Non-paternity event is a term in genetic genealogy and clinical genetics to describe instances in which the biological father of a child is someone other than who it is presumed to be. The presumption may be either on the part of the presumed father or by the physician. Non-paternity may result from a number of different scenarios: it may arise from sperm donation or when the mother had sexual intercourse with a man other than the presumed father. Other than the situations of gestational surrogacy and chimerism, the identity of a child's mother is seldom in doubt. Non-paternity (and non-maternity) may also result from hidden adoptions: that is, when a child is never told he or she was adopted. Where there is uncertainty, then the only definitive diagnosis of non-paternity is from DNA testing.
The discovery of previously unsuspected or undisclosed non-paternity may have both social and medical consequences. Non-paternity that is due to a previously undisclosed extra-marital relationship often has serious consequences for a marital relationship. Non-paternity is medically relevant when interpreting the results and utility of genetic screening for hereditary illnesses such as cystic fibrosis.
In genetic genealogy the term NPE is often used in a wider context to indicate a break in the link between the Y-chromosome and the surname. Such a breakage may occur because of formal or informal adoption, illegitimacy inside ("extramarital event"/infidelity or rape) or outside of marriage, child known by other surname (mother's maiden name, stepfather's name), the use of an alias or a deliberate change of surname.
Testing for non-paternity
The only definitive test for paternity is DNA testing. Requirements for consent and counselling for DNA testing vary by country. Sons can be tested by Y-DNA and atDNA, daughters by atDNA and X-DNA.
Rates of non-paternity
However, a 2005 scientific review of international published studies of paternal discrepancy found a range in incidence from 0.8% to 30% (median 3.7%), suggesting that the widely quoted figure of 10% of non-paternal events is an overestimate. In situations where disputed parentage was the reason for the paternity testing, there were higher levels; an incidence of 17% to 33% (median of 26.9%). Most at risk of parental discrepancy were those born to younger parents, to unmarried couples and those of lower socio-economic status, or from certain cultural groups.
A 2006 study examined non-paternity rates from 67 published studies. Non-paternity rates for men who were judged to have high paternity confidence ranged from 1.9% in the U.S. and Canada, 1.6% in Europe, and 2.9% elsewhere. In contrast, men in studies of disputed paternity, considered to have low paternity confidence, the rates of non-paternity were higher – 29% in the U.S. and Canada, 29% in Europe, and 30% elsewhere.
The rates value varies according to the population studied:
- United Kingdom:
- Mexico: 9.8% to 13.8% in a sample of 396 children
- Switzerland: 0.3 to 1.3% in a sample of 1,607 children
- United States:
- France: 2.8% in a sample of 362 children
- Macintyre S & Sooman A (1991). "Non-paternity and prenatal genetic screening". Lancet 338 (8771): 869–871. doi:10.1016/0140-6736(91)91513-T. PMID 1681226.
- Georgia K. Bopp, Non-Paternal Event (NPE), Dec. 2006, URL Aug. 2012: http://freepages.genealogy.rootsweb.ancestry.com/~gkbopp/DNA/falsepaternal.htm
- Neale MC; Neale BM; Sullivan PF (2002). "Nonpaternity in Linkage Studies of Extremely Discordant Sib Pairs". Am J Hum Genet 70 (2): 526–529. doi:10.1086/338687. PMC 384925. PMID 11745068.
- Rincon P (11 February 2009). "Study debunks illegitimacy 'myth'". BBC News. Retrieved 11 February 2009.
- Bellis MA; Hughes K; Hughes S; Ashton JR (September 2005). "Measuring paternal discrepancy and its public health consequences". J Epidemiol Community Health 59 (9): 749–54. doi:10.1136/jech.2005.036517. PMC 1733152. PMID 16100312.
- Anderson, K. G. (2006) Evidence from Worldwide Nonpaternity Rates. Current Anthropology, 47, 3 pp. 513-520. http://www.journals.uchicago.edu/doi/abs/10.1086/504167
- King TE & Jobling MA (2009). "Founders, Drift, and Infidelity: The Relationship between Y Chromosome Diversity and Patrilineal Surnames". Mol Biol Evol 26 (5): 1093–102. doi:10.1093/molbev/msp022. PMC 2668828. PMID 19204044.
- Sykes, Bryan; Irven, Catherine (2000). "Surnames and the Y Chromosome". The American Journal of Human Genetics 66 (4): 1417–1419. doi:10.1086/302850. PMC 1288207. PMID 10739766.
- Cerda-Flores RM; Barton SA; Marty-Gonzalez LF; Rivas F; Chakraborty R (1999). "Estimation of nonpaternity in the Mexican population of Nuevo Leon: A validation study with blood group markers". Am J Physical Anthropol 109 (3): 281–293. doi:10.1002/(SICI)1096-8644(199907)109:3<281::AID-AJPA1>3.0.CO;2-3. PMID 10407460.
- Sasse G; Müller H; Chakraborty R; Ott J (1994). "Estimating the frequency of nonpaternity in Switzerland". Hum Hered 44 (6): 337–43. doi:10.1159/000154241. PMID 7860087.
- Schacht LE; Gershowitz H (1963). "Frequency of extra-marital children as determined by blood groups". In Gedda L. Proceedings of the Second International Congress on Human Genetics (Rome, Sept 6–12, 1961). Rome: G Mendel. pp. 894–97.
- Ashton GC (1980). "Mismatches in genetic markers in a large family study". Am J Hum Genet 32 (4): 601–13. PMC 1686125. PMID 6930820.
- Le Roux, Marie-Gaelle; Pascal, Olivier; Andre, Marie-Therese; Herbert, Odile; David, Albert; Moisan, Jean-Paul (1992). "Non-paternity and genetic counselling". The Lancet 340 (8819): 607. doi:10.1016/0140-6736(92)92139-7.
- "NPE's and Their Resolution: Y-DNA Testing for Genealogy and the Resolution of Unexpected Results"., including case studies