Wednesday, September 30, 2009

Embryo Swapping

Another example of 'patient mis-identification' with the patient in this case being either the wrong mother or the wrong embryo -- take your pick:

Note that in this case, the mother chose to continue the pregnancy even though the wrong embryo had been implanted. The article goes on to list a similar case where the mother chose to terminate the pregnancy.

Baby Swapping as Patient Mis-Identification

A 2003 story out of Boston highlighted a baby swapping incident as an instance of the broader problem of patient mis-identification:
In this particular case, the mother recognized that the infant given to her to nurse was not her own. What is of interest here is the frequency with which patient mis-identification occurs in hospitals -- with baby-swapping being only a particular example. Despite elaborate procedures to prevent these cases, they occur with depressing regularity.

Friday, June 12, 2009

Preferential Childcare Based on Appearance

New Scientist has an interesting article up this week on variations in the amount of time and resources fathers devote to their children. The study, done in Senegal, found that fathers devoted greater time and resources to children who looked and behaved more like them regardless of gender. Here’s the link:

The authors speculate that in the absence of proof of paternity, fathers look for similarities to themselves when they apportion scarce resources. They link this preferential treatment to the uncertainties of fatherhood.

It would be interesting to follow up this study with one that simultaneously looked at the frequency of non-paternity events in a culture. One would predict that in cultures where the rate of NPEs was high (as determined by DNA testing) the imbalance in preferential treatment based on appearance would be greater.

Monday, May 18, 2009

Twin Half Brothers

In the news this week from Texas, a case of ‘twin’ boys fathered by different men. Their mother was having sex with both men and one ovum was fertilized by sperm from each man. DNA tests were ordered when the twins looked substantially different from each other. Here’s the link:,23599,25500537-2,00.html


Wednesday, May 13, 2009

More Baby Swapping

Another instance of baby swapping surfaced in the press this week. Although the actually swapping occurred in 1953, the exchange of two baby girls in a hospital in Washington state only came to light recently. DNA testing confirmed that the girls had been exchanged while being bathed by nurses. Here’s a link:



Monday, April 20, 2009

Adoption via Kidnapping

An article in the New York Times provides a story about child abduction in China that illustrates by contrast some of the cultural biases in Western/European culture regarding non-paternity events. Some time ago China implemented a one-child policy in order to stem population growth. In a society that traditionally relied on sons to support parents in the old age, this meant that some families with a girl were left without sons. In response, an illegal market has developed for kidnapped toddler boys – stolen from their parents, these boys are sold to families who want a son. This forced adoption results in what is clearly an NPE, but certainly of a different sort than we usually consider.

The article is at:

Friday, April 10, 2009

Cryopreservation World Record

We’ve previously mentioned the potential problem of asynchrony brought about by cryopreservation technology. That is, a man could have his sperm frozen and it could then be used at a much later date to fertilize an ovum. Today’s news brings this example:

“CHARLOTTE, N.C., April 9 /PRNewswire/ -- Fertility specialists of Reproductive Endocrinology Associates of Charlotte (REACH) herald the successful birth of a baby girl March 4 who was conceived through in vitro fertilization (IVF) at their laboratory with sperm frozen for 21 years, which they believe ties the world record for the longest-frozen sperm used to create a baby with IVF.”

The complete article is found at:

Thursday, April 9, 2009

Post-Mortem Sperm Recovery

Lest we think that some of the more unusual methods of assisted reproduction never actually take place, here’s an example of post-mortem sperm recovery with the intent to use it to impregnate a surrogate mother:

In this case there would be no apparent non-paternal event, since the biological father would be known, but a family history research of the future might wonder at the birth of a child so long after their father’s death.

Wednesday, April 8, 2009

A Downside to Artificial Insemination

A recent article in New Scientist illustrates a downside to assisted pregnancy – in this case the sperm used to artificially inseminate a woman passed on so-called fragile X syndrome to the resulting child. The story is at:

One lesson from this is that when the family historian is looking for physical traits that might signal the source of a non-paternity event, they can be misled by recessive or ordinarily unexpressed genes that show up in the child but are not seen in the biological parent.

