Human Inbreeding: A better understanding

Unions contracted between persons biologically related as second cousins or closer (F ≥ 0.0156) are categorized as consanguineous. It is very confusing whether children of consanguineous marriages are genetically predisposed to any developmental defects. In my previous article ‘Human Inbreeding: What are the consequences?’ I tried to explain the deleterious effects inbreeding may cause. The articles I read at that time were not very conclusive whether inbreeding is beneficial or deleterious. So, I decided to dig up some more scientific journals to find out the effects of inbreeding.

One article I found, reasserted the former argument that inbreeding does not have any effect on fertility (spontaneous abortions and stillbirths) of women. However, higher rates of neonatal and post-neonatal deaths, and deaths of children younger than 5 years were observed in consanguineous couples. I then thought, does inbreeding affect the fertility of men? A study involving Middle-Eastern Males demonstrated that consanguinity and the familial clustering increased the chances of having infertility problems 2.6 times higher in cases than controls. So, I am thinking even though inbreeding does not cause any aberrant pregnancies, inbreeding does have adverse effects on male fertility and on survival of newborn children.

I have also wondered whether inbreeding plays a role in other diseases. While searching for answers to satisfy my curiosity, I found that researchers who have looked at Middle East and North Africa region have pointed out that in the Islamic Arabs residing in these regions, there is a high prevalence of first-cousin consanguinity. Hemoglobin disorders, inherited metabolic disorders, neurogenetic disorders, and birth defects are also relatively common in this part of the world. One can thus ask a question that may be these diseases can be credited to, at least in part to the inbreeding?

Also, medical professionals have found “significant association between parental consanguinity and congenital hypothyroidism.” Congenital hypothyroidism seems to correlate with the degree of consanguinity—children of first cousins are more prone to than those of second cousins.

Amid all the confusions, it is very well accepted that among genetic disorders, only autosomal recessive disorders are strongly associated with consanguinity. However, there are ample of studies showing that in a population with a high rate of consanguinity, there is a significant increase in the prevalence of common adult diseases like mental disorders, heart diseases, gastro-intestinal disorders, hypertension, hearing deficit, and cancer. Interestingly though, a study in Arab populations, however demonstrated that reduction of overall cancer risk was associated with increased coefficient of inbreeding (F). Both older and younger healthy men had significantly higher F but only women over 30 years of age with higher F had reduction of overall cancer risk. This study showed that being more inbred was associated with a reduction in overall cancer risk by about 25%.

I am not sure what to make of the relationship between inbreeding and cancer but I am certain that in breeding may have adverse affects in humans and it should not be encouraged.

More readings
Examples of inbreeding in humans
Probability of inbreeding


Kobeissi and Inhorn; Health issues in the Arab American community. Male infertility in Lebanon: a case-controlled study.
Kerkeni et. al.; Interplay of socio-economic factors, consanguinity, fertility, and offspring mortality in Monastir, Tunisia.
Saadallah and Rashed; Newborn screening: experiences in the Middle East and North Africa.
Hashemipour, et. al.; Parental consanguinity among parents of neonates with congenital hypothyroidism in Isfahan.
Hamamy, et. al.; Consanguinity and genetic disorders. Profile from Jordan.
Bener, et. al.; Consanguineous marriages and their effects on common adult diseases: studies from an endogamous population.
Denic et. al.; Risk of cancer in an inbred population.



Filed under Evolution, Human Evolution, My Life My Thoughts

58 responses to “Human Inbreeding: A better understanding

  1. Just found a touching article about Human inbreeding

  2. megan

    my mum and my boyfriends mum are cousins and i am pregnant sould i be worried

  3. Hello Megan,
    Sorry for the late response. I suggest you consult your physician immediately regarding your question. However, you may ponder upon a few things just to achieve some peace of mind:
    1. Inbreeding is only harmful when there are chances of inheriting recessive traits. The closely related the partners are, the higher the chances of inheriting recessive traits. So, if your mom and his mom are first cousins, there are higher chances of your baby inheriting the recessive traits. If they are second or third cousins, the chances are lower.
    2. It would be helpful to know if someone in your family have some major diseases. Find out whether anyone in your mom’s and dad’s family have had diabetes, heart diseases, or other serious conditions. You should also do the same for your boyfriend. If you can extend this to as many of your ancestors–grand parents, great grand parents’ families that would be even beneficial. If you find high rates of serious conditions, your baby’s chances of inheriting them become higher.
    3. You may also look at where they can scan your genome and tell you if you are susceptible to any dangerous conditions for a price ($1000).

