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More Reverse Genealogy

Last week I wrote about what reverse genealogy is and why you'd try it. Today is "Backwards Day" so I'm covering how to research backwards (as in forwards, wait... what?)
Reverse genealogy is great for cluster research, genetic genealogy, and even tough adoption cases. | The Occasional Genealogist

To recap, reverse genealogy is researching from the past to the present, the opposite direction, or backwards, from what we normally do.

Last week I mentioned some uses for genetic genealogy and traditional genealogy as well as cases where non-genealogists might want to try reverse genealogy. How to go from the past to the present is easiest to understand with traditional genealogy so I'll start there and then move to harder situations.

Traditional Genealogy

Genealogy always begins with the known and moves to the unknown. With a traditional genealogy example, it's pretty easy to see how you'd start from the known past and work to the unknown living. You'd start with the ancestor you're trying to confirm (or the oldest ancestor you have confirmed) and research their descendants instead of their ancestors. There is no difference in how you do the research.

If you recall, a great use of reverse genealogy for non-DNA examples is to increase your research cluster for cluster genealogy or using the "FAN principal." Your interest is a traditional genealogy goal, for example, identifying an ancestor. When you get stuck identifying them, you can try identifying their descendants to broaden your available records.

How to do reverse genealogy in this simple example is pretty simple in itself. Instead of researching ancestors, you expand collaterally (siblings and if known, cousins, aunts, uncles, etc.) and then move towards more recent generations by researching the descendants of those people.

If you aren't familiar with the concept of collateral or cluster research, the purpose is to identify additional records (because those you've used haven't answered your question). For very difficult problem, you may need to mainly do cluster research with an ever expanding cluster.

Often it isn't possible to expand the cluster back in time so you research people in the generation you already know or their descendants (and their descendants, etc.), hence the need for reverse genealogy.

You can take this as far as you find helpful (or interesting, hey, it's your hobby, interesting is a good motivation).

That's pretty straight forward, or backward (or is it forward...).

Genetic Genealogy


Verifying and Pre-finding Lineages

Next, what if you're doing genetic genealogy? Reverse genealogy is a must when using DNA. Hopefully, you already understand you need to supplement DNA results with traditional genealogy.

You need to correctly identify the ancestry of the test taker. That's not enough, though. For a match to be helpful, you need to also correctly identify the match's ancestry. Reverse genealogy can speed this up.

If you're working on a DNA project which focuses on using DNA for a specific genealogical goal, you can go ahead and do reverse genealogy on your ancestor of interest. Instead of going back in time, look for his/her descendants. This is what I'm calling "pre-finding lineages." You find the lineage (i.e. research it) before you have a match.

This is the most basic reverse genealogy. It's useful for genetic genealogy. Your DNA project will give you your goal. That goal is no different than the goal of someone writing a family history of all the descendants of a certain person. Don't let the fact it's an idea wrapped up with the "new" science of DNA make you think it's something unusual or particularly difficult.

Why would you spend your time "pre-finding" lineages? Why not just wait for the matches with a tree?

Not everyone has the same research skills. If you make sure you identify the correct descendants, as far as you can, you will find you have part of the tree done for some matches. Of course, you don't know where to focus if you just do reverse genealogy without having a particular match or matches to direct you, but that's OK.

Researching descendants for a DNA project, without focusing on specific matches, is just like doing reverse genealogy for cluster research. For me, this is a great reason to do reverse genealogy, it can serve two purposes, traditional and genetic, without even focusing on specific DNA matches.

Reverse genealogy can have several uses in genetic genealogy so let's look at another use.

Finding Test Takers

You might do reverse genealogy on your known ancestor or the family of a DNA match, looking for others to test, to see if they also match the focus test.

You may be looking for options to use a different type of test (this is often done to find a male to use Y-DNA but can also apply to mtDNA). Reverse genealogy is the way to find new testees outside your known relatives.

Identifying Possible Parents

I've done reverse genealogy on DNA matches, looking for a possible mystery parent. This is a harder "how would I use reverse genealogy?" scenario to explain.

If there are few enough generations between an identified shared ancestor and the testee, it's possible to identify all the known descendants. This is nearly impossible if there are too many generations because the parental options become too numerous to be useful. It is a somewhat personal choice about what is "too many," though.

To be clear, you may have a group of matches that share an ancestor. You (or whoever has the unknown ancestor) do not have that ancestor/couple in your known tree. If you have no other identifiable shared ancestor with the matches in the group, it's reasonable to see if the ancestor the group of matches shares can fit into your tree.

Most likely you can already imagine how to use reverse genealogy if you've done DNA analysis that gives you a narrow focus. If you've done DNA analysis (not just analysis of trees but of chromosomes), you have a clear direction to work towards.

I've used this technique when I haven't been able to do DNA analysis. This often happens because matches are only at AncestryDNA and the only information I have is a tree, no segment information such as you could get from FTDNA or GEDMatch.

If traditional research is your only choice, reverse genealogy is what you will need to do. In one specific case, I identified the closest matches who shared an ancestor with each other but not with the target test. It was possible the match was through the mystery parent (actually parents).

Without segment information, I couldn't be sure of anything, but the matches weren't responding so I wasn't getting more DNA information anytime soon, if ever. Based on the information I did have, it was possible the ancestor shared by that group of matches could be the grandparent or great-grandparent of one of the mystery parents I was seeking.