Monday, April 6, 2009

Modern Baby Swapping

A case of baby swapping in a modern hospital came to light recently. In this case, the substitution was discovered after the baby girl was given to the wrong mother to breastfeed just once, but it illustrates that even with better infant identification routines, mistakes happen. Here’s the story:

Thursday, April 2, 2009

Orphan Trains

As I mentioned earlier, whenever an adoption occurs, the potential for a non-paternity event is created. Memory of the adoption is lost over time and a new genetic component is added to a family’s descendant population. 

Three relatively recent cases of mass adoption under unusual circumstances come to mind when thinking about NPEs. These are the so-called Orphan Trains of the late 19th and early 20th century here in the United States, the forced adoption of the babies of leftist intellectuals murdered during the Argentine junta’s ‘dirty war’ and the adoption of Jewish children by families hiding them from the Nazi extermination camps in the 1930’s and ‘40s. I’d like to take some time to talk about each of these, since they each created a pool of potential NPEs. Let’s start with the Orphan Trains.

The Orphan Trains had a humanitarian goal – to take urban children whose parents were either deceased or unable to care for them and transport them to rural areas where families were willing to take them in. These relocations went on from the early 1850’s to the late 1920s. The technique originated in New York and Boston but was used by a number of eastern cities, some as far west as Ohio. It was driven by multiple motivations: the myth of a pure and bucolic countryside as opposed to the evil cities as places for the children to be raised to adulthood; the desire to unburden agencies of children so others could be cared for; the disposal of children who had run afoul of the authorities; and, of course, a no less real belief that this was a better fate for the children than living in an institution. Estimates of the number of children removed from cities in these programs are upwards of 200,000. 

Children from orphanages and foundling homes as well as some from the equivalent of juvenile detention facilities were put on trains with agents who guided them to a new location. Notice of the availability of children was usually made in the local newspaper. On arrival the children were put on display and claimed by families willing, for a variety of reasons, to take them in. The degree of formality in assigning children to families varied widely. Some agencies insisted that children be ‘indentured’ or apprenticed or formally adopted – this means that a paper trail exists that could be discovered if an NPE is observed through a DNA mismatch. In other cases, no formal adoption was required, although it may have taken place at a later time on the family’s own initiative. Some agencies kept records of which children were sent to which towns and some of those records have been preserved; other agencies did not maintain good records.

The motivations of the families taking in the children varied. Some farmers were just looking for a spare farmhand or a maid. Others did so out of a genuine wish to help. The treatment of the children was as varied as the families that took them in. Some children became an integral part of their new family, others were mistreated and ran away, and still others remained with the family that took them in but never were integrated into the family’s line and left upon reaching their majority.

The agencies that set up the Orphan Trains were sponsored by different groups – some religious and others civic. In general, the religiously based groups might take children of any religious background but put them into families from their own religious orientation. So in tracing back from a discovered NPE, the family historian cannot count on a match between the accepting family and the child’s real (if any) religious background.

Friday, March 27, 2009


A 12-page insert in my morning paper offers articles on fertility and pregnancy mixed in with ads from fertility clinics and drug companies. We’ve talked before about various aspects of assisted pregnancy and its implications for non-paternity events. This morning’s insert brings up another aspect – the ability to preserve eggs, sperm and embryos for long periods of time, usually via cryopreservation or freezing.

Preservation itself, one might think, would have no implication for NPEs. However, it offers the opportunity to shift fertilization or pregnancy in time and to create asynchronies in what is usually a synchronous process.

Let’s consider sperm preservation first. Artificial insemination relies, generally, on the preservation of semen samples from donors that are then used to impregnate women. (There are exceptions – a case a few years ago involved a doctor in New Jersey who would ‘generate’ his own ejaculate on the spot and use it to fertilize his patients. He sired quite a few kids before the practice was discovered.) By preserving the semen, a woman may become pregnant with a man’s child after his death. Obviously, this isn’t limited to the artificial insemination case. Sperm is now preserved by in vitro clinics, by men who are about to undergo radiation treatments and by men who are about to go overseas to war in anticipation of injury or incapacity.

There are also new techniques for harvesting viable sperm from the recently deceased, or so the lead article in the insert informs me. The point here is that the recovery and preservation of semen offers the possibility of men siring children long after their own death, and perhaps with women they did not know. Newer technologies that preserve ova offer this same possibility in the case of women.

