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Reliability of distant Geneanet matches

Discussions regarding DNA & Genetic Genealogy.
lisamar
female
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So far Geneanet has only found distant matches for me.

The closest of these distant matches shows shared DNA of 0.5 % and 37.1 cM. The closer distant matches come from countries where I have ancestors and relatives.

However, I also have a very long list of French matches as well as some Spanish, Italian and Portuguese matches (as based on names and family trees). Here the figures might be just 0.1 % of shared DNA and 7.1 cM. Could these still be an indication of ancestry from these regions or do most Geneanet members get a high number of false matches, e.g. from France?

Thanks for any theories or advice
ericdubois
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0.1% could mean a very distant MRCA or be a false positive. I wouldn't spend too much time on those matches as the odds of finding that ancestor are very slim.

More importantly, having matches in another country does NOT mean you have ancestors in that country. Some distant cousins may have immigrated to that country. A common example is that most Europeans will find US matches and have no ancestors in the US. However, they have cousins there.

Eric
lisamar
female
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Thanks, Eric. It may be best to focus only on the green matches and possibly the orange ones.

Since this is a French site with many French users, I was wondering if there’s a greater likelihood of getting both false and genuine French matches as compared to US sites. Family trees show French ancestry from the 1600s.
ericdubois
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It's almost impossible to identify an ancestor from the 1600s through DNA. You only share about 0.1% of DNA with an ancestor 10 generations back, and all his/her descendants currently alive also share that amount. That means you and your 10th cousins might only share 0.0001% of DNA through that ancestor.

However, there is a certain amount of endogamy in most regions, with the same families inter-marrying. The combined segments inherited from all these ancestors could point you to a specific region or even a specific town. But only traditional genealogy will confirm the common ancestor.

Recreational DNA tests are still illegal in France and I'm not sure what percentage of members who have uploaded their DNA is actually French.

Eric
lbrty4all
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It is true the farther back the connection the more difficult it would be, but there are variables.

You would get the highest quality matches by merging multiple raw DNA files: "adding more SNPs to your raw data and getting more overlap will tend to disprove matches that might otherwise have been thought to be valid...Combining raw data from different companies does seem to provide some degree of increased accuracy in your match information and eliminates a few incorrect segments. Using it will drop off some of your more distant matches from your match list and replace them with others."

The whole post is worth studying
https://www.beholdgenealogy.com/blog/?p=2717
lbrty4all
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General information--but it's a fast changing discipline!

https://isogg.org/wiki/Autosomal_DNA_statistics

and

https://isogg.org/wiki/Identical_by_descent

and worth a read here

In defense of small segments
https://segmentology.org/2020/01/31/in-defense-of-small-segments/

Also, there are significant variables (if your parents are related or there's endogamy where people in the same place or of the same religion intermarried for generations) in analysis.
jcgodlew
jcgodlew
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I have found a DNA ancestor born in 1635. So it does work. While 50% of my DNA is French, and I have found many cousins by matching data. Only one distant DNA match. Must be the legality issue under French law.
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