypes. They are real genotypes of actual individuals.

We've also linked you to profiles of an anonymous family nicknamed the Mendels. If you'd prefer not to see the Mendels or the HapMap people in your account, go to your Account Settings and uncheck the boxes under "Example Profiles." However in Ancestry Painting and some other features, the HapMap people are especially useful and always shown.

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