Just How Common is Paternity Surprise?

paternity surpriseBBC News and other media are reporting how a recent DNA test result reveals that the Archbishop of Canterbury was not fathered by whom he believed had been his dad.

The Most Reverend Justin Welby, 60, is reported to have said that the identity of his real biological father has come as a “complete surprise.” The Archbishop has now found out that he is, in fact, the son of Sir Winston Churchill’s last private secretary, the late Sir Anthony Montague Browne.

Before the DNA test Justin Welby had considered his father to have been a whiskey salesman named Gavin Welby, who died in 1977.

His mother, Lady Williams of Elvel, has now also confirmed, according to the BBC News website, that she had a “liaison” with Sir Anthony just before she married in 1955.

This news might add to the widespread belief, fueled by the kind of paternity tests that have become referred to in gossip magazines, talk shows and ‘trailer trash’ TV, that many fathers are deceived into raising children who are not theirs genetically.

Extra-Pair Paternity

The common urban myth is that there are extraordinarily high rates of what geneticists refer to as ‘extra-pair paternity,’ or EPP. Quotations of estimates typically range from 10–30%.

Perhaps one reason for these high estimations is that female adultery is supposedly common, occurring in an estimated 5–27% for people younger than 30 years old, depending on which survey you consider.

Some evolutionary biologists and psychologists even speculate that some females may also be driven biologically, through evolutionary selection pressures, to actively seek ‘extra-pair copulations.’ This might be a way to improve the genetic diversity and biological quality of offspring, argue evolutionary biologists and could be an insurance against male infertility.

Another evolutionary psychology theory is that extra-pair copulations allow women to have the best of both worlds. They obtain the benefits of parenting and fathering from more reliable domestic ‘safe’ types of male, even as they bear the genes of a child fathered by more exciting ‘alpha-male’ ‘hunter’ types.

But now a new investigation and review of the academic area, by scientists at the University of Leuven, Belgium, and the Department of Genetics, University of Leicester, is arguing that ‘extra-pair paternity’ in contemporary human populations is only 1–2%.

The study, by Maarten Larmuseau, Koen Matthijs and Tom Wenseleers, contends that the previously inflated figures are not representative of the general population, partly because they were mainly based on data from paternity testing laboratories where paternity was disputed.

Critics, however, of these lower recent estimates from genetic techniques, which  have only become available over the past decade, point out that in historical times, ‘extra-pair paternity’ rates might well have been much higher, because of the lack of reliable contraception.

The era when the Archbishop of Canterbury’s mother had that “liaison,” was back in 1955.

The authors of this new investigation, entitled ‘Cuckolded Fathers Rare in Human Populations’, due to be published shortly in the academic journal, Trends in Ecology & Evolution, quote another recent study that did find a slight but significant decrease in ‘extra-pair paternity’ events following the introduction of the birth control pill.

To test this idea, several recent studies have developed new approaches that enable ‘extra-pair paternity’ rates from several centuries ago, before modern contraception, to be estimated.

To be able to reconstruct the sex lives of our ancestors and infer extra-pair paternity rates as they would have been in historical times, one new genetic technique compares family specific Y chromosomal variation between men, with genealogical evidence of paternity.

In this ‘genealogical pair’ method, ‘extra-pair paternity’ events show up in mismatches in the paternally inherited Y chromosomes.

Other indirect approaches have also been developed that provide estimates of past ‘extra-pair paternity’ rates by analyzing the association between Y chromosomal variation and paternally inherited surnames.

Using this first method, historical ‘extra-paternity’ rates were estimated at just 1.8% in Mali. This low estimate was surprising, given that the study got its data from word of mouth, which by itself could have contributed to error.

Written Evidence

Subsequently, another study further perfected the genealogical pair method, employing written genealogical evidence, and also introduced the other method to provide an independent estimate, and applied it to a Western population in Flanders, Belgium.

This study arrived at a similarly astonishingly low ‘extra-pair paternity’ estimate of 0.9% per generation over the past 500 years.

