From ISOGG Wiki
Endogamy is the practice of marrying within the same ethnic, cultural, social, religious or tribal group. In endogamous populations everyone will descend from the same small gene pool. People will be related to each other in a recent genealogical timeframe on multiple ancestral pathways and the same ancestors will, therefore, appear in many different places on their pedigree chart. Endogamy can be the result of a conscious decision or cultural pressure to marry within the selected group but also occurs as a result of geographical isolation (for example, in island communities).
Examples of endogamous groups include Jews, Polynesians, Low German Mennonites, the Amish, Acadians or Cajuns (French settlers in what is now Nova Scotia, Canada), French Canadians, people from many Arab countries, people from Newfoundland and people from many islands. Endogamy is also a problem in early Colonial American populations.
The interpretation of DNA results from endogamous populations can be particularly challenging because such people will typically have large numbers of matches in the DNA databases.
The interpretation of autosomal DNA matches can be particularly difficult, especially in the case of endogamous populations where the pedigrees cannot be traced back beyond the 1800s. The relationships will often be more distant than predicted.
The Family Tree DNA Family Finder matching algorithms were modified with effect from 21st April 2011 to downweight matches between Jews in order to provide more accurate relationship predictions. 23andMe make similar adjustments for customers with Ashkenazi ancestry.
For people with Jewish ancestry it has been suggested that you need to have at least one long half-identical region of 23 cMs or more to have some hope of finding the relationship in genealogical time.
- Consangunity and endogamy resources Global Patterns & Tables of Consanguinity compiled by Bittles AH and Black ML (2014) . See in particular the map compiled by Michael Black showing Global prevalence of consanguinuity
- CousinCouples.com A website with information and resources on cousin marriages
- Dealing with endogamy, Part I: Exploring amounts of shared DNA by Paul Woodbury, LegacyTree Genealogists, 17 October 2016.
- Dealing with endogamy, Part II: Test multiple relatives by Paul Woodbury, LegacyTree Genealogists, 7 November 2016.
- FTDNA Learning Center articles on Jewish ancestry
- The polygamous town facing genetic disaster by Zaria Gorbett. BBC Future, 26 July 2017.
- Oswaks M. Tiny tombstones: inside the FLDS graveyard for babies born from incest. Broadly, 9 March 2016.
- Consanguinous marriage: keeping it in the family. The Economist, 27 February 2016.
- Mesut Erzurumluoglu M (2014). Consanguineous marriages: perspectives from social taboos, religion, and science. The Fountain 99 (May-June).
- Paull JM, Tannenbaum GS, Briskman J. Why autosomal DNA test results are significantly different for Ashkenazi Jews. AVOTAYNU Volume XXX, Number 1, Spring 2014.
- Paull JM, Tannenbaum GS, Briskman J. Differences in autosomal DNA characteristics between Jewish and non-Jewish populations. Surname DNA Journal, 24 August 2014.
- Moore CeCe. Ashkenazi Jewish DNA and the potential to piece together shattered family branches. Finding Your Roots with Henry Louis Gates, 12 November 2014.
- The surprising truth about cousins and marriage Today I Found Out: Feed Your Brain, 14 February 2014.
- Martienssen T. The island at the end of the earth. BBC Magazine, 30 December 2013. An island where everyone is related to everyone else and where most of its 62 inhabitants are descended from one man - an Englishman who settled there 150 years ago.
- Kissing cousins by Adam Huper. New Humanist, 9 September 2009.
- Can DNA testing confirm Jewish ancestry? by Bennett Greenspan. AVOTAYNU Volume XXIV, Number 1 Spring 2008.
- A tale of four DNA tests by Louis Kessler, Behold Genealogy, 21 March 2018. A comparison of DNA tests across four companies for someone of Ashkenazi ancestry.
- Rockow J. Is AncestryDNA helpful for Jewish genealogy? Ancestry.com blog, 21 July 2017.
- No, You Don’t Really Have 7,900 4th Cousins: Some DNA Basics for Those With Jewish Heritage by Jennifer Mendelsohn. Medium, 23 May 2017.
