When you upload DNA results to a free GEDmatch account, you get access to a set of tools to explore ethnicity and DNA relatives.
The GEDmatch website uses the term “admixture” for techniques that attempt to calculate the different geographic origins within your DNA.
Ancient Versus Recent Admixture Estimates On GEDmatch
There is a major difference between GEDmatch and the big DNA testing websites when it comes to ethnicity or admixture.
GEDmatch admixture projects are largely focused on ancient ancestry going back as far as nine thousand years.
The top DNA testing websites include Ancestry.com, 23andMe, and MyHeritage. Their ethnicity estimates are mostly focused on a timeframe of a few hundred years. 23andMe has a Neanderthal estimate, but that is an exception.
They compare your DNA test to groups of DNA samples from living (or recently living) volunteers. Some of the volunteers are their own customers, but the companies also use DNA samples collected by large academic research projects.
Ancient DNA samples in academic research projects
The academic research projects may include DNA samples collected from ancient human remains at archaeological digs.
When sites like Ancestry or MyHeritage gather DNA samples as reference groups, they usually exclude the ancient samples.
This is the difference with the admixture projects on GEDmatch. Most GEDMatch projects use the archaic DNA samples as a big part of their calculations.
How Far Back Do GEDmatch Admixture Estimates Go?
Different projects and calculators use different sets of DNA samples as part of their estimates. You can dive into the exact details using the GEDmatch Oracle feature.
For example, some of the Eurogenes calculators use DNA samples classified as Early Farmers or Hunter-Gatherers. This time frame is the 7th Millenium BC. In other words, that is seven to six thousand years BC!
Don’t let the “MDLP K11 Modern” calculator fool you with “Modern” in the title. This calculator is focused on Mesolithic and Neolithic periods. It tries to distinguish Eastern from Western Hunter Gather components in your DNA using specimens from archaeological digs.
Other calculators look for Ancient South Indian admixture or South African hunter-gatherer – to name a few.
Which calculator should you use?
I have a series of articles that cover each of the GEDmatch admixture projects. Depending on your background, some will be better than others.
You can read our round-up guide to GEDmatch calculators which looks at the best calculators for different GEDmatch users. It will give you links to the in-depth articles.
GEDmatch health warning
The general advice is to take your GEDmatch estimates as being interesting but possibly highly inaccurate.
I’ve put lots of caveats and warnings into the in-depth articles on each calculator. I’ll mention here that there is an inherent difficulty with dealing with ancient DNA samples: there aren’t that many of them!
Ancestry.com and 23andMe can collect thousands of DNA samples to represent individual ethnicities.
In contrast, the GEDmatch projects are dealing with handfuls of samples.
The calculators are based on statistical analysis, which may become meaningless at such low sample numbers.
For example, some of the Gedrosia calculators give you an estimate of Ancient North Eurasian admixture. But there are only three “real” DNA samples in this reference group. I go into more detail in our in-depth guide to the Gedrosia project.
Exploring Shared DNA With Neanderthal And Other Ancient Specimens
You don’t need to rely on the admixture calculators to compare your DNA results to ancient DNA samples collected around the world.
We have a tutorial on using the GEDmatch Archaic DNA Matches tool to explore Neanderthal and other archaic DNA matches.
You can also use the standard One-To-One comparison tools on specific samples. Check out our tutorial on comparing your DNA to ancient Irish DNA samples on GEDmatch.
How Many Generations Do DNA Matches Go Back On GEDmatch?
GEDmatch applies a minimum threshold of 7 cM of shared DNA when showing you DNA matches in their One-To-Many reports.
This is one centimorgan lower than Ancestry.com or MyHeritage. At this low level, you are dealing with potential 8th cousins or more.
Always bear in mind that you could also be dealing with false positives due to chance.
This handy table shows you how your more distant cousins could fit into your genealogical family tree:
Be wary of lowering the cM threshold
Some of the GEDmatch tools let you drop the cM threshold down below 7 cM.
This is how you can compare your DNA to the Neanderthal and other ancient samples uploaded to the site!
But you can lower the cM threshold for a One-To-One comparison with any DNA kit on GEDmatch.
The free tool lets you go down to 3 centimorgans. The Paid Tier lets you go even lower. I advise against this unless you’re doing some fun exploration of the archaic matches.
You may be looking to validate what you suspect to be an 8th cousin. But if you drop the minimum cM threshold to such low levels, you’ll get inundated with tiny segments of shared DNA due to chance.
How can you distinguish between noise, false positives, and tiny segments that are inherited from common ancestors? Right now with the current technology…we can’t.
What About Other DNA Websites?
Check out our articles on these other sites:
More Articles And Tutorials?
GEDmatch is notorious for its steep learning curve. The first thing you’ll need to do is to follow our tutorial to upload your DNA results to the GEDmatch site.
Then you can follow our tutorials on every GEDmatch feature that will make it easy to get up to speed.
You can also get notified of new articles and tutorials about the site.