Friday, June 10, 2016

Exogenous Ancestry – Proposing a Replacement for NPE

If I were genetic genealogy king for a day, I would replace the term “Non-Paternity Event (NPE)” with a more comprehensive term – specifically, “Exogenous Ancestry.”

Exogenous ancestry? That’s a mouthful, but what does it mean?  Well, it’s a term that I have borrowed from biological studies to explain some of the discontinuity of single source surnames with Y-DNA from outside of the family in question.  I have been contemplating for some time of using a different term from what is now commonly used in genetic genealogy – non-paternity event (NPE).

Bryan Sykes and Catherine Irven (2000) first used non-paternity event in the context of genetic genealogy to explain haplotypes that differed from the typical Y-DNA signature of a surname.  It was a borrowed term as well, as it was used in anthropology and sociology where the presumed father was not the father of a child.  Generally, this referred to infidelity on the part of the mother. 

In genetic genealogy circles, the International Society of Genetic Genealogy’s Wiki cites least 13 different categories which have been considered as non-paternity events.  While infidelity is one of these, there are other scenarios where genetic genealogists have used this moniker to describe the discontinuity between surnames and ancestry.  

What's the Beef?

The term non-paternity event and its synonyms don’t neatly fit every situation where it is used.  It assumes that the designated father (and even the child) is unaware of the child's ancestry.  This is not always the case. 

In some cases, there may not be a father in the picture and the surname traveled from mother to child.  The birth father’s name was not associated with the child and there was no “official” father from whom false paternity could be claimed.  It wouldn’t be a surname discontinuity as it continued from the mother; it would be a Y-DNA discontinuity.

In the case of complete adoptions, not only would the paternity be different, but the maternity would be as well.  Using a term such as “Exogenous Ancestry” would better fit full adoption circumstances as not only is the paternal DNA different, so is the maternal DNA.  This term would be applicable to discontinuities found in mitochondrial and autosomal DNA. 

Name changes are often considered NPEs – however, these can be voluntary and NPE doesn’t fit the situation – I am not sure any term other than “name change” would fit this scenario.

Finally, the term appears to pinpoint a given “event”; however, we may not be able to identify a specific generation when this discontinuity occurred.  While a person’s recorded ancestry may have confirmation going back several centuries, Y-DNA tells a different story.  Yes, there was some sort of misattributed paternity, but where did this “event” occur in the lineage?  Can we find it – sometimes, but not always.  We know that somewhere along the ancestral line exogenous DNA entered the picture. 

Where did this Term, Exogenous Ancestry, Originate?

It isn’t an original term, although I have been sparingly using “exogenous Y-DNA” since 2012 to soften the blow when reporting NPEs in my study. While recently performing Google searches for terminology relating to DNA from outside the family/clan/tribe, I found it used in the study of wolf and coyote populations of North America. 

Lupine biologists used it to describe DNA found in certain wolf populations that originated from outside the pack – sometimes considered an unusual occurrence.  In addition, it was also used when wolf DNA was present in populations of coyotes – especially in areas where no known wolf populations existed – hence an ancestral occurrence (von Holt, Kays, Pollinger, & Wayne, 2016).

Exogenous ancestry is broader term than non-paternity events, it is already used in mammalian DNA studies, and it is a better fit to a variety of DNA discontinuities. Will it gain in popularity?  I hope, but sometimes teaching an old dog, wolf, or coyote new tricks isn’t that easy.  I would be interested in hearing your spin on this term.


Non-Paternity Event (n.d.). International Society of Genetic Genealogy Wiki. Retrieved June 10, 2016 from

Sykes, B., & Irven, C. (2000). Surnames and the Y chromosome.  The American Journal of Human Genetics, 66(4), 1417-1419. doi:10.1086/302850

von Holt, B. M., Kays, R., Pollinger, J. P., & Wayne, R. K. (2016). Admixture mapping identifies introgressed genomic regions in North American canids. Molecular Ecology, 25(11), 2443-2453.  doi:10.1111/mec.13667