This is the fourth and final segment in a series on incest; you can go back and read the previous segments on incest in ancient Egypt, incest in the Hapsburg family, and incest in nature.

As surprising as it may seem, consanguineous marriages are nowadays respected and practised among more than one billion of the world’s population, in particular in the Muslim countries of North Africa, Central and West Asia, and in most parts of South Asia (Jalal Abbasi-Shavazi 2008) with consanguinity rates reaching 20–50% (Hamamy 2016). It has been shown (Bittles 1994, 2001) that sociocultural factors, such as the maintenance of family structure and property, ease of marital arrangements, better relationships with in-laws, and financial advantages relating to dowry, seem to be strong contributory factors in the preference for consanguineous unions.

In countries with civil unrest, consanguineous marriages are preferred because close-kin marriage is regarded as safeguarding for personal and family. It has also been suggested that marriage dissolution and divorce is lower among cousin couples. Studies have indicated that women in first-cousin marriages are protected against intimate partner violence. In another study focussing on cases of consanguinity in Iran (Jalal Abbasi-Shavazi 2008), the authors also demonstrate that in this country the ethnicity, province and area of residence have remained by far the most important determinants of the practice of marriage to biological relatives. In contrast, the modernization variable, education, had no significant effect upon behaviour, the effect being only for those with tertiary education.

Figure 1: Global prevalence of consanguinity (Bittles 2009)

In other countries, the genetic risk associated to consanguineous relations is taken very seriously and all is done to avoid it. This is the case with Iceland. With a population of only 320.00 inhabitants, the risk of incest is really high. De facto, in Iceland everyone shares at least one family relationship. It is said that one of the most asked questions during a first date is: “Hverra manna ert þú?” Which means “ Who are you, who is your family?” To avoid any chance to end up dating your cousin, 3 engineers have recently created a smartphone app called ÍslendigaApp in which people can check the family genealogy and any family relationship with their intended in a few seconds. It even has a “bump” option which gives the info on family relationships when the partners’ phones are clashed and can even send an “incest alert” when the two partners are close family members.

At the origin of this app, there is a genealogy website called Íslendingabók (i.e. Book of Icelanders). Launched in 2010, the database lists the family relationships between Icelanders going back 1200 years. To check the information related to your family, any inhabitant of the Island only needs to provide his/her name and national identity number. Quickly, the website starts to be much more than just a catalogue of genealogy trees and people started to use it to check any possible family connections to their partner.

Here the series on Incest ends. Through the different articles of this series, I have tried to elucidate the incest taboo, find its sources, and understand its origins through different historical cases — Tutankhamun or the Habsburg family — but also through scientific cases.  All these examples have shown us that this taboo seems deeply anchored in nature and culture but that neither nature nor some cultures totally prohibited it. So where to find its source? The questioning hits some dead-end; the answers provided are always partial. Psychology has tried to stick its nose into it while some scientists are waiting for the discovery of a possible “incest” gene. While we wait for answers, I would like to ask you: “Why do you find incest disgusting?” I hope these articles gave you some food for thoughts and starting points for further questioning.

“There is nothing either good or bad, but thinking makes it so” (Hamlet by W. Shakespeare).

References

Bittles A. H. (1994). ‘The role and significance of consanguinity as a demographic variable.’ Population and Development Review 20(3):561-583.

Bittles A. H. (2001). “A Background summary of consanguineous marriage.” Center for Human Genetics, Edith Cowan University, Perth.

Bittles, A. H. and M. L. Black. “Consanguinity, Human Evolution, and Complex Diseases.” Proceedings of the National Academy of Sciences 107.Suppl 1 (2010): 1779-86. Web.

Hamamy, Hanan, and Alwan, Sura. “Chapter 18 – The Sociodemographic and Economic Correlates of Consanguineous Marriages in Highly Consanguineous Populations.” Genomics and Society, 2016, pp. 335–361.

Jalal Abbasi-Shavazi, Mohammad, et al. (2008). “modernization or cultural maintenance: the practice of consanguineous marriage in Iran.” Journal of Biosocial Science, 40(6):911–933.

