21 July 2013

Ancient Mitochondrial DNA, Many Matches Syndrome, Citizen-Scientists and Scientific Data

A recent story in the news illustrates several points I make in my genetic genealogy presentations. The story reports a scientific study that confirms genetic links between living members of the First Nations community and ancient remains in British Columbia:
A groundbreaking genetic study led by a team of U.S. and Canadian anthropologists has traced a direct DNA link between the 5,500-year-old remains of an aboriginal woman found on a British Columbia island, a second set of ancient female bones from a nearby 2,500-year-old site and — most stunningly — a living Tsimshian woman from the Metlakatla First Nation, located close to both of the prehistoric burials along B.C.’s North Coast near the city of Prince Rupert.1
It is jaw-droppingly amazing to read about scientific studies linking the DNA of someone living today with the DNA of someone who lived thousands of years ago, both in the same geographic area. I remember how excited I was to find out I shared mitochondrial DNA (mtDNA) with the Cheddar Man found in a cave in England and that my family shares Y-DNA with ancient horsemen roaming the Russian steppes. If my DNA had been matched to ancient remains on my doorstep I would still be floating on air.

Compared to the technology of only a decade ago, it is amazing for me to read about this study in my remote, rural location on a lazy Sunday morning. A quick Internet search links me to several news stories on this event as well as genetic genealogy blog posts.2

Even more amazing is that I can quickly find the paper written by the scientists doing the research.3 I can download it from the open-access, peer-reviewed journal website along with the supplemental data—all at no charge. (Every serious genetic genealogist should become familiar with PLOS—Public Library of Science—and PLOS ONE.4)
I can see exactly where and how many DNA mutations there are that separate the ancient and modern British Columbia mtDNA samples—only a handful. The scientific paper includes the GenBank assession numbers for the DNA samples referenced in the paper.5 I can access the DNA signatures and use them in my own studies. GenBank is a database storing publicly available DNA sequences:
The GenBank database is designed to provide and encourage access within the scientific community to the most up to date and comprehensive DNA sequence information. Therefore, NCBI places no restrictions on the use or distribution of the GenBank data. However, some submitters may claim patent, copyright, or other intellectual property rights in all or a portion of the data they have submitted.6
Aside from all of the really amazing facts above about access to scientific data by non-scientists or citizen-scientists, this story also demonstrates why it can be more difficult to use mtDNA for genealogical purposes. The frequency of mutations in Y-DNA often lead to enough changes in a few thousand years that we can find a common ancestor in a genealogical timeframe. The frequency of mutations in mtDNA seldom lead to enough changes in a few thousand years that we can find a common ancestor in a genealogical timeframe. Notice I used the words often and seldom. I did not use the words always and never. The random nature of DNA mutations makes it impossible to know what you will see until a test is done. That random mtDNA mutation needed to prove your genealogical theory could have happened four or five generations ago instead of dozens. There are some genealogical questions, but not all, that can answered emphatically with the right DNA test. Many Matches Syndrome describes a lot of matches seen with a low resolution test. And family trees may not go back far enough to find a common ancestor when you match someone on a high resolution test such as the full mtDNA sequence.

I strongly encourage anyone interested to take a DNA test for genealogical purposes. But if you want to use the test results as evidence you should understand what you can and cannot do with DNA test results. And you need to be prepared to spend time studying what the results mean. You won't receive a piece of paper with the answer to all of your genealogical questions written in plain language. You will have to learn some of the science.You will have to contact those with matching DNA and compare family trees to find a common ancestor. But that is part of the fun and there are many educational opportunities for genetic genealogists today. See posts in DNA, Education, and Speaking schedule categories on this and other genetic genealogy blogs.

1. Randy Boswell, 'Breakthrough DNA study links B.C. woman and 5,500-year-old “grandmother”,' Postmedia News, 6 July 2013 (http://www.canada.com/technology/Breakthrough+study+links+woman+year+grandmother/8622672/story.html : accessed 21 July 2013).
2. Roberta Estes, "5,500 Year Old Grandmother Found Using DNA," DNAeXplained blog, posted 10 July 2013 (http://dna-explained.com/2013/07/10/5500-year-old-grandmother-found-using-dna/ : accessed 21 July 2013).
3. Yinqiu Cui, John Lindo, Cris E. Hughes, Jesse W. Johnson, Alvaro G. Hernandez, et al., "Ancient DNA Analysis of Mid-Holocene Individuals from the Northwest Coast of North America Reveals Different Evolutionary Paths for Mitogenomes," posted 3 July 2013, PLoS ONE 8(7): e66948, doi:10.1371/journal.pone.0066948; (http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0066948 : accessed 21 July 2013).
4. "About," Public Library of Science (PLOS) (http://www.plos.org/about/ : accessed 21 July 2013); "a nonprofit publisher, membership, and advocacy organization with a mission to accelerate progress in science and medicine by leading a transformation in research communication." Also "PLOS ONE Journal Information," PLOS ONE (http://www.plosone.org/static/information : accessed 21 July 2013); "... an international, peer-reviewed, open-access, online publication."
5. Yinqiu Cui, et al., "Ancient DNA Analysis of Mid-Holocene Individuals from the Northwest Coast of North America," 5 (mutation), 6 (GenBank assession).
6. "GenBank Overview," GenBank,National Center for Biotechnology Information, U.S. National Library of Medicine (http://www.ncbi.nlm.nih.gov/genbank/ : accessed 21 July 2013).

To cite this blog post:
Debbie Parker Wayne, "Ancient Mitochondrial DNA, Many Matches Syndrome, Citizen-Scientists and Scientific Data," Deb's Delvings Blog, posted 21 July 2013 (http://debsdelvings.blogspot.com/ : accessed [date]).

© 2013, Debbie Parker Wayne, CG, CGL, All Rights Reserved

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