15 Genetic Mutations That Can Arise from Incest

Incest is a taboo in pretty much every culture around the world, but it wasn't always so. Nobles and royals used to try to keep royal blood pure by marrying people they were related to; Egyptians rulers, in particular, would often marry their siblings or even their own children. This gave us a glimpse of the serious genetic mutations that can arise from incest. But how exactly do you get genetic problems from incest?

1. The Habsburg Jaw



This genetic condition, also called prognathism, is another connected to noble families. The House of Habsburg came to power during the mid-1400s and remained there until the mid-1700s, but during that time, there was quite a bit of interbreeding. Rather than marrying outside the family, the Habsburgs arranged close marriages to protect their interests. Unfortunately, their genetics paid the price. Their children started to show long, jutting lower jaws, with severe under-bites.

The worst case of this was found in Charles II of Spain, who had an under bite so severe that he could not speak properly, could not chew, and had problems with drooling. (In addition, he was infertile and had cognitive disabilities: he learned to talk when he was 4, and to walk when he was 8.)

Even modern ancestors of this family show slight variations of this genetic problem, showing just how long-lasting the results of genetic mutations from incest can be.

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2. Elongated Skulls



If you look at many ancient Egyptian busts, you may notice that their heads look a little funny - in particular, they are often elongated in the back. This wasn't just a stylistic choice on the part of the artist; many Egyptian royalty actually had skulls shaped like that. A large part of this is that Egyptian royal customs depended heavily upon incest. Brothers married sisters, mothers married sons, and cousins often married cousins. The result was that their skulls were often deformed. King Tut, for example, suffered from such a skull deformation, in addition to "a cleft palate, a club foot (as well as missing bones in his feet), and scoliosis.

3. Lack of Fingernails

When you think of incest, you usually thing of missing limbs, extra fingers, or a lack of teeth. Oddly enough, those things are not the most common signs of incest. However, in some rare cases, children are born with a few things missing.

The incestuous and rather cult-like Kingston family, a splinter clan of fundamentalist Mormons who practice polygamy, has been known to have children that are born without fingernails. That's right, a lack of fingernails on all of their fingers. This could be linked to any number of genetic disorders and conditions, and unless the children were given tests and exams, it would be impossibly to determine exactly the cause. However, we can safely say that the widespread incest in the family has something to do with it.

4. Hemophilia

Several major European royal families were absolutely riddled with incest. Queen Victoria, in particular, saw the negative impact of inbreeding. During the 1850s, Victoria and Albert had a child who had trouble with his blood clotting. While that child, Leopold, did not commit incest with any of his siblings, many of his brothers and sisters did marry into the family, even indirectly, and more of their offspring started to show signs of trouble with bleeding. This is because they were carriers of hemophilia (sometimes called "the royal disease"), a recessive genetic disorder that only became so prevalent because of incest.

Hemophilia plagued the Russian royal family, the Romanovs, and it was fear for the sickly hemophiliac Prince Alexei Romanov, Queen Victoria's grandson and heir to the Russian throne, that led his mother Alexandra to fall under the spell of Rasputin.

Hemophilia happens when the blood does not clot properly. This means that even small injuries like a simple cut, bruise, or nosebleed, can result in a serious loss of blood, and that injuries do not heal correctly. This can lead to infections and even death.

5. Microcephaly



Among Pakistani Muslims, intermarrying within close blood relatives still takes place, and the impact is becoming visible. A recent study shows that about 63% of Pakistanis participate in blood-relative marriages, which is leading to a rise in a condition called microcephaly, where a child is born with an unusually small head. This often means that the brain does not fully develop, either. Mild to severe mental retardation is a major risk. The inbreeding in Pakistani culture means that 1 in 10,000 Pakistanis have this problem, compared to the 1 in 1,000,000 people who have it in the general population.

6. Cleft Palate

King Tut, who was born of incest, showed a surprising number of medical problems when his body was examined, including cleft palate. A cleft palate occurs when the roof of the mouth does not form properly, and is thus left open to the sinus passage. This makes eating, swallowing, breathing, and even speaking difficult.

Modern reports in Kenya and India have also linked this condition to incest, and have determined that this condition happens when the fetus is forming in the womb. Poor genetic diversity in parts of Kenya has led to an increase in this condition, especially in impoverished areas and in small tribes where it's hard to marry outside of a close familial group.

7. Clubfoot



This is another disorder found in King Tut, and it is yet another example of how incest can impact the genetics of children. Club foot describes a broad range of different foot abnormalities, but it generally can be noted by the bones of the foot being malformed, curled under, and misshapen. These conditions are present at birth, and are not terribly uncommon even without incest. However, the condition is more common and is far more severe after generations of incestuous relationships. While it can be treated with splints and braces, it is a condition that sometimes requires surgery and can permanently impact a child's ability to walk. We still don't know to what extent genetics and environment causes combine to create this condition, but we do see that it is passed on from parents.