So how long do frozen sperm and ova remain viable? A Mayo clinic study found no difference in fertility between fresh or frozen sperm, but the freeze interval was not specified. There has been at least one case where sperm frozen for 19 years was used successfully to fertilize an ovum and resulted in a full-term pregnancy. Studies done with other species indicate that sperm frozen in liquid nitrogen (about -322° F) remain viable for remarkably long times – trends in viability decreases indicate that frozen sperm could still be viable after 10,000 years. Ova freezing is a newer technique and viability is not as high as for sperm, although that could improve as studies continue. At least so far, freezing embryos has been more successful than freezing ova.

We have the possibility with these new techniques for children to be born long after their biological parents have died. The imagination reels at the variety of NPEs made possible through intent or accident. What family historian is prepared to tease out actual inheritance when generations could pass between parents and the birth of their children?

Sunday, March 22, 2009

Dark Italian

I ran across an interesting account of a non-paternity event from the point of view of the child. David Paladino was the son of an Italian-American girl who was having simultaneous affairs with an Italian-American boy and an African-American boy. When she got pregnant, she married the Italian-American and Paladino grew up as a ‘dark Italian’. As you might guess, the African-American was his actual biological father. Here’s a link to an interview with him:

 There was also a program on This American Life devoted to his story. You can find it at:

An Example of Baby Swapping

I subscribe to the podcast of This American Life. A recent podcast called “Switched at Birth” offers an interesting example of what we talked about earlier as ‘Baby Swapping’. In this case, two baby girls were born in the same delivery room within minutes of each other and accidentally switched on their way to the nursery. One mother suspected the switch but didn’t tell the daughters until they were 43 years old. The podcast is at:

Monday, March 16, 2009

Chimerical Complications

We talked about chimera earlier – individuals who are the result of the merger of two zygotes at a very early stage of development. Different parts of the body develop from the stem cells related to the two different zygotes so the individual ends up being their own sibling, with some organs and fluids from one zygote and others from the other.

It turns out that the chimera phenomenon is a little more complicated than this ‘simple’ picture. Let’s start out by talking about some good news for pregnant women – researchers have been able to verify that there is ‘leakage’ from their fetus into the mother’s blood stream. That is, cells from the fetus make their way across the placenta or through the wall of the uterus and are found in the mother’s blood. Why good news? This means that you can take a blood sample from the mother, identify cells from the fetus, culture them and find out things about the fetus – its gender, whether it carries specific genetic disorders that can be treated in utero and so on. This means that for many genetic tests the day will come when we no longer have to do invasive procedures such as amniocentesis or chorionic villi sampling.

Now let’s add a couple of other bits of information. First, in some women fetal cells are not eliminated from the mother’s bloodstream after birth but persist. Second, transfer of cells also occurs from mother to fetus. Suddenly we have the prospect of a lot of genetic material floating around that may or may not be incorporated into a developing fetus. Genetic material from prior pregnancies may persist and may become part of a new fetus, creating a chimera. Consider, for a moment, the implications for the children of surrogate mothers who have their own children or have carried surrogate pregnancies for multiple couples.

Before we get too disturbed by all this, let’s concede that standard chimera are relatively rare and the type of genetic transfer just discussed is probably rarer still. On the other hand, like babies with webbed feet and tails, it does occur and could result in apparent or actual NPEs.


Sunday, March 15, 2009


Enough biology for a while – let’s talk about meddling. I’m referring to non-paternity events that are set up by the meddling of the authorities, however one defines them.

I have a particular case from my own family history in mind. One of my 6th great grandfathers, Michael Gabel was born near Erbach, Wurtemburg in what is now Germany in the early 1730s. He emigrated with his parents, arriving in Philadelphia in 1749. The family settled in Hanover Township of Montgomery County, PA, just north of Philadelphia. After the death of Michael’s mother, his father remarried a widow who had children of her own. Michael married his step-sister, Anna Breisch in early 1753.

