Concepts – Endogamy and DNA Segments

Members of endogamous populations intermarry for generations, creating many segments that match, especially at small centiMorgan levels. These matching segments occur because they are members of the same population – not because they are genealogically related in a recent or genealogical time-frame.

Said another way, endogamous people are all related to each other in some way because they descend from a small original population whose descendants continued to intermarry without introducing people outside of the community into the genetic line. In other words, the DNA segments of the original population simply keep getting passed around, because there are no new segments being introduced.

If you only have 10 segments at a specific genetic location to begin with, in the original population – then the descendants of those original people can only have some combination of the DNA of those original people until another person is introduced into the mix.

Examples of endogamous populations are Ashkenazi Jews, Native Americans, Acadians, Mennonite, Amish and so forth.

If you have some family lines from an endogamous population, you’ll match with many members of that group. If you are fully endogamous, you will have significantly more matches than people from non-endogamous groups.

I suggest that you read my article, Concepts: The Faces of Endogamy to set the stage for this article.

In this article, I want to provide you with a visual example of what endogamy looks like in a chromosome browser. It doesn’t matter which vendor you use so long as you can drop the cM count to 1, so I’m using FamilyTreeDNA for this example.

I’ve used three people as examples:

  • Non-endogamous European
  • Ashkenazi Jewish
  • Native American (Sioux)

For all testers, I selected their closest match above 200 cM total plus the following 4 for a total of 5 people to compare in the chromosome browser. I have only shown chromosomes 1-8 because I’m trying to convey the concept, not exact details of each chromosome, and 8 chromosomes fit into one screen shot.

If you’re not familiar with the terminology, you can read about cM, centiMorgans, in the article “Concepts – CentiMorgans, SNPs, and Pickin’Crab.”

Let’s take a look at our 3 examples, one at a time.

Non-Endogamous European Individual

The tester is non-endogamous. Four of the 5 individuals are known family members, although none were target tested by the tester.

Endogamy non-endogamous.png

The tester’s matches at 1 cM are shown below:

Endogamy non-endogamous 1cM.png

Note that the grey hashed regions are regions not reported, so no one matches there.

Below, the same 5 matches shown at 7 cM where roughly half of the matches will be identical by chance. Identical by descent segments include identical by population. You can read about the various types of “identical by” segments in the article, “Concepts – Identical by…Descent, State, Population and Chance”.

Endogamy non-endogamous 7cM.png

Ashkenazi Jewish Individual

The tester, along with both of their parents have tested. None of the matches are known or identified relatives.

Endogamy Jewish.png

Even though none of these individuals can be identified, two are related on both sides, maternal and paternal, of the person who tested.

In the chromosome browser, at 1cM, we see the following:

Endogamy Jewish 1cM.png

At 7cM, the following:

Endogamy 7cM.png

Native American Individual

The tester is 15/16 Native from the Sioux tribe. It’s unlikely that their matches are entirely Native, meaning they are not entirely endogamous. None of the matches are known or identified family members.

Endogamy Native.png

At 1 cM shown below:

Endogamy Native 1cM.png

At 7 cM, below:

Endogamy Native 7cM.png

Side by Side

I’ve placed the three 1 cM charts side by side with the non-endogamous to the left, the Jewish in the center and the Native, at right.

endogamy side by side.png

It’s easy to see that the Jewish tester has more 1 cM segments than the non-endogamous tester, and the Native tester more than both of the others.

Summary Comparison Chart

The chart below shows the difference in total number of segments, number of segments between 1 and 6.99 cM, and number of segments at 7 cM or larger. I downloaded these results into a spreadsheet and counted the rows.

Total Segments Total segments at 1 – 6.99 cM Total at 7 or > cM % 7 or >
Non-Endogamous 98 70 28 29
Jewish 168 139 29 17
Native American 310 295 15 5

You’ll note that the non-endogamous individual only has 58% of the number of total segments compared to the Jewish individual, and 32% compared to the Native American individual. The Jewish individual has 54% of the number of segments that the Native person has.

I was initially surprised by the magnitude of this difference, but after thinking about it, I realized that the Native people have been endogamous for a lot longer in the Americas than the Ashkenazi Jewish people in Europe. At least 12,000 years compared to roughly 2000 years, or approximately (at least) 6 times longer. Furthermore, the Native people in the Americans were entirely isolated until the 1400s, with no possibility of outside admixture. Isolation lasted even longer in the tribes that were not coastal, such as the Sioux in the Dakotas.

Note that the Jewish person and non-endogamous person have almost as many 7cM segments as each other, but the Native person has roughly half as many when compared to the other two. That means that because I made my selection starting point based on total cM, and the Native person has a LOT more 1-6.99 cM segments than the others, at that level, there are fewer strong segment matches for the Native individual.

The Native person’s percentage of 7 cM or greater segments is a much smaller percentage of the total segments.

As a percentage, the 7 or greater cM segments are 29% of the non-endogamous person’s total, 17% of the Jewish person’s, but only 5% of the Native person’s total.

Endogamy not only makes a difference when comparing results, but the specific endogamous population along with their history, how heavily endogamous they are, and how long they have been endogamous appears to factor heavily into the comparison as well.