8. Albinism

Albinism is a condition where your body lacks melanin, a substance that causes your hair, skin, lips, and other body parts to have color. People with albinism tend to have light eyes, pale skin, and near-white hair, even if they come from a dark-skinned heritage. This condition is an autosomal recessive disease, which means that when people with similar genes breed, their children are more likely to have it. Cousins, siblings, and parent/children unions are far more likely to express this type of condition, as evidenced by what happens in small breeding pools.

Puerto Rico, for example, contains small pockets of people that rarely get much genetic diversity. This means that, even if the incest committed isn't super close, there's still enough of a blood relation that the genetic disorder is expressed. Puerto Rico has the highest density of albinism in the world.

9. Asymmetry

In movies, you sometimes see products of incest shown as monsters with horrifying faces. While this is pretty much inaccurate, it does have one shred of truth. Generations of inbreeding can give rise to congenital birth defects, which include facial asymmetry. When you're born, both sides of your face tend to be pretty much identical, including your ears, your eyes, your nose, and mouth. With incestuous offspring, particularly after many generations of incest, we start to see that both sides of the face don't exactly look the same. Eyes can be higher or lower, and may be different sizes. Ears may be uneven, and the mouth may have a slant to it. It certainly doesn't make you a monster, but it's one noticeable side effect of incestuous breeding.

10. Dwarfism

Dwarfism isn't something you see after only one generation of incest, but it has been linked to incestuous breeding over generations. In the 1700s, there was a very close-knit settlement in Pennsylvania called Lancaster, which had problems with inbreeding. Young children failed to thrive, there were issues with infertility, and eventually they saw an emergence of Ellis-van Creveld disease. This disease is associated with dwarfism, as well as the stunting of the extremities and issues with the heart. The eventual emergence of this disease is likely due to a complete lack of diversity in the Lancaster gene pool.

11. Fused Limbs



While extra limbs (polydactylism) and missing limbs do happen with children of incest, it's really not common. In fact, polydactylism doesn't seem to be more common in children of incest, according to some studies. However, fused limbs do seem to be more prevalent in children of incest. In this condition, toes and fingers grow with the skin and flesh around the limbs or digits fused together, making the limbs look webbed or even lacking definition altogether.

The Vadoma tribe in Zimbabwe has a high occurrence of fused limbs in their feet, giving them strange and birdlike toes. This has lead to them sometimes being called "the ostrich people." Because their gene pool is small and because the gene is both dominant and common, the trait lives on.

12. Infertility

The children produced from incestuous unions are not always viable. Either the fetus fails to thrive, or the children are stillborn. In this way, incestuous relationships are often infertile ones. However, even if you do manage to have a child through incest, infertility may be passed on to your offspring. The viability of both sperm and eggs may be negatively impacted, or the reproductive system may simply not function normally. Historically, this infertility has given royal incestuous families no end of trouble, especially given the importance of producing heirs.

13. Scoliosis


This is one genetic condition which is actually fairly common, even without the presence of incest. Scoliosis happens when the spine shows abnormal curvature towards one side of the back. In severe cases, this can impact a person's ability to walk, sit comfortably, and may require surgery or years of corrective braces to fix. A surprising 2-3% percent of American have scoliosis by the time they reach age 16. We also know that this condition can be passed on through genetics. When incest occurs, even if neither parent expresses the gene, they may have a child who has the condition due to the similarity of the parents' genes. Because of this, incest makes scoliosis far more likely to occur.

14. Immune System Disorders

Children born of incest tend to be very sickly. While this may have to do with malformations of the skeleton, muscles, or organs, a major factor is a faulty immune system. In a properly functioning immune system from a non-incestuous pairing, the immune system has a wide range of different alleles that fight off different diseases - the wider the variety, the more diseases you can combat. When you interbreed with a close blood relative, though, the resulting immune system has far fewer unique alleles and can only protect itself from a much smaller set of diseases. This lack of diversity makes a child much more susceptible to diseases, and can effectively stunt the immune system.

We may not fully understand how the body passes on immunity from parent to child, but historically speaking, it's pretty obvious that incest does not help. Our DNA needs diversity in order to build a strong immune system.

15. Cryptorchidism

Guys might find this one a little uncomfortable. Cyptorchidism happens when one or both of your testes don't descend down into the scrotum. Around 3% of baby boys have this condition, and it can cause infertility as well as various reproductive disorders if not treated early. This condition can be linked with various other problems, including Younh-Madders syndrome, which comes with cleft palate and limb problems, as we've previously mentioned. Cyptorchidism can be caused by duplicated chromosomes and has been shown to be more common in children of incestuous relationships.


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