After some consideration, however, the Lutheran church elders decided that the marriage of step children was not permissible and annulled the marriage. Anna, however, was already pregnant with their son. Next, he married Margaret Elizabeth Ruth (sometime in the fall of 1753). But this marriage was set aside because it occurred before the birth of his son by Anna. Third, he married Anna Maria Baltzhauser (in June, 1754), but this marriage was annulled because the church fathers decided he was still really married to Margaret Elizabeth Ruth. He had quite an exciting year or so.

Michael Gabel ended up married to my 6th great grandmother Margaret Elizabeth Ruth and they had a lot of kids. What about Anna Breisch and her son by Michael? She ended up married in 1754 to a widower named Johann Jacob Danner, taking the boy, who had been baptized Hans Martin Gabel, with her. After her marriage, she, her husband and her son disappear. Did Hans Martin take on his step-father’s surname? If so, we have another NPE on our hands, this time owing to the meddling of church elders.

Friday, March 13, 2009


A few years back, a woman in Massachusetts was suffering from kidney failure and she and her sons underwent tests to see if either of them would match as a donor. Her doctors informed her that not only did they not match, but neither of them could be her child. A double case of baby swapping? The actual situation was even less probable.

After extensive tests of various body tissues and fluids, it became apparent that the woman was a chimera – that is, she had two separate genetic identities that were the equivalent of sisters. Some organs, including her ovaries related to one of the genetic identities, while others, like her blood and kidneys, were related to the other. So her sons inherited a different genetic makeup than the one that determined her kidney compatibility needs.

Chimera are created when two fertilized eggs merge at a very early stage of development and different parts of the body develop from the stem cells from the two genetic sources. While rarely detected, chimera may occur more often than we think. Scientists have identified over 30 cases so far, including one of a man who was the product of the merger of one male and one female zygote. When operating to free what they thought was an undescended testicle, doctors discovered a uterus and fallopian tubes.

Let’s consider the implications of chimera for non-paternity events. If it is possible to have chimerical functioning sets of both male and female organs, it is also possible to end up with chimerical sets of male testes. The latter situation could arise when zygotes fertilized by two different men merge and one genetic makeup is expressed in one testicle and the other in the second. If this man then has children, his sons could be descended from either ‘grandfather’.

Another scenario might produce an apparent NPE when none exists. Consider a woman whose mother has blue eyes (two blue-eyed genes) and whose father has brown eyes, but who has one blue and one brown-eyed gene. Some of their children will have blue eyes and some brown. However, a chimerical child could develop blue eyes but have ovaries that produce ova with a brown-eyed gene. If she then marries a blue-eyed man, their children could have brown eyes. Just how do you explain that event to a skeptical husband?

Thursday, March 12, 2009

The Persistence of Sperm

Biology has a way of confounding our social expectations. And in some cases this leads to a curious variant of non-paternity event. Sensitive readers might want to skip on to the next post.

The particular incident I have in mind occurred among US military personnel and their families stationed in Germany. The Caucasian wife of a Caucasian army non-com gave birth to a child with obvious African-American heritage. Aha, we say, we know what went on here – an obvious case of marital infidelity, one of the classic sources of NPE. Well, yes and no. In this case, the mother had not had sex with anyone but her husband and there was no accident in an in vitro lab either.

Her husband, however, had been having an affair with the wife of an African-American soldier. She had had sex with her husband shortly before then having sex with her lover – who then went home and had sex with his wife. While we can marvel at the degree of lust and capacity of these individuals, the real standout here was sperm. The child in question was product of sperm from the second husband that had attached itself to the adulterer’s penis and then escaped into the first wife’s uterus.

The different ethnic origins of the people involved here made the outcome apparent, but the lesson is that pregnancies result from the joining of a sperm and an ovum – however that conjunction occurs. We can’t assume an NPE results from a wife’s infidelity – it could be the husband who brought home some persistent sperm. However it arrives, sperm may still be viable and result in a pregnancy. I recall a story that made the rounds when I was in college about a co-ed who claimed she had gotten pregnant after putting on a pair of her roommate's panties by mistake – well, perhaps I shouldn’t have been so skeptical!

Wednesday, March 11, 2009

Name Changes

Another source of apparent non-paternity events is a change in surname. There are many possible reasons for a man to change his surname. Some examples are to simplify spelling, conversion to a common spelling in a new country and adoption of the wife’s maiden name.