DNA Testing and Transfers – What’s Your Strategy?

The landscape of genetic genealogy is forever morphing.

I’m providing a quick update as to which vendors support file transfers from which other vendors in a handy matrix.

Come join in the fun!

Testing and Transfer Strategy

Using the following chart, you can easily plan a testing and transfer strategy.

DNA Vendor Transfer Chart 2019

Click on image to enlarge.

Caveats and footnotes as follows:

1. After May 2016, the Ancestry test is only partly compatible, meaning you receive your closest matches (about 20-25% of the total) but won’t receive distant matches due to chip incompatibility. However, beginning in April 2019, when Family Tree DNA implemented the Illumina GSA chip, Ancestry files are receiving all matches.

2. The 23andMe December 2010 (V3) version is fully compatible. December 2013-August 2017 (V4) and August 2017 (V5) tests are partly compatible meaning you receive your closest matches (about 20-25% of the total) but won’t receive distant matches due to chip incompatibility. However, beginning in April 2019, when Family Tree DNA implemented the Illumina GSA chip, 23andMe V4 and V5 files are receiving all matches.
3. GedMatch has been working to resolve autosomal matching issues between vendor’s chips. Patience is a key word.
4. LivingDNA does not yet have full blown matching (I have one match), which has been in the testing phase for months, and has recently changed chip vendors.
5. Customer must extract the file using a file utility before it can be uploaded. LivingDNA indicates that they are working on a simpler solution.
6. Files transferred to LivingDNA must be in build 37 format.
4-12-2019 update – please note that MyHeritage does not accept 23andMe V2 files, only V3, V4 and V5.

Recommendations

My recommendations are as follows, and why:

Transfer Costs

Autosomal transfers and matching are free at the vendors who accept transfers, but payment for advanced tools is required.

  • Family Tree DNA – $19 one-time unlock fee for advanced tools
  • MyHeritage – $29 one-time fee for advanced tools
  • GedMatch – many tools free, but for Tier 1 advanced tools, $10 per month

All great values!

Please note that as vendors change testing chips and file formats, other vendors who accept transfers will need time to adapt. I know it’s frustrating sometimes, but it’s a sign that technology is moving forward. The good news is that after the wait, if there is one, you’ll have a brand new group of genealogy matches – many holding clues for you to decipher.

I’m in all of the databases, so see you there.

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Disclosure

I receive a small contribution when you click on some (but not all) of the links to vendors in my articles. This does NOT increase the price you pay but helps me to keep the lights on and this informational blog free for everyone. Please click on the links in the articles or to the vendors below if you are purchasing products or DNA testing.

Thank you so much.

DNA Purchases and Free Transfers

Genealogy Services

Genealogy Research

Top DNA Articles for 2018

2018 Top 10

It’s always interesting to look at the most popular articles at DNA-Explained at the end of each year. Out of millions of page views, these are the Top 10 in 2018, with the * indicating articles that were in the 2017 Top 10 list as well. If you missed some, now’s a good time to catch up or to share with friends.

*Proving Native American Ancestry Using DNA
*Concepts – Calculating Ethnicity Percentages
*Which DNA Test is Best?
Ancestral DNA Percentages – How Much of Them is in You?
*Ethnicity Testing – A Conundrum
*How Much Indian Do I Have in Me?
Autosomal DNA Transfers – Which Companies Accept Which Tests?
Concepts – Percentage of Ancestors’ DNA
X Marks the Spot
*Mythbusting – Women, Fathers and DNA

Spread the Word – What You Can do to Help!

The purpose of writing articles is to educate people who have taken genetic genealogy tests along with providing motivation for potential testers.

With more and more companies performing tests, and record numbers of people testing – there’s a lot of confusion and misinformation out there.

You can help by spreading the word.

If you see a question and know that I wrote about that topic, you can enter key words into the search box at the top of any blog page to find the article.

You can always share the links to articles on social media, with friends and at genealogy meetings. If you want to share the actual text of the article in more than a summary fashion or relatively short excerpts (with attribution), as in a reprint, please check with me first – but as for links – please share away. You don’t need to ask first. Sharing is the purpose of writing these articles.

Educating others with credible information helps all of us have a better experience.

What Would You Like in 2019?

To some extent, I maintain a list of articles that I’d like to write at any given point in time. My candidate list always seems to be longer than the time I have, but I do try to prioritize the topics based on, in no particular order:

  • Discoveries in my research
  • Industry happenings
  • The need
  • Reader requests

So, given that criteria, what topics would you like to see me cover in 2019? I’m also open to suggestions during the year as well. In fact, this article is in response to a reader’s “wish.”

Please post your suggestions in the comments. I’d love to hear from you!

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Disclosure

I receive a small contribution when you click on some (but not all) of the links to vendors in my articles. This does NOT increase the price you pay but helps me to keep the lights on and this informational blog free for everyone. Please click on the links in the articles or to the vendors below if you are purchasing products or DNA testing.

Thank you so much.

DNA Purchases and Free Transfers

Genealogy Services

Genealogy Research