    I am not a doctor so I think the best thing for you to do is consult your physician about these questions and act according to his suggestions. However, there may be some disease resistant genes in your ancestors and your baby may also have a chance of inheriting those traits. So think positive as well. Hope my comments are of some help. Feel free to contact me again if you have any questions.

  4. I am pregnant with my brother’s baby.

    Should I go on Jerry Springer?

    Does this make me inbred?

    And my mum says this is normal.

    But I am confused.

    What should I do?

    Please reply to my email address

    Thank you.

    • No this does not make you inbred it make your child inbred and please take it from someone who knows first hand it is a good possibility that your child could suffer from seizures and other problems I hope everything works out.

    • Anonymous

      hhahahaha you should go on Jerry Springer. That’s where inbreds like you belong.

  5. Anonymous

    they just mutated

  6. Anonymous

    why/how did you become pregnant with your brothers child?

  7. bill depp

    No, The entire Royal Families of UK and even more so Japan are products of inbreeding, and for far much longer then you and your babies. They have turned out relatively fine with some noted aberrations coming from recessive genes such as the British Royal family and hemophilia The Japanese Royal family are close to being midgets at all under 5 ft., They all are blood relatives for over 2000 years, 125 legitimate monarchs since the accession of Emperor Jimmu (traditionally dated to February 11, 660 BC), including the reigning emperor, Akihito. The Egyptians had lots of inbreeding and the Royal family had some problems as well, the Pharaoh Akhenaten had an elongated stomach and feminine hips. So I would relax and not worry about this at all.

  8. I am inbred. My mom and my dad are first cousin. In they had me and my brothers. Theres is nothing wrong with us. We are just like everybody else.

  9. Scott

    To Anonymous dated November 12th-

    You may well be just like everyone else. Upon more research you will discover that a prolonged heritage of inbreeding will produce problems and not a once in a lifetime occurrence.

    As the author said above, the closer the relation the higher the risk…even if it is a first time affair.

  10. This blog directs quite a bit traffic to my site and has additional and neatly organized links about inbreeding and may be quite interesting to read:

  11. jason

    While the european royal families are inbred (though not as much as some people think) the haemophilia was not caused, nor was it spread by, inbreeding. It was a spontaneou mutation occuring in Queen Victoria. She had one Haeophiliac son (out of four sons), and passed the gene to two of her five daughters. They had haemophiliac sons and grandsons but they would have done so anyway, regardless of who they married. The incidence of haemophilia was not increased by inbreeding.

  12. Anonymous

    inbreeding is disgusting u shud be put down

  13. AI

    Inbreeding is said to be the cause of the madness of Geogre the 3rd of England the goverment had to lock him up and run the country themselves.

  14. Random.

    Hi. My B.F is my dads 2nd cousin but my b.f is younger than me… I was just wondering if i was to ever fall pregnant, would our babies be disabled? I’ve heard people say that they would be but im really curious !!!

    • Comprehenda

      You’re 2nd cousins once removed. Technically. I don’t think it’s considered to be cosanguinous, so you wouldn’t really be comitting incest. Anyway, 3rd cousin marriages result in an increase in fertility, but 2nd cousing marriages result in a decrease (assuming no removals). It ought to be fine, though you should still look at your extended families health to see if there are any genetic disorders – if both you and your boyfriend are heterozygous for a recessive genetic disorder, your children would have a 1/4 chance of getting said disorder. As was said before by the author of this blog, consult your physician, and consider getting your DNA tested to find out how genetically similar you are (because of the way inheritance works, it’s theoretically possible – though very improbable, so much that it most likely will never happen – for two siblings from the same parents to not have any genetic similarity at all). You may not be genetically related, in whoch case their shouldn’t be a problem.

  15. mel

    hi, my mum and her brother had me and i turn out alright also i had a child and
    she turn out alright to. But i think there should be something wrong with me.