The first two cases could be the results of immigration. As a country of immigrants, the United States is fertile ground for this kind of name change. Contrary to common belief, officials at Ellis Island rarely changed names, but immigrants often did. This can result in DNA mismatches to different presumed family lines if an immigrant’s sons changed their names differently. In my own family history, for example, I have a Johann Weiss who emigrated from Alsace sometime before 1850. He appears in some records as ‘White’ (the English translation of the name), others as ‘Weiss’ and still others as ‘Wise’ (adoption of a common English name that is similar). It is probably for the best that he didn’t adopt ‘Vise’ or even worse ‘Vice’, following the actual German pronunciation. In any case, if his sons had each adopted a different method of changing the name, a researcher attempting to match DNA with their variant could be disappointed.

Another source of name change was when a husband adopted their wife’s maiden name. This sometimes occurred when there was no male heir in the wife’s family and her father wanted someone to carry on the family name. An estate or fortune to go along with the name might be a sufficient incentive. In Ireland, a similar name change could occur when a spinster held land or the lease to land and brought in a man to manage or farm it. These men, whether related or not, would sometimes assume the woman’s surname.

Fraud also comes to mind, and shouldn’t be ruled out if there is no DNA match for a line you are tracing and others sharing the surname. Our ancestors got into a variety of scrapes for which a hasty departure and a change in identity served as the easiest remedy. This sometimes led to the creation of two separate families with children with different surnames, but a common paternal heritage.

Tuesday, March 10, 2009

Baby Swapping

Some Non-Paternity Events are the result of what might be called baby swapping. That is, one baby is substituted for another.

For the last century or so many children have been born in hospitals rather than at home. Babies are kept in nurseries with many others and delivered to their mothers periodically to be fed. Despite precautions, sometimes babies get mixed up and the switch is not recognized. In one notorious case, two baby girls were switched and the substitution was not recognized for more than a decade. The substitution came to light when one of the girls died and it became apparent that the cause of death was an inherited condition. The family that thought she was their daughter could not have transmitted the disorder. Eventually, the other girl was identified – the mother in the family that she had been living with had died of the same disorder as the other daughter. DNA testing confirmed that the girls had been switched. The widower, the surviving girl and the biological parents were then faced with the dilemma of which family should be raising the girl. The girl chose to stay with the man who had raised her, at least initially.

The point of this tragic story is just that babies do get mixed up accidentally. It is also the case that sometimes the switch is done deliberately. For example, if a baby was a stillbirth or born sickly and died soon after birth, an orphaned or illegitimate baby was sometimes substituted. This might be done to insure an heir to a family or to simultaneously comfort the bereaved mother and solve the problem of the orphaned or bastard child. In either case, the substitution can result in DNA mismatches down the road. Hospital births and mandatory birth registration have reduced this deliberate substitution, but not eliminated it.

Monday, March 9, 2009


Another source of apparent non-paternity events is adoption. This is not usually thought of in the same context as marital infidelity, but for the family historian, the results are similar – that is, a mismatch between the social parents and the biological inheritance of the child.

Modern adoption is usually thought of as bringing a child unrelated to either parent into a family. There are notorious cases (such as the Orphan Trains or the forced adoptions of the babies of purged leftist parents in Argentina) where this was done on a mass scale. In many cases, adoptees were not told they were adopted and were given no information about their biological parents. If an adoption occurred several generations in the past, a mismatching DNA test could lead to questions about the nature of the NPE that could not be answered by any living relative.

Generally, however, this was less common in the past than a couple raising related children, particularly nieces, nephews or grandchildren, after the deaths of their parents. I have a case in my own family history where the death of a young girl’s mother led to an offer of adoption by an infertile aunt. Higher death rates among younger adults left many more children orphaned in the past than in modern times. These adoptions were not always formal, even though the children sometimes assumed their adoptive parents’ surname. In cases where an adopted son was the offspring of the husband’s brother, no NPE would be evident even from a yDNA test, although mitochodrial DNA would reveal a different maternal ancestry.

Where an NPE is observed, the family researcher should look at possible DNA matches other relations (such as the wife’s or son-in-law’s family) or with neighbors. If you find death records for a sister and her husband followed by the appearance of previously unknown children in a family, it could indicate adoption.

