Kinship and Distance

The above chart shows the relationship between my relatives and their physical distance from me. If you read my preceding post you’ll see that 23andMe provides a map showing the location of one’s DNA relatives (for those who have shared that information). That made me wonder how far (or close) people people generally move or settle in relation to their family.

I’ve lived in several cities around the country including Seattle and New York, and even Tokyo, Japan for my senior year abroad, but I ended up settling for my adult life about eight miles from where I grew up in the San Jose area. In the above chart, degree 1 includes my closest relatives, i.e. those people who share 50% of my DNA, which is my children, siblings, and parents. Degree 2 is those with 25%, such as grandparents, aunts, uncles, nieces, nephews. Using my own genealogical information and family knowledge, along with a few Google searches, I was able to go out as far as some second cousins (Degree 5). The 6th level shown is taken from that 23andMe map. I used all the 3rd cousins I could find on that map, and no doubt that relationship is only estimated based on shared DNA, not actual generational kinship. Most of those shown on the map were 4th cousins or higher.

The vertical axis is logarithmic, so the actual increase in distance as the kinship increases is much greater than it appears. The trend line shown is exponential, which ironically looks straight because the Y-axis is already logarithmic. In my case, then, it seems clear that generally the more distant the kinship (i.e. “blood” relationship) the farther my relatives are from me. I suspect that is true generally, but I’d be interested in seeing demographic trends for the U.S. and world populations. I’d guess that in the less developed countries, families stay closer together for more generations. I found dozens of charts and articles online, but none that answer this question directly. Of course, such demographic trends change, and can do so rapidly. A number of recent articles mention how more millenials are living with their parents, reversing the trends of recent years. Whatever the trends, it’s fun to see how widespread my family is, even if I don’t know many of them.

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