Endogamy is the practice of intermarrying within a defined community. Genetic genealogy focuses on the genetic effects of prolonged endogamy: when a community marries within its defined culture or location for many, many generations.
There are many different kinds of endogamous communities. Geographical isolation creates endogamous communities: those that lived on an island, or in a mountainous region, or anywhere without much incoming traffic. Cultural boundaries, whether religious, tribal, language, ethnic, or socio-economic, can also lead to endogamy.
When a family tree includes endogamy, it can be confusing to sort out all the identities and relationships. DNA analysis can be complicated, too. An endogamous community produces descendants who share DNA with each other based not on one recent common ancestor or ancestral couple, but because of the high degree of intermarriage over time.
What’s the difference between endogamy, multiple relationships, pedigree collapse and founder effect?
All of these situations on a family tree–endogamy, multiple relationships, pedigree collapse, and founder effect–can affect how much DNA is shared with matches.
- Multiple relationships is when two people are related to each other in more than one way. For example, if two brothers marry two sisters, any descendants will be related to each other through both the mother and the father.
- Pedigree collapse is when two genetically-related people have children together (like first-cousin or second-cousin marriages). This was quite common in the past, and still is in some cultures. The result for a family tree is that it “collapses” at the top. Instead of getting ever-wider as it goes back in time, the same ancestral couples appear multiple times over. When this happens over and over again, endogamy can result.
- Founder effect is when an entire community is established by just a few people, or a small “founder population.” There would be less genetic diversity in the descendants of that community. For endogamy to come into play as well, that community would have to stay genetically isolated for a long time.
How can I tell if my family tree is endogamous?
People who are already familiar enough with their family’s background may already know whether they descend from an endogamous community. Endogamy is well-recognized among Ashkenazi Jews, Pacific Islanders, Acadians/Cajuns, Amish and some Mennonites, New Foundlanders, and parts of India and the Arab world. Sometimes people know from research or family lore that their family came from a place or a population where endogamy might be likely. It’s possible to find these clues by doing genealogy and by looking at Genetic Groups in MyHeritage DNA test results.
If the effects of endogamy are visible in a person’s DNA, their MyHeritage DNA match list will have clues for you. Here are two of the most important:
- Overlapping DNA match groups. DNA matches should be sortable into distinct groups representing each family line (sort matches by following the instructions here or using MyHeritage’s AutoClusters tool). If groups overlap significantly, that may be a sign of endogamy (or multiple relationships, or pedigree collapse, which genealogy research should be able to help identify; here’s how to correct for pedigree collapse when working with DNA matches).
- Longest shared segment. For each DNA match on the list, MyHeritage provides not just how much total DNA is shared, but the size of the longest intact shared piece of DNA. A longer intact piece of shared DNA usually indicates closer genetic relationships than the same total amount of DNA added up from lots of little tiny pieces that result from endogamy. If the largest shared piece of DNA is less than 20 cM, it is unlikely two people share a recent common ancestor.
For those with Ashkenazi Jewish heritage in their DNA ethnicity results, MyHeritage does a little extra work when calculating DNA matches. A larger initial piece of DNA is required to be shared between two people who have at least 50% Ashkenazi Jewish ancestry before they are considered a true match. This is a helpful adjustment.
What should I do with my endogamous DNA match list?
Those with endogamy on their DNA match list should start by focusing on individual matches instead of trying to group matches into discrete lineages. They should start with Best Mystery Matches, a term used and explained in detail in Your DNA Guide–the Book. Best Mystery Matches have a long shared DNA segment and have a family tree posted. They should use the predicted relationship provided by MyHeritage to estimate the Generation of Connection: that spot in a match’s family tree where they connect. For example, if MyHeritage predicts a third cousin relationship between two matches, it is likely they share a 2X great grandparent couple. The next step would be to do genealogy to identify as many of this match’s eight 2X great grandparents as possible to find the connection.
See more
Explore more about endogamy
- Endogamous Communities and their DNA Fingerprints
- Founder Effect: DNA and Endogamy
- How to Research Your Jewish Ancestors on MyHeritage
- Pedigree Collapse v. Endogamy
- MyHeritage DNA at MyHeritage
- Ethnicities around the world at MyHeritage
- What Is My Ethnicity? How MyHeritage Estimates Ethnicities at MyHeritage Knowledge Base
- Where's My Ethnicity?!: Why An Ethnicity Might Not Show Up In Your DNA (and How To Find Evidence Of It Anyway) at MyHeritage Knowledge Base
References