Heritavia
Heritavia · Notes

Matches, segments, the letter

GEDmatch does not email you about new matches. You have to open the list yourself, and start with the long segment, not the sum.

Vitaly Khoruzhko

Series. Overview · 1. File · 2. Profile · 3. Projects · Choosing · 4. Matches

Once the administrator has approved the application, there is no point in simply waiting for new relatives. GEDmatch does not send letters about fresh matches. New people in the list are highlighted for a while, but if you never open the list you will not know about them. One-to-Many is worth opening again when someone joins the project.

The list first, then two specific kits

Start with One-to-Many on your own number. This tool shows people who have DNA similarity with your kit. Results are sorted by the amount of shared DNA. The top of the list is where to begin: the largest matches are there, and with them it is easier to see whether there is anything to hold on to at all.

The total shared DNA matters. For genealogy it also matters how that DNA is spread across segments. Two people can have a similar sum and a completely different kind of match. One long piece and a scatter of short scraps are not the same story.

So look at:

  • how many segments;
  • how large the biggest one is;
  • where they lie on the chromosome;
  • whether someone among relatives you already know shares them;
  • which places and surnames stand in the trees.

Then move to One-to-One. It compares two specific kits and shows the shared segments in more detail than the general list. GEDmatch describes this comparison separately, as the next step after an interesting match has already been found.

If the site has a parent, an uncle or a cousin already proved, open People who match both or 1 of 2 kits. Matches shared with a parent belong to that parent’s side. That is more useful than any ethnicity calculator. Someone else’s “Baltic / Eastern European” percentage does not name a parish, and there is usually no genealogical reason to take it apart.

User Lookup by a match’s number answers a simple question: does the person have a GEDCOM and other kits on the same account. In the search, fill one field, not all of them at once. Otherwise the tool often stays silent even though the person is on the site.

Centimorgans: where to start in Polesie

The long segment first, not the sum.

GEDmatch does not set, for every population, a threshold after which a match is “real”. There is no official cutoff of 20, 15 or 10–12 cM on the site. The figures below are a practical guide for research, not a rule of the platform.

In Eastern Europe, in one parish, in Polesie, in a shtetl, a sum of centimorgans is often made of a pile of short pieces and does not prove a relationship. Look at the longest segment. It makes sense to start with those whose longest segment is from 20 cM, then come down toward 15. Anything that rests on scraps shorter than 10–12 cM usually does not lead to a document in a population like this. A threshold of 5–6 cM does not help here: it drowns the list, and the matches you could take to an archive disappear in it.

In another population and at another genealogical distance the guide can be different. What decides is not the figure by itself, but the segment together with a tree, geography and a second relative who shares that segment or does not.

A large segment still does not name the ancestor

This is an important caution.

A DNA match does not say “your shared ancestor is Ivan Petrov, born 1842”. It only says that you have a genetic match. To find a specific person you have to join several sources.

DNA match
    ↓
shared segment
    ↓
other matches, including inside the project
    ↓
family trees
    ↓
surnames and geography
    ↓
parish registers, revision lists, inventories, censuses
    ↓
shared ancestor

That is why DNA and traditional genealogy work better together. The segment suggests which branch to open. The document names the person.

When several people share a segment in the same place on a chromosome, that is called triangulation. It makes a strong research hint: the stretch may have come from one inherited ancestor. It does not become automatic proof of a specific name. It still has to be laid next to the trees and the archive.

When to buy Tier 1

GEDmatch has paid Tier 1 tools: triangulation, a search by segment, phasing and others. The site describes them as a separate set, available for a fee. You do not have to buy them straight after uploading DNA.

If you have no matches, no tree, no line you care about and no second relative to compare, a paid subscription will not create a genealogical hypothesis. The list will not grow because of it. The tools become interesting once there are already several matches with a long segment, known geography, a family tree and a specific question: not “who am I by the percentages”, but “which line is this segment from”.

If a parent is already uploaded, send the project administrator both numbers and compare matches against the parent’s kit. On the first step that separates the sides of the family and often replaces phasing, which it is still too early to pay for.

How to write to a match

Do not send a person this:

Hi. We are DNA matches. Who are you?

There will most likely be no answer. There is nothing to hold on to: no chromosome, no place, no surname.

Give context. Short, and with facts, in the person’s language. If the language is unclear, write in English:

Hello!

We have a DNA match on GEDmatch.

My kit: AB1234567
Your kit: CD7654321

We share a segment on chromosome 7,
about 28 cM.

My relevant ancestral line:
Ivan Ivanov, born around 1860,
Pinsk district, Minsk Governorate.

Surnames on this line:
Ivanov, Petrov.

Do you know your oldest ancestors from this region?
Do you have a family tree available?

Then the person has something to start a conversation from: a place, surnames and a specific segment, not a request to tell their whole biography.

And write the result down so you can come back to it:

DNA → segment → matches → shared region → surname → documents → a supposed shared ancestor.

The phrase “looks like a relative” has nothing left to check a month later.

What most often destroys the use

By this point the kit should already be filled in. If there are matches and no use, the reason is usually one of these:

  • Private or Personal Research. Other genealogists cannot use a kit like that in an ordinary search. For a project it is an empty application.
  • An alias with no surname and no place. DNA123 does not help anyone find your family.
  • One country instead of a district. Belarus is worse than Pinsk district, Minsk Governorate.
  • An application with no line. I am from Belarus does not say who your ancestor is.
  • The wrong sex. Especially awkward once the work reaches X-DNA.
  • The same DNA uploaded a second time. Ancestors do not multiply because of that.
  • A tree with no places, or a tree in which living people were exported as they are.
  • Waiting for a perfect tree. You can join with three known ancestors and good geography.

The full setup checklist is in the series overview.

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