I really can't praise the work of the volunteers at Gedmatch enough, they do a superb job. If you have done a DNA test via 23andme or FamilytreeDNA Family Finder and you are interested in finding more clues about your ancestry do upload your data to Gedmatch. It is anonymous and you are identified via an ID number and your emal should you wish to submit it (this allows potential cousins at Gedmatch to contact you).
Once you have uploaded your data to Gedmatch it is safely stored and you merely enter your ID number whenever you wish to check anything, so no messy uploading of your raw data files everytime!
They have recently added some "admixture calculators" which you can run your data through. These predict how much of your DNA comes from certain regions of the world. It's all based on statistics and I don't know how they do it, but it's interesting! It is through these calculators that I have been able to see that my mother has some Eastern European ancestry based on her higher scores compared to people who are 100% British. And really to use these calculators and make any sense of them, you need to compare your scores to people of a similar ethnic origin to you, right down to similar regions of a country if you can.
You can easily compare your results by posting them on the forums at 23andme and FTDNA-search for Gedmatch in each and you will find a multitude of threads about it!
One handy thing about Gedmatch is it allows you to reduce the "safe" threshold of 7cM (Centimorgans, a unit of measurement of DNA) and 700 SNPs (the little bits that make up segments of DNA).
23andme and FTDNA use thresholds around this number to make sure that the matches you get to other people are real and not just "noise." But many people have been successful at finding connections to people below this safety net cut off. It must be used with caution though. It has been suggested by some that anything between 5cM and 7cM has a 50/50 chance of being from a shared ancestor within a genealogical timeframe. It is possible that segment this small could be ancient throwbacks representative of an ethnic group rather than a specific family from the ethnic group. It could also be the computer that works it all out having a bit of a moment and joining to little fragments of DNA together (eg a tiny bit from your Mum and a tiny bit from your Dad) to make a bigger one which it thinks is worthy of a mention. 23andme and FTDNA do allow you to experiment below the 7cM threshold (see Ancestry Finder at 23andme or play around with the chromosome browser at FTDNA) and 23andme advise anything near to 5cM be taken with a pinch of salt.
So why would you want to use Gedmatch to go below this threshold? Perhaps I am missing out, but I do ignore anything below 6cM, however I decided to compare my mother's 5th cousin of Szekely descent and this cousins Granddaughter using 3cM! Shock horror, I don't know what came over me, I blame my recent root canal.
Sure enough they shared little segments with my Mum, some were the same others different. So I focussed on the segments that they shared in common with each other and my Mum (this would infer that the Grandmother had passed them to the Granddaughter). One segment in particular was on chromosome 18 both roughly 3.7cM and 648 SNPs.
I had been intrigued by a mystery Gedmatch user that was clearly related to both of them, so I decided to compare them to my mother too. Sure enough, they matched in this location too. I emailled the person in chrage of looking after the family Gedmatch accounts and it turns out the mystery match is the Grandmother's son!
So there is a small segment that has been passed from mother to son to daughter that is also shared by my mother via a shared ancestor in the past! Or at least that is how it appears, I have to take it with a pinch of salt but it seems plausible to me!
Gedmatch also ran a rare SNP feature which has since been removed and will have it's own website, which allows you to see what rare SNPs you have which may suggest a connection to a region.
Whilst it was still available I was able to compare my mother to the Grandmother and the Granddaughter to see if they all shared any rare SNPs. They did, one. Origin of the SNP was listed as Spain, Poland or Hungary! As they both have Hungarian ancestry I was quite impressed! It doesn't prove any recent connections using this method, but it was nice to have it supported by people we knew had ancestry from Hungary.
So if you have data, get uploading! If you find new cousins or find something out about your ancestry via Gedmatch, please consider making a donation to support their hard work!
http://www.gedmatch.com/