Welcome back to this series of articles on Consanguinity in History. In my previous article, you have heard about incest in Ancient Egypt and the case of Akhenaton and his son Tutankhamun. Let’s continue our investigations around consanguinity and look at another famous case: Charles II from the Spanish branch of the Habsburg family. We often hear that consanguinity is dangerous for the future child, but how dangerous is it exactly and why? The family story of this king followed might give you some food for thoughts.

Between the 15^th and the 18^th century, the Habsburg family ruled the Holy Roman Empire and, as such, was the most influential and powerful royal family in Europe. In the 16th century, the family separated into the senior Habsburg Spain and the junior Habsburg Monarchy branches, who settled their mutual claims in the Oñate treaty.

The kings of the Spanish Habsburg dynasty, and of the Habsburg house in general, are known to frequently marry close relatives in such a way that uncle-niece, first cousins and other consanguineous unions were prevalent in that dynasty.

Figure 1: Family tree of the Spanish branch of the Habsburg family (kings are in capital letters) showing the inbreeding among Charles II ancestors. (Source: Alvarez et al.)

This branch disappeared in 1700 with Charles II, which many say was because of his family’s rampant inbreeding (see Figure 1). Charles II was indeed famous for being one of the ugliest kings. His nickname was El Hechizado or the Bewitched. He probably suffered from two genetic disorders. First, there was combined pituitary hormone deficiency, a disorder that made him short, impotent, infertile, and weak with a host of digestive problems. The other disorder was distal renal tubular acidosis, a condition marked by blood in the urine, weak muscles and having an abnormally large head compared to the rest of the body.

Figure 2: Portrait of Charles II of Spain (1661-1700) as well as two of his uncles and ancestors (Charles V (1500-1558) and Emperor Leopold I (1640-1705) (credits: Wikimedia Commons).

In order to understand the origin of these disorders, scientists have often used genetic analysis (such as in the case of Tutankhamun and Akhenaten) but not always. Gonzalo Alvarez et al. at the University of Santiago de Compostela recently came up with another innovative approach that enabled them to study 3000 family members of the Spanish branch of the Habsburg family over 16 generations. Using computational calculation of the coefficient of inbreeding (F) of each family member, the team was able to unravel the family history and its consequences on Charles II genetic disorders. The coefficient of Inbreeding (F) corresponds to the probability of finding, at a given position on a chromosome, two genes which are identical by descent. For two first cousins, for example, this probability will be equal to 1/16. For these reasons, consanguinity and inbreeding may significantly impact the occurrence and recurrence of recessive conditions and congenital anomalies (Holt 2013). This may lead to birth defects or children with genetic conditions.

These researchers showed that the inbreeding coefficient for Charles II (0.257), Phillip III (0.218) and prince Charles^[1] (i.e. Don Carlos) (0.211) were the highest measured for all the kings of the Spanish Habsburg. This is not surprising as they were all born from either uncle-niece (Charles II and Philip III) or double first cousin (Prince Charles) marriages. However, what was surprising is that the coefficient calculated for each of them were almost twice the expected value for those types of consanguineous marriages (F = 0.125 in either uncle-niece or first cousins relationships) and very close to the expected value in an incestuous union as parent-child or brother-sister (F = 0.250 in both cases). These results were particularly stricking as they showed that “The inbreeding of the Spanish Habsburg kings was not only the consequence of a few generations of unions between close relatives as it is sometimes claimed” but that “ancestral consanguinity from multiple remote ancestors makes a substantial contribution to the inbreeding coefficient of the Spanish Habsburg kings and the contribution of this remote consanguinity is very similar in magnitude to that due to close consanguinity”.

By looking at death records for the family, Alvarez also found that children were much less likely to survive till their tenth birthday if they were born to kings with high F-values. The growing degree of inbreeding in the family meant that fewer and fewer children made it to adulthood, leaving the entire line resting on an infertile, handicapped and short-lived king. Paradoxically, it is thus the same desire that pushed the royal family to preserve the purity of their blood and to keep the “power” within their family that led them to lose it.