  16. Rudy Barkly

    This is hilarious

  17. Aaron

    i come from a long line of pedigree inheretance as im related to the japanese royal family and there is nothing wrong with me. my mother was one of the first people in 100’s of years to marry outside the family and there has never been a case in the family of any problems.

  18. pamala

    look, its a free country, (if ur in the US) although i am utterly repulsed by all males in my family when it comes to sex, who am i to judge? my brothers and i took baths when we were like 2 but thats as hot and heavy as it ever got. i dont know much about it but i do kno that seeing as there has never been any definitive proof that inbreeding is harmful offspring and u cant help who u fall in (love) with, do what ever the hell makes u happy.
    oh yeah i do know that one good thing is if u ever marry a family member, at least u wont have to bother with changing ur last name, lol.

    • Anonymous

      that’s disgusting.

    • Anonymous

      there has been proof that people with the same defective recessive traits can have children with that defective trait being expressed. stop putting on a cover with all that bath stuff stop kissing your brothers and preaching about free love you hippie and go immerse yourself in the scientific world…
      o yea and i do know…. your not funny thats sick you incestual creep.

  19. Concerned

    Okay, my half sister had a baby and my mother and I believe that it was from her father. My mother has the child now. The child has been diagnosed with ADHD and has been on several medications for it but it does not seem to help. I was wanting to know if he could look normal and be a smart 8 year old boy and still be an inbred? Also is there anyway you can test him to find out if he is inbred without his mother or her father’s DNA? I didn’t know if there is some test that would just show up in him that would point to him being inbred? Please help. I have searched and searched on the web but have found nothing.

    • I also would want to know if I were you I do not know if there is a test to see if the child is inbred but if they do a DNA test that will show how close the relation is and that should be enough to let you know I hope that everything works out for the best. Before I go I want to share a story to share with you.My husband’s brother and their first cousin possible bio sister have two kids together and the kids do have metal and physical problems I much like you have searched the web and found nothing so if you have advice please share.

  20. Responses to the comments:
    To Jason: As for Hemophilia, Jason you are correct that it was a spontaneous mutation in Queen Victoria. Since she had the other allele that was functional she turned out okay and so did seven out of her eight children. However, of the seven children that were fine, two were a carrier and passed the hemophilia allele to their children. Hemophilia is a recessive disease; thus even if you have one hemophilia allele, you do not get the disease. The only chance of getting the disease is if you are homozygous for the hemophiliac allele. Since consanguineous marriage was common in the Royal family, the frequency of heterozygotes for the hemophilia allele increased and marriage between the heterozygotes resulted in more hemophiliac children in the Royal family. If you look at the Royal Pedigree, allele frequency increases every generation. Good thing is Queen Elizabeth did not inherit the allele and so her descendants are now fine.

    To Random: As evidenced by the example above, consanguineous marriage does not guarantee that the children of such marriages are disabled. It means that if both the parents of such marriage share a mutation which was in the common ancestor, then the risk of inheriting such mutation is high in their children. In your case, your boyfriend is your third cousin so the chances of your child being disabled are low but still higher than in the population. If I were you, I would get more information about your great-great-grandparent who was your common ancestor and every subsequent family member there after and see if you see any disabilities. If disabilities are common, then you should be concerned.

    To Aaron: dude you are lucky.

    To Concerned: I am not sure whether the ADHD in the child is because his mother got impregnated by her own father. It could be. Recent research has implicated that ADHD can be genetic ( It is possible that the mother and her father share the gene and the baby has both the copies resulting in a ADHD kid. I am not sure why he is not responding to the medications though. There could be many reasons. Since he is a child from a consanguineous marriage, he is inbred but he may be just fine except from the ADHD he has. You can do genetic tests to find out if the has any other genetic disease. Consult your doctor. You can however test which allele he inherited (from his mother or from his father) by comparing his DNA to your mother’s. Since your half sister shares half her DNA from her mom (your mom) and half hers from her dad, the only possible DNA in the child are from your mom and his dad. By comparing your mom’s DNA with his you can figure out which alleles he got from his dad. This is in theory but I am not sure how cost effective it is and I am not sure it will tell you anything. You should still contact the people at the link I provided above and see if they can help you further. Good luck.