Finally, three further studies have now appeared, according to Maarten Larmuseau, Koen Matthijs and Tom Wenseleers, that all confirm these very low occurrences of human ‘extra-pair paternity’ among several other Western populations: 0.9% per generation over the past 300 years in a (Western) Afrikaner population in South Africa, 1.2% per generation over the past 400 years in a north Italian population, and 0.6–1.7% per generation over the past few centuries in Catalonia.

The surprising conclusion from these new studies, according to Larmuseau, Koen Matthijs and Wenseleers, is that human ‘extra-pair paternity’ rates have stayed near constant at around 1% (maximally 2%) across several human societies over the past several hundred years.

If you hypothesize that contraception was more difficult or unreliable in the past, given modern rates of adultery, and if you project these rates back into history, you would have expected much higher rates of ‘extra-pair paternity’ to show up in this genetic testing.

Theoretically high adultery rates would be more likely to be revealed in the genes passed on in past times before modern contraception.

Alternatively, the authors of this investigation argue, it could be that historically, traditional methods to avoid pregnancy, for example, breastfeeding ‘infertility’ or fertility awareness, were much more effective than originally credited. This factor then would allow for higher rates of adultery without it being expressed in high ‘extra-pair paternity’ rates.

Biological Drive

All this new data, the authors argue, pose a major challenge to that ‘biological drive’ idea of women ‘shopping around’ for good genes by engaging in extra-pair copulations to obtain genetic benefits for their children.

The authors speculate that there may be several reasons for such a low incidence of ‘extra-pair paternity’ world-wide and across centuries, including perhaps a dread of sexually transmitted infections, risk of spousal violence, divorce or reduced paternal investment by the social partner or his close relatives if the betrayal is discovered.

The fact that women may be a lot more faithful than had previously been imagined may have important and profound psychological impact. We often decide what to do with our lives based on our theories about how everyone else is behaving. If we assume the whole world is sleeping around or that fidelity is rare, it might lower our inhibitions over behaving similarly.

If it’s the case that women were and are more faithful than had been previously assumed, maybe that understanding in itself will influence promiscuity.

All this means that the Archbishop of Canterbury’s experience of his paternity is, in fact, rarer than might be commonly believed, and this fact could in itself have psychological consequences. Beliefs about how common it was for mothers to behave in this manner, could influence his own attitude and coping.

It is possible that the Archbishop’s of Canterbury’s own mother’s statement, as reported by the BBC News site and other media that she recalled sleeping with former colleague Sir Anthony after “a large amount of alcohol on both sides,” reflects some psychology as well.

Fetus image available from Shutterstock

Just How Common is Paternity Surprise?

Dr. Raj Persaud & Dr. Peter Bruggen

Dr. Raj Persaud & Dr. Peter Bruggen are regular contributors to Psych Central Professional. Dr. Rajendra Persaud, also known as Raj Persaud, is a leading consultant psychiatrist, broadcaster and author of popular books about psychiatry. He is well known for raising public awareness of psychiatric and mental health issues in the general media. He has published five popular books and has received numerous awards. The Times recently placed him as one of the Top Twenty Mental Health Gurus in the world.

Dr. Peter Bruggen was part of the UK Royal College of Psychiatrist's Podcast Editor Team, with Dr. Persaud. From 1969 to 1994 he was a consultant psychiatrist at Hill End Adolescent Unit, St Albans. He was also a consultant psychiatrist from 1969-90 at the Tavistock Clinic. His work has featured family therapy at the death bed, working with families in the community rather than admitting adolescents to hospital, and staff relationships. Dr. Bruggen has also written three books, including Surviving Adolescence and Helping Families (both with Charles O'Brien), and Who Cares? True Stories of the NHS Reforms, for which he conducted face-to-face interviews with one-hundred people.


APA Reference
Dr. Peter Bruggen, D. (2019). Just How Common is Paternity Surprise?. Psych Central. Retrieved on August 10, 2020, from


Scientifically Reviewed
Last updated: 25 Sep 2019
Last reviewed: By John M. Grohol, Psy.D. on 25 Sep 2019
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