Sunday, March 8, 2009


When one thinks of infidelity in the context of a non-paternal event, the obvious scenario is a wife having an affair with a man not her husband. However, there are several variations on infidelity that become important to the family historian.

First, there is the question of the identity of the man the wife is having a sexual relation with. The common assumption is that it is someone unrelated to the wife or her husband. This, however, is not always the case. There was a news story several years ago about a woman who drowned her two children by driving her car into a lake with them strapped in their car seats. Although the focus of the news media was on the act itself, it came out later that the children were the products of an incestuous relationship with her father, a prominent local businessman. Other incestuous relationships, with a brother or paternal uncle would produce a biological link of the children with their mother’s paternal ancestry, while an affair with a maternal uncle or cousin would link to the wife’s mother’s paternal ancestry. On the other hand, an affair with the husband’s brother/father/paternal uncle would not show up as a DNA contradiction but such an NPE might be reflected in divorce, abandonment or disinheritance by the husband if discovered.

Once an NPE is revealed, the family historian should begin thinking about who the biological father might be. If DNA testing of the lines of neighbors’, employers’ or the wife’s line is available, a comparison of the yDNA might reveal their identity. Of course, when there are multiple men of an appropriate age present, a yDNA match can only limit possible fatherhood to that set rather than a specific individual. The case of Thomas Jefferson and his relation with his slave Sally Hemmings, for example, gives us good reason to believe he fathered her children, but the DNA match does not exclude his male relations.

Of course, infidelity is not limited to wives. Husbands also had affairs that resulted in offspring and sometimes these children were given their mother’s surname, and sometimes their biological father’s. These ‘natural’ children were sometimes acknowledge and supported and in some cultures were given surnames that reflected their heritage. The prefix ‘Fitz’ (as in Fitzgerald), for example, indicates a son born out of wedlock. In some Scandinavian countries, the child would get the usual designation, e.g. Hakkons-son or Hakkons-totter, and then might also get additional surname that reflected where they were born.In cases where the child’s surname did not match their biological father’s, there will be a DNA mismatch between others of that surname and their line.

One additional point that should be mentioned is that the identity of the father in cases of marital infidelity is not always clear. Just because a man acknowledges that a child could be his does not mean that he is actually the father – only the introduction of blood type and DNA testing has allowed us to establish this with reasonable certainty.

There are some other interesting variants of infidelity that I will discuss later, since they involve unusual circumstances.

Saturday, March 7, 2009

Assisted Pregnancies

Before we move on to talk about ‘traditional’ non-paternity events I’d like to mention some of the ways that modern science appears to be complicating the family historian’s lot.

Let’s start with artificial insemination, one of the older methods of assisting women whose husbands are infertile to get pregnant. Sperm donors deposit semen that is stored until a recipient chooses the donor from a list and it is then injected in the woman’s uterus at her peak period of fertility. Until recently, sperm donors remained anonymous and many couples who used artificial insemination did not inform their children that their social father was not their biological father. This sets up the classic NPE situation.

In recent years, some states have set up voluntary sperm donor identification registries. Donors who are willing to be identified register and children they sired can find out who their biological father is. Some men whose description and profile proved popular have discovered that they have dozens of children and seem rather bemused at the concept.

In vitro fertilization is a technique usually employed to allow couples who for some reason cannot conceive naturally to generate a fertilized egg that is then implanted. Sometimes multiple embryos are implanted to insure that at least one will ‘take’. Normally, the husband sperm and the wife’s ova are used for in vitro fertilization, but this is not necessarily the case -- a sperm or egg donor could be used. The donor could be related (e.g., the husband’s brother or the wife’s sister) or unrelated. If the resulting child is not informed of the nature of their conception, the usual NPE situation is set up.

A case that illustrates the perils of in vitro fertilization occurred in the Netherlands. A Dutch couple used their own sperm and ova to produce embryos that were implanted and resulted in the birth of twin boys. One of the boys, however, was clearly not the husband’s – he was darker skinned and looked part Indian. In fact, he was. The fertilization lab had used the same pipette to transfer sperm to fertilize ova for two successive clients and sperm from the Indian man from the first couple had stayed in the pipette and fertilized one of the Dutch woman’s ova.

