What you call your ancestry will depend on what point in history you are looking at. This map is designed to show a geographical location and the concentration of our common ancestors descendants from that point in history.
The SHADING OF AREAS represents the similarity of your autosomal DNA to our regions. We start off with a time period close to present day and show your estimated autosomal admixture at that time period. Like in your family ancestry percentages, the darker areas represent more genetic similarity. As the slider moves further back in time, other areas get highlighted, showing that the further you go back in time, your genetic similarities to other areas and populations increase, until we reach a point back in time where "we are all made up of all of us".
In brief, this plot shows where you have relatives “today” (1492AD before the colonial era migrations), shared through all of the ancestors that were alive a given number of years ago. In more detail, looking far enough back in time, we all share our whole genome with everyone in the world. Very recently we each share direct ancestry with only a few people. At more interesting timescales, we share ancestry differently with populations across the world.
This feature aims to explore how your ancestry sharing with people alive today changes as we move back in time. The DOTS ON THE MAP illustrate human population density today, with approximately one dot per million people. There are more dots in the regions where the largest numbers of descendants of your ancestors, at different times in the past, now live.
For technical reasons, we are currently unable to detect shared ancestry less than 5% with this method. You may be aware that most people share many ancestors with most other people, even on very recent timescales - around one thousand years within Europe (Ralph and Coop, 2013). However, you have so many relatives 1,000 years ago that these few “unusually distant" relatives account for only a small fraction of your whole genome. You will therefore see ancestry with distant places appearing only when it reaches 5% of your genome, at the detection limit of our approach.
It is very important to note that whilst you know where your relatives live today, we don’t know where your ancestors lived. For example, if you are European, you will share ancestry with India via ancient people that spoke an Indo-European language, but the locations of these groups are still a subject of academic debate (e.g. It is likely to include the steppe, but may also include Anatolia or other locations). As another example, Eurasians will have Native American relatives, shared from before the ancestors of Native Americans crossed the Bering Strait; in this case we know that these ancestors never actually visited the Americas, but the descendants of those ancestors did.
Finally, we note that this is a development feature that uses an unpublished model of ancestry shared via ancient populations. We will continue to improve and test this and future models, and therefore your results are potentially subject to significant change, as accuracy increases.
Ralph and Coop (2013) "The Geography of Recent Genetic Ancestry across Europe”; PLoS Biology 11:e1001555.