As has been covered here on the front page and in a recommended diary, the dumpster-fire-in-chief once again has invoked one of the names of Matoaka, a native American teenager made famous by English settler John Rolfe, as a slur against Massachusetts Sen. Elizabeth Warren at a ceremony honoring the Navajo Code Talkers. Needless to say this action by said dumpster fire is to be condemned in no uncertain terms.
However…once again I see people invoking DNA as being able to prove native American ancestry. As a genealogist and genetic genealogist, I’d like to address that. DNA has become an invaluable tool for genealogist to unlock secrets of the past and break through brick walls in genealogical research, but it is not unto itself the indispensable magic bullet that people think.
If you have a family oral history that claims native ancestry as exists in Elizabeth Warren’s family, taking a DNA test may not fully prove or disprove the claim. If you take an autosomal DNA test offered by many companies such as Family Tree DNA, Ancestry DNA or 23 and Me, they will test approximately 700,000 locations on your autosomes, X chromosome and at some companies, a small part of your Y chromosome (men only). That is out of the 3 billion or so locations in your nuclear DNA (autosomal DNA plus the sex chromosomes). From those 700,000 locations, they will compare your results to their reference populations for each of their ethnic regions and compute a percentage for each. But your results can vary between companies because of the reference populations used as the basis of the ethnogeographic breakdown. These reference populations are often based on modern peoples and may not fully capture the genetic variation of populations from 500-1000 years ago these populations are chosen the represent.
Assume for a moment that the results do show native American ancestry. Does that prove you are Native American? Not necessarily. If the percentage is small, it could statistical noise, that the combination of results may look sufficiently similar to their reference population for Native Americans to trigger it being added to your results without in fact being Native American in origin. There are tools that can be used to paint your results probabilistically by ethnicity. If you can locate a longer segment of DNA with a high probability of native origin, then you can start to believe the determination of Native American ancestry. If you don’t have longer segments (generally 7 or more centiMorgans) with such high probability, the identification of Native ancestry may be suspect.
Assume for a moment the results don’t show Native American ancestry. Does that disprove Native ancestry? Not Necessarily. Depending on how far back the native ancestor is, it is entirely possible that none of their DNA is represented in your genome. At each generation when the DNA is passed down, it undergoes recombination where the parents’ chromosomes pair up and swap random segments with each other to create a new chromosome that will be passed down. Under most circumstances, you will get one of each chromosome from each parent insuring you are 50% your mother and 50% your father. However, there is no guarantee that the 50% you got from your father is 50% his father and 50% his mother. On average it will be 50/50, but any one event it will fall along a bell curve (normal distribution) of probability. For example, of the 50% of my DNA I got from my father, about 62.2% of it came from his mother while only about 37.8% came from his father. As a result of these uneven, random recombinations, after several generations, you may have genealogical ancestors who are not genetic ancestors.
According to the International Society of Genetic Genealogists
[S]ome relationships will not be detected purely because of the random nature of autosomal DNA inheritance which means that we do not inherit DNA segments from every genealogical ancestor. The number of detectable relationships decreases with each generation. At ten generations we have approximately 1024 ancestors although there is generally some overlap as a result of pedigree collapse. While all these ancestors can potentially be documented in our genealogical tree we only inherit segments of DNA from a small subset of these ancestors. Luke Jostins found that "The probability of having DNA from all of your genealogical ancestors at a particular generation becomes vanishingly small very rapidly; there is a 99.6% chance that you will have DNA from all of your 16 great-great grandparents, only a 54% [chance] of sharing DNA with all 32 of your G-G-G grandparents, and a 0.01% chance for your 64 G-G-G-G grandparents. You only have to go back 5 generations for genealogical relatives to start dropping off your DNA tree.
So, if you have a full-blooded native ancestor who is a GGG grandparent, their DNA might not be in you. And if that native ancestor wasn’t full-blooded, the chances are even lower that their DNA will be represented in you, assuming those segments can be detected by comparison to the reference population I mentioned above.
If you’d like to read more about this, please see my previous diary on this topic: On Trump, Brown, Warren, DNA and what it is to be American from the last time the DNA angle was brought up in response to you know who’s attempt to slur Sen. Warren.
I won’t be able to respond to comments as I’m getting ready to get on a plane for 4 hours. I’ll try to come back and respond when I get home. Thank you.