Non-paternity event is a term in genetic genealogy and clinical genetics to describe the case where 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 situation of egg donation, 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 will have obvious consequences for the marital relationship which it violates. 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 with the Y-chromosome and the surname. Such a breakage may occur because of illegitimacy, the use of an alias, or a deliberate change of surname.
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 rate of non-paternity varies according to the population studied:
- Mexico: 9.8% to 13.8% in a sample of 396 children.
- Switzerland: 0.3% to 1.3%.
- United Kingdom: 1 to 2% in a sample of 1,678 men.
- United States: A study in Michigan of 1417 white and 523 black children found non-paternity rates of 1.4% and 10.1% respectively.
- Neale MC, Neale BM, Sullivan PF. Nonpaternity in linkage studies of extremely discordant sib pairs. Am J Hum Genet, 2002, volume 70, issue 2, pp526-529.
- Rincon P. Study debunks illegitimacy 'myth'. BBC News, 11 February 2009.
- Bellis MA, Hughes K, Hughes S, Ashton JR. Measuring paternal discrepancy and its public health consequences. Journal of Epidemiology and Community Health. September 2005; 59, 9: 749–54.
- Anderson, K. G. (2006) Evidence from Worldwide Nonpaternity Rates. Current Anthropology, 47, 3 pp. 513-520.
- Cerda-Flores RM, Barton SA, Marty-Gonzalez LF, Rivas F, Chakraborty R. Estimation of nonpaternity in the Mexican population of Nuevo Leon: A validation study with blood group markers. Am J Physical Anthropol, 1999, volume 109, issue 3, pp281-293.
- Sasse G, Müller H, Chakraborty R, Ott J. Estimating the frequency of nonpaternity in Switzerland. Hum Hered, 1994, volume 44, issue=6, pp337-343.
- King TE and Jobling MA. Founders, drift and infidelity: the relationship between Y chromosome diversity and patrilineal surnames. Mol Biol Evol, 2009, volume 26, issue 5, pp1093–102
- Schacht LE, Gershowitz H. Frequency of extra-marital children as determined by blood groups. In: Gedda L (ed). Proceedings of the Second International Congress on Human Genetics Rome, Sept 6-12, 1961.
- G Mendel, 1963, pp 894-897.
- A study of 1748 Hawaiian families with 2,839 children reported a non-paternity rate of 2 to 3%.
- Ashton GC. Mismatches in genetic markers in a large family study. Am J Hum Genet. 1980, volume 32, pp601-613.
- Non-paternity events in genetic genealogy
- Wikipedia article on misattributed paternity
- Wikipedia article on Paternity fraud
- A review of the published literature by Child Support Analysis
- Weblog providing past and current examples of NPEs
- Diana Gale-Mathieson: NPE's and Their Resolution (a perspective from an American genetic genealogist)
- A non-paternity event calculator An Excel spreadsheet program created by Robert Tarin that determines the chances of a non-paternity event affecting the certainty of a paper-trail genealogy in a given number of generations. The program allows for the input of different non-paternity rates for a population as well as number of generations.
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