Another recent practice, that of surrogate motherhood, can also result in an NPE. Surrogates have the option in most states to renege on their contract and to keep the child they have carried. In some cases, this may be regardless of whether it was their ovum or that of the woman from the employing couple.

Ova donors set up a situation parallel to that of sperm donors. And embryo donation, encouraged in some states to preserve unused embryos from in vitro procedures, presents us with another case where a woman can get pregnant and carry to term a child that is completely unrelated to her or her husband.

Friday, March 6, 2009

Rate of Non-Paternal Events

When you attempt to eat a grapefruit, there is a chance that you will press the wrong way when prying out a section and squirt yourself in the eye. Since this is startling and painful you remember it and, if asked how often it happens, you tend to exaggerate its frequency. Similarly, when you discover a non-paternal event in your family, it sticks in your mind. I’ve come across four documented instances in my own family history and it seems like a lot until I realize that I have around 4200 individuals in my database.

What is the real rate of NPEs? Well, it depends. Estimates range from one in a hundred to one in five. Studies that have used DNA or blood types indicate that the rate of NPEs varies across ethnic, religious and economic groups. When cohesive religious groups (such as Mormons or Orthodox Jews) are studied the rate of NPEs is between 1% and 1.5%. Lower socioeconomic groups have higher rates of NPEs than wealthier groups. A study of working class families in the British Midlands that used blood types showed that a fifth of the children could be NPEs, although the criteria used to establish that were somewhat loose.

An interesting angle on this question has been taken by researches looking at sibling pairs used in medical research on genetic markers for various disorders. Since full siblings share more of their genetic makeup than half siblings, it is important to know the rate of NPEs. In order to establish a base rate for NPEs, the researchers studied genetic variation among men with the same surnames. In Britain, common people adopted surnames sometime after the Norman Conquest (1066). Some of the surnames were taken from a man’s occupation (e.g. Smith), others from their father’s name (e.g., Johnson), and so on. It is not too surprising, then, that occupational surname lines had a lot more founding fathers than surname lines based on a unique location or unusual physical characteristic. When the researchers looked at genetic variation among men with different surnames, they found that the variation was high among common surnames and low among rare surnames. This is because rare surnames are likely to have had just one founding father. For uncommon surnames, they were able to estimate the rate of NPEs at between 1 and 1.5%. Now it is unlikely that people with uncommon surnames have a lower rate of NPEs than those with common surnames, so we can take this as an overall estimate of NPEs in the general population.

Family history researchers have different reactions to NPEs – some horrified, some titillated and some gratified that their ancestors were human after all. The rate of NPEs revealed by these studies suggests that it is an infrequent but not unheard of event.

Thursday, March 5, 2009

What's an NPE?

A Non-Paternal Event (NPE) is an instance where a child’s biological and social fathers are different. The old saying, "Mama’s baby, Daddy’s, maybe", sums up one view of this situation. This blog explores the different varieties of NPEs and their complexities -- including a child’s biological and social mother being different (with some recent novel variations).

If you are researching your family history, you may encounter situations that suggest that a child is not the son or daughter of the couple raising them as their own. One of my great-grandmother’s, for example, had three more children after her husband died but indicated in public records that he was the father of all three. Now the one born nine months after his death we can probably accept, but the next two are the results of NPEs.

Because of European surname inheritance customs that developed in the last 500 years or so an NPE is often seen as a mismatch between the child’s biological inheritance and their social father’s surname. There is a persistent concern among some genealogists with what’s been called blood inheritance. That is, the rejection or disregard of social inheritance and an insistence on actual biological inheritance as the only ‘true’ genealogical link.

Although the family historian’s traditional methodology was limited to tracing the social family, there were some records, such as guardianships, adoptions and orders of support for children born out of wedlock that documented NPEs in the past. We now have the additional complication of DNA testing, which can show that various members or entire branches of a socially coherent family tree are, biologically at least, not related and thus the product of an NPE at some time in the past.

As I explore the NPE concept, I hope you will join in the discussion and provide examples from your own experience or family history that shed additional light on the subject.