But inbreeding did not impact directly the royal lineage. It is, instead, the repeated inbreeding practice that gradually weakens the descendants’ mental and physical health. Incest simply increases the risk that the two parents share the same congenital condition which could then be transmitted to the child. But, what prevents two parents from different families to also share this anomaly? Nothing. Also, it has been shown that having a child with your first cousin raised the risk of a significant birth defect from about 3-to-4 percent to about 4-to-7 percent (Bennett et al., 2002). The authors concluded that this difference wasn’t enough to justify genetic testing of cousin couples and that most of the stigma associated with cousin unions in occidental cultures has little biological basis.

The incest taboo is resolutely very strong…

In the next episode: incest in the animal kingdom. An article in which you will hear about mongoose, termite which reproduce by producing clones of themselves, fish, salamanders and many more. Incest in nature is surprisingly more common than what you would think…

References:

Alvarez G., Ceballos F.C., Quinteiro C. (2009) The role of inbreeding in the extinction of a European royal dynasty. PLoS ONE 4: e5147.

Bennett, R., Motulsky, L., Bittles, A., Hudgins, G., Uhrich, A., Doyle, L., . . . Olson, R. (2002). Genetic Counseling and Screening of Consanguineous Couples and Their Offspring: Recommendations of the National Society of Genetic Counselors. Journal of Genetic Counseling, 11(2), 97-119.

Holt, R. L., and Trepanier, A. (2013). Genetic Counseling and Clinical Risk Assessment-Chapter 21. Emery and Rimoin’s Principles and Practice of Medical Genetics, pp. 1–40.

^[1] Prince Charles was also strongly affected by his ancestors’ consanguineous unions. His behaviour suggests that he suffered from some serious mental problems. Rumour in the Spanish court had it that he enjoyed roasting animals alive and in one occasion blinded all horses in the royal stables. At age eleven he ordered the whipping of a serving girl for no known reason. Stories about Charles’ misconducts are numerous.

My curiosity was piqued during one of my turns at the Petrie Museum. Facing all these artefacts, traces of dynasties of pharaohs, I was suddenly reminded of the stories of incest and marriages between brother and sister which were common in ancient Egypt among the ruling class. More recently, the topic was brought up again by another visitor. I was then told about Akhenaton’s androgynous appearance that could have been a result of the incestuous practices of the time. This practice seems to be a common thing and these stories made me immediately think of the Greek and Roman gods and their intricate family-love relationships. With this thought came then one question: why would pharaohs marry their sister, mother and other relatives? To act as living gods? To preserve the purity of their blood?

Fig. 1: Limestone statuette of Akhenaten, Nefertiti and Princess (Tell el Amarna). [Petrie museum, UC004]

Many others questions followed: If incest was accepted in ancient Egypt among the ruling class, was it tolerated by the whole population? What makes it unacceptable in Western countries today? Health? Morality? Are marriages among siblings and/or first cousins still allowed nowadays in some countries? And what are actually the risks of incestuous relations?

From ancient Egypt to the Habsburg family in Europe, throughout history cases of consanguinity — mainly among members of the ruling classes — are numerous. It is surprising that the practice continued for as long as it has when religious and civil laws started to forbid it and when the risks associated to this practice started to be known; from the 5th century BCE, Roman civil law already forbade couples from marrying if they were within four degrees of consanguinity (Bouchard 2010). From the half of the 9^th century CE, the church even raised this limit to the seventh degree of consanguinity and the method of calculating degrees was also changed. More recently, modern philosophers and thinkers argued that the prohibition against incest was a universal phenomenon, the so-called incest taboo . But this theory seems contestable in view of the Egyptian case.

So why is it that incest was accepted and practised in ancient Egypt and more recently among members of the royal family such as the Habsburg (16^th-18^th century)? And how did science shed the lights on family relationships, incestuous practices and the diseases resulting from them?

Let’s first take the case of the 18^th dynasty, the first dynasty of the New Kingdom of Ancient Egypt.

Incest in Ancient Egypt: the case of the 18th Dynasty

There is an abundance of evidence showing that marriages or sexual relations between members of the “nuclear family“ (i.e. parents, children) were common among royalty or special classes of priests since they were the representatives of divine on Earth. They were often privileged to do what was forbidden to members of the ordinary family. During the Ptolemaic period (305 to 30 BCE) the practice was even used by King Ptolemy II as “a major theme of propaganda, stressing the nature of the couple, which could not be bound by ordinary rules of humanity” (Chauveau, M.).

