April 16, 2009
Royals Prove Inbreeding Is a Bad Idea
Those jokes about inbred royals might have some basis in fact, according to a new study in the journal PLOS One .
The Hapsburg dynasty ruled Spain from 1516 to 1700, reigning over the height of the Spanish empire. The dynasty ended when the last king, Charles II, who suffered physical and mental disabilities, died without issue despite two marriages. Inbreeding had been thought to play a role in the family’s extinction.
A young Charles II, c. 1673, via Wikimedia Commons
A group of biologists from Spain developed an extended pedigree of more than 3,000 individuals over 16 generations so that they could calculate the “inbreeding coefficient” of the Spanish Hapsburg kings. The inbreeding coefficient is a measure of relatedness between two individuals. Here’s an example:
Take a first-cousin mating. First cousins share a set of grandparents. For any particular gene in the male, the chance that his female first cousin inherited the same gene from the same source is 1/8. Further, for any gene the man passes to his child, the chance is 1/8 that the woman has the same gene and ½ that she transmits that gene to the child so 1/8 X ½ = 1/16. Thus, a first-cousin marriage has a coefficient of inbreeding F =1/16 [0.0625].
The six kings of Spain married a total of 11 times. Nine of the marriages were “consanguineous unions in a degree of third cousins or closer.” There were even two uncle-niece unions (eww). Over time, the biologists calculated, the inbreeding coefficient rose from 0.025 for Philip I, the founder of the dynasty, to 0.254 for Charles II. His inbreeding coefficient–0.254–is as high as that expected from a parent-child or a brother-sister relationship (double eww).
In addition to the high inbreeding coefficients, the biologists cited two other lines of evidence that inbreeding was the cause of the Spanish Hapsburgs’ demise: First, the family experienced a high rate of infant mortality, with half of