I would not have tried this technique if it seemed like the shared ancestor should be much farther back. That would not have been a good use of my time. Based on the shared amount of DNA, the number of generations is still an estimate so the true shared ancestor (the Most Recent Common Ancestor, MRCA) could easily be two generations farther back.

There were multiple factors that made it reasonable to try researching two generations of descendants to see if there was someone who fit the criteria for the mystery parent I was seeking. You have to judge those factors in your project.

This was not in my family. I don't often use this technique in my family unless I have an EXCELLENT lead on a possible MRCA. My entire family is from Georgia so geography is pretty much useless as a criteria. Geography (or ethnicity, which is a variation of geography in many U.S. cases) is one of the easier ways to choose who to research or not, assuming all your ancestors aren't from one state like mine.

[Reverse genealogy has not solved this problem but so far it does appear I'm on the right track. Without more information, including new matches or segment data, I can't determine more.

Update: After re-reviewing the reverse genealogy work, it appears a parent has been found. There appears to be only one reasonable option. This still isn't solved but the next steps, if more matches or segment information doesn't become available, is to determine what additional research can make this "solved." This is a matter of satisfying the genealogical proof standard by performing reasonably exhaustive research.

This would have been impossible without reverse genealogy. Even with more DNA data, it probably wouldn't have gotten anywhere without large amounts of reverse genealogy. DNA plus reverse genealogy is a powerhouse.]

Reverse Genealogy for Non-genealogists

Finally, what if you're not a genealogist and you have an unknown parent (whether your own or a few generations back)? How can reverse genealogy help? There are essentially two ways.

The first is if you know of any other relatives. This is the same as doing cluster research. You're looking for information not just in the direct line, but by branching out into every other relative you can identify.

I'm always amazed how I will do a little collateral research and it doesn't seem to be going anywhere. Later I will do more (because other avenues are going nowhere). When I do more reverse genealogy, I often find just what I need. The problem is you don't know in which collateral relative's records or how far down the line (in the collateral's records, or his/her children, or their children, even).

If you aren't a genealogist and you're looking for an unknown parent or grandparent, don't just try genealogy. Reverse genealogy, when you have clues to collateral relatives, is often much easier than researching your actual mystery. It is a mystery after all!

If you don't have any other relatives, you may do reverse genealogy on anyone you can associate with the mystery parent. This can be difficult but it's better than having no one to research at all.

As an example, someone once asked me about a grandparent that died at Pearl Harbor. They knew nothing about the grandparent to learn more about that branch of the family. The obvious fact they knew was the military service.

Military service is obviously a buffet of additional people. If the unit is known, you can learn about the average soldier in that unit (do many of them come from the same place? were they stationed somewhere else where additional records might exist---particularly if this is where a couple met or is known to have lived).

If you can narrow down to focus on other soldiers, especially if you can identify a connection to your person, you can research them. This may start as traditional research and then turn to reverse genealogy to find more stories or even living people to talk to.

If the service is unknown, you atleast have a lot of people to consider. Hopefully you're not looking for John Smith! By using reverse genealogy, you can exclude people that have characteristics that exclude them from being your person.

This could be a physical description (perhaps grandmother talks about his blonde hair or maybe his dark eyes, or how very tall he was---something concrete). Perhaps you can exclude people that lived. Being alive or dead at a certain time is an identifying characteristic. Age is not a good characteristic for military research unless you have something unusual. The average soldier falls in an average age range and people do lie about their age (to their girlfriend or the enlistment officer!).

Non-genealogists are often dealing with an adoption. That's one of the few reasons people do intense research on someone without being a genealogist.

In an adoption case, you might have non-identifying information. You might do reverse genealogy on a candidate to gather information of the same type to compare. It might be necessary to research a generation or two towards the present to find that information even if it is about the candidate.

In other cases, you may have a family story describing the mystery parent. You might do reverse genealogy to try and gather the same type of information for comparison.

Examples of types of information could be an occupation, maybe a musician (but not a farmer if you're looking in a rural area!). Perhaps the person went to college, no point in continuing reverse genealogy on someone who clearly did not. What about an ethnicity or a residence. I have an illigitimacy in my recent family history where I was told, "he was from [a town in another county]" (and I have a name although not much else!). Socio-economic status might help (if they didn't lie).

These are all characteristics you could learn about someone using reverse genealogy. For non-genealogists, cases often require excluding people as much as including them.

Reverse Genealogy: Does It Answer Your Question?

"How" you use reverse genealogy might not be to provide a concrete answer. It's still a helpful technique for many different types of problems.

You may have been doing it already, not even thinking about researching descendants as anything different from ancestors. That's great. Now you know it has a name in case you need to learn more.

If you've never considered researching descendants, now you can.

Reverse genealogy is really a must for genetic genealogy, regardless of your goal. If nothing else, you can identify people to test. You may also be able to exclude candidates, prioritize research, or simply increase the records you can use. Much of this applies to genetic genealogy and traditional genealogy.

How do you do reverse genealogy? Just like "genealogy." You start with what you know and move to the unknown.


Solve a family mystery with reverse genealogy. Some problems start in the past and you need to research to the present for a solution. | The Occasional Genealogist


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