    • Mike

      I can vouch first hand that adhd is hereditary lol my (half) brother and i have it, our mother has it and her father as well (unknown as to whom he inherits it from as he’s in his sixties and his parents long since deceased)

      The child may not be reacting to adhd medications because they may not actually have adhd – it’s not as cut and dry as diagnosing a broken leg or missing finger, the child may simply be naturally energetic and (depending on their age) may be showing early signs of a dominant personality by refusing to cooperate with those with authority

  21. Inbalance & Genius
    Extraordinary and inexplicable capabilities can be seen in some people who ‘suffer’ from an apparent inbalance disorder, such as Autism. Is there any known correlation between similar/same group inbreeding and the occurrence of such (mental/perceptual) conditions?

  22. Sultan Mahmoud

    My fathers brothers son & fathers sisters daughter are married (first cousins). They have a daughter. If I marry her will there be any birth defects with our children?
    I have read on the net and found out that in first cousins there is a slightly greater risk compared to second cousins and so on. But my concern is since both her parents are also cousins is the risk increased? Thanks

    • ashok

      Don’t marry her. You would be in second generation of inbreeding. The probabilities of birth defects increase many folds in second generation.

      • Ashamedofheartlesslovescrooges

        You can’t just tell somebody not to marry someone! Yeeash, did you even READ the last 20 essays above? -_-

    • To Sultan Mahmoud Please do not take this in a bad way But dont marry her give yourself and your possible future children a chance to have a healthy and normal life. First cousin and any one that is related shouldnt have kids together it does cause them to have problems. I cannot tell you what to do But please think about it give yourself the chance to love another.

  23. not saying

    My mom came across some information that blew us away. Ill get right to it. A long time ago my grandpa was a product of brother and sister royalty. They also made my grandma. My grandma and grandpa were adopted out but were considered pure blood line. They were considered as still born and kept a secret. My grandma and grandpa met later in life and were dating when she thought that grandpa left for the german war but her adopted parents kept him in hiding at thier home without my grandma knowing he was under the stairs. During this time my grandmas and grandpas biological father came looking for them and my grandma had an affair with him(her father) and they made my mom. My grandma passed away and my grandpa doesnt want to talk about it. My mom has two other sisters that look completely different from each other. I really need to get some sort of genetic testing to make this concrete. What kind of information can be revealed from genetic testing to prove this?….if any. Its all the same dna..right?

  24. It has recently been discovered that my grandson, aged 16, was fathered by my sisters son. Of course the information was explosive since my daughter said that she was raped by some one she did not know. Several years ago he began to have difficulty walking. My daughter was 13 when she delivered him. He was handsome, intelligent, and was simply darling. However he did seem to take a long time to begin walking. After he finally began to walk unassisted, it appeared that he was having pain in his legs; and for years we were told by health providers that he merely needed physical therapy to gain strength in his legs. Around age 7. he began to limp. and had obvious pain.

    The specialist advised surgery to release tension in his leg muscles, which seemed very logical and promising. In the following days one of the specialists came to his hospital beside and commented that if the DNA of the father was known, they could then do further research on this newralogical and genetic condition. My family began to show concereds to the risk that this condition may repeat itself in future relatives. At the time of his surgery neither my grandson nor I knew his father was.

    Months after his surgery it was confirmed who the paternal parent was. I was very upset that my daughter did not confide this information to the doctor. My sister, however insisted that the DNA information of my nephew made no difference since it would not change the outcome that “he has a medical anomoly that will not result in a change of his condition.” I disagreed. Shouldn’t I?

  25. Grace

    Just found out my son’s father is inbred. His mom and uncle are his parents. What are the possible defects in my son? He is only 7 weeks old and so far he seems fine? What should I look out for. I’m super worried. My son’s father is horrified as he just found out the truth himself. Also we were planning on two more children but now we don’t know what to do. HELP!

    • To Grace I would be honest with Drs. about your son.Inbreeding is not safe Im not telling you not to have more kids you deserve to be happy even though this info. was kept from you.But please put alot of thought into having more kids because inbreeding can,will and has caused problems for other kids best of luck

  26. You’re a absolute freak, I hope you die of inbreeding mutations!!!

    • Anonymous

      Hello Alex. It’s time for you to learn some English!! I do understand, it must be difficult for you – a freak mutant!! Leave other people alone.