Fig. 2: Alabaster sunken relief depicting Akhenaten, Nefertiti, and daughter Meritaten. Early Aten cartouches on king’s arm and chest. From Amarna, Egypt. 18th Dynasty. [Petrie Museum, UC401]

But let’s go back to the 18^th dynasty (1549/1550 BCE to 1292 BCE). In 2010, a team of Egyptian and German researchers analysed 11 mummies dated from the 18^th dynasty which were closely related to Tutankhamun (Hawass, Zahi, et al.). The mummies were scanned and DNA extraction on bone tissues was carried out. The information they could get from these analyses enabled them to identify the mummies, determine the exact relationships between members of the royal family, and to speculate on possible illnesses and causes of death.

The results of the DNA analyses show that Tutankhamun was, beyond doubt, the child born from a first-degree brother-sister relationship between Akhenaten and Akhenaten’s sister (see Fig. 3). Moreover, the authors provided an answer to the androgynous appearance of Akhenaten. They actually showed that the feminized appearance exhibited by the art of the pharaoh Akhenaten (also seen to a lesser degree in the statues and reliefs of Tutankhamun) was not related to some form of gynecomastia or Marfan syndrome as suggested in the past. Neither Akhenaten nor Tutankhamun were likely to have displayed a significantly bizarre or feminine physique. The particular artistic representation of persons in the Amarna period is more probably related to the religious reforms of Akhenaten.

However, the incestuous relationship between Akhenaten and his sister may have had other consequences. Pharaoh Tutankhamun suffered from congenital equinovarus deformity (also called ‘clubfoot’). The tomography scans of Tutankhamun’s mummy also revealed that the Pharaoh had a bone necrosis for quite a long time, which might have caused a walking disability. This was supported by the objects found next to his mummy. Did you know that 130 sticks and staves were found in its tomb?

Fig. 3: Genealogical tree showing the relationship between the tested mummies dating from the 18th dynasty (Source: Hawass, Zahi, et al.).

Fig. 4: Scans of Tutankhamun feet (Hawass, Zahi, et al.)

Incest and common people

This article on consanguinity and incestuous marriages could easily finish here. We learned that incest was practised in ancient Egypt for strategic reasons, in order to preserve the symbolism which associates the pharaoh to a living god. We also saw how science could help us in unravelling the true stories lying behind myths, speculations and rumours.

This could be almost perfect but the incest taboo is more complex than this. As observed by Paul John Frandsen, “in a society (such as ancient Egypt) where nuclear family incest is practised there is no discrepancy between what is licit among royalty and in the populace”. Indeed, contrary to what is often admitted incest was not only reserved to the ruling class. In Persia and ancient Egypt, incestuous relationships between members of non-royal nuclear families also existed (Frandsen P. J.). This shows that incestuous relationship in the nuclear family could be more than just propaganda and that other reasons might have motivated this practice. It has been argued that this was done for economic reasons as endogamy could have been a means to keep the estate undivided and/or avoiding paying bride price. However, these arguments have been dismissed. Up till now, there is thus no reasonable explanation for the lack of incest taboo in ancient Egypt and Persia.

Keep an eye out for my next post, where I’ll talk about incest in the Habsburg royal family and King Charles II of Spain (also called “the Bewitched”)!

References (and read more!)

Bouchard, Constance Brittain. Those of My Blood : Creating Noble Families in Medieval Francia. University of Pennsylvania Press, 2001.

Chauveau, Michel.MmNm. Egypt in the Age of Cleopatra : History and Society under the Ptolemies. Cornell University Press, 2000.

Hawass, Zahi, et al. “Ancestry and Pathology in King Tutankhamun’s Family.” JAMA, vol. 303, no. 7, 2010, pp. 638–647.

Frandsen, Paul John,MmNm. Incestuous and Close-Kin Marriage in Ancient Egypt and Persia : an Examination of the Evidence. Museum Tusculanum Press, 2009.