- Woodbury P. Endogamy and DNA. Guest blog post on Kitty Cooper's Blog, 25 February 2017.
- Diamond L. How endogamy looks in practice. Lara's Jewnealogy blog, 10 April 2015.
- Diamond L. My endogamous father. Lara's Family Search, 31 December 2015.
- Mondoy K. Recent founder's effect: bottlenecking and 6 Tahitian women on Pitcairn island . Hawaiian DNA blog, 21 December 2015.
- Bartlett J. Endogamy 1. Segmentology blog, 2 December 2015.
- Cooper K. Using Ashkenazi Jewish DNA to find family. Kitty Cooper's blog, 10 November 2014.
- Khan R. Ashkenazi Jews are not inbred. Gene Expression blog, 20 July 2012.
- Russell J. Endogamy and you. Really. The Legal Genealogist, 11 March 2012
- Wirth J. Inbreeding ruined these royal families. AllDay website, accessed 10 May 2016.
Videos and webinars
- Understanding DNA Results in the Context of Ashkenazi Ancestry A Family Tree DNA webinar presented by Elise Friedman
Scientific and academic papers
- Erzurumluoglu AM, Shihab HA, Rodriguez S, Gaunt TR, Day INM (2016). Importance of genetic studies in consanguineous populations for the characterization of novel human gene functions. Annals of Human Genetics. Article first published online: 22 MAR 2016
- Gauvin H, Moreau C, Lefebvre J-F et al (2014). Genome-wide patterns of identity-by-descent sharing in the French Canadian founder population. European Journal of Human Genetics 22, 814–821.
- Carmi S, Hui KY, Kochav E et al (2014). Sequencing an Ashkenazi reference panel supports population-targeted personal genomics and illuminates Jewish and European origins. Nature Communications 2014; 5: 4835. See in particular section 4.2 in the supplementary data pdf file where the authors discuss the IBD analysis.
- Ceballos FC, Álvarez G (2013). Royal dynasties as human inbreeding laboratories: the Habsburgs. Heredity 111: 114–121.
- Hamamy H (2012). Consanguineous marriages: preconception consultation in primary health care settings. Journal of Community Genetics 2012 3(3): 185-192.
- Bray SM, Mulle JG, Dodd AF et al (2010). Signatures of founder effects, admixture, and selection in the Ashkenazi Jewish population. Proceedings of the National Academy of Science USA 107(37). Epub 2010 Aug 26.
- Bittles AH, Black ML (2010). Consanguinity, human evolution and complex diseases. PNAS 107 (suppl 1): 1779-1786.
- Alvarez G, Ceballos FC, Quinterio C (2009). The role of inbreeding in the extinction of a European royal dynasty. PLoS ONE 4(4): e5174.
- Greeff JM (2007). Deconstructing Jaco: genetic heritage of an Afrikaner. Annals of Human Genetics 71: 674–688.
- Tadmouri GO, Nair P, Obeid T et al. Consanguinity and reproductive health among Arabs. Reproductive Health 2009, 6:17. doi:10.1186/1742-4755-6-17
- Snell KDM (2002). English rural societies and geographical marital endogamy, 1700–1837. The Economic History Review 55 (2): 262–298.
- Bittles AH (2001). A background summary of consanguineous marriages.
- Anderson NF (1986). Cousin marriage in Victorian England. Journal of Family History 11 (3): 285-301.
- Wikipedia page with a compilation of genetic studies of Jewish origins
- Research papers from the Clinic for Special Children, This clinic specialises in researching genetic disorders in the Amish and Mennonite communities in the US
- Canada RA. How does the nature of Jewish genealogy make autosomal DNA research more challenging. FTDNA Learning Center, 1 January 2014.
- Are you categorizing cousins differently for people with Ashkenazi ancestry? 23andMe FAQ, accessed 7 January 2015.
- Cooper K. Sticky segments. Message posted in the Rootsweb Autosomal DNA mailing list, 8 January 2015.