  27. Marnie

    I’m a new member of a Canadian reformed church so I’m not originally from there but one of the rules they have is that they can’t marry outside of the church. So you have all these people who are getting married to people within the church and so obviously after awhile of doing that you’re going to inbreed. And the result of that is a lot of the kids at my church have these creepy really big light blue eyes and blonde hair. I understand there are people with big blue eyes and blonde hair, but you can tell the difference between someone inbred and someone who isn’t if you put them side to side. Some of them also have really big foreheads and faces. And there is a lot of kids with celiac disease, can’t eat gluten, and all the adults think these things are normal and they don’t think it’s inbreeding. There have been a couple of cases were no one had to change their last name because they had the same one. Is that not disturbing?

  28. Anonymous

    Ok, I don’t care who you are or how you or your kids have turned out because of inbreeding. It’s fucking disgusting. You’re related to that person by blood. Rape is one thing…but consensual sex with a relative? Fucking disturbing.

  29. Here is another article in NYT sort of related in the sense that if there is a rare mutation that runs in the family and causes remarkable phenotype (appearances), it can be somewhat easily detected even after 200 years. If individuals carrying the same mutant alleles produce children, which could be considered inbreeding, the child has a very high probability to inherit two copies of mutant alleles and display the abnormal phenotype. However, the child may not display the phenotypes for other reasons such as epistasis (another mutation masking the effect of the original mutation).

    • Anonymous

      Hello I am married to a man whose parents I found out were first cousins and well my son and daughter I have by this man have mental and slight physical problems is this caused by his parents marrying in the family?

  30. Yousonuva

    What the hell kind of article is this? You researched a bunch of real articles and tossed snippets on here with bad grammar. Stop doing stuff.

  31. fans

    My story is different, my girlfriend and I are not blood related but our her dad and my mom share the same surname in African culture its still forbidden but then South Africa is a free country just the family structure is different and a lot of emphasis is given to family during the cultural part of weddings, but my question is this doesn’t count as inbreeding right?

  32. Torie

    I am married to a guy who’s parents I found out are first cousins. Well my 2 kids I have with him have mental and physical problems would their marrying in the family like that cause my kids problems?

    • Comprehendaloopaflurt

      No, at least not directly. He’s inbred, but you’re not related to him, so it’s not a consanguineous relationship. However, his chances of carrying alleles which have a negative effect is higher, so it may have had some influence. But your children aren’t inbred, though…

  33. wtf

    If a girl became pregnant by her grandfather, what would the likelihood be of their seemingly-normal male offspring to have children with birth defects? & could those children be tested to see if they are inbred or not?

    • Anonymous

      I was wondering if it’s possible to find out if my dad’s great grandfather was his dad. My grandmother was repeatedly raped by her grandfather until the age of 15 when she became pregnant. But “nobody knows” who the father was. My grandmother is dead now & my dad has no relatives.

  34. Pingback: Famous Hollywood Director Defends Incest – Love Who You Want « Samaritans Scalawags Scoundrels Fleecing the Sheep

  35. Anonymous

    I just found out my Grandma had my dad by my grandpa. And I am the product of my dad. And I am fine!!

  36. MathematicalErrorTree

    Leave everyone alone!!!! I came here for novel research (DON’T SAY ANYTHING!!!) and it seems my head isn’t as alien as I thought it was!
    These things could happen anyway, and love is a unpredictable variable in our lives. Do what you have to do, and ignore all the rude and ignorant people (mostly anonymous, obviously – out of SHAME) on the internet, and make sure regardless you give your kids the best life possible.

    😉 MathematicalErrorTree

  37. MathematicalErrorTree

    BTW, rude people who just insulted these probably normal people, you’ve just said a load of things to people and relatives of people who are risking their lives giving new life to the universe. The only life I’ve seen are in the people who are goving constructive advice. User with the lion logo, I doff my hat off to you. AND, next time I see ANYTHING so pig-headed on this site again, I’ll make sure that people out there don’t follow your pitiful example. Rant over, very useful!
    😉 MathematicalErrorTree

  38. Hello.This publish was extremely motivating, especially simply because I was browsing for thoughts on this topic last Saturday.

  39. Anonymous

    So um… My boyfriend is an inbred and he has some problems (he tends to have seizures and has Parkinson Syndrome). We plan on getting married soon, but should I worry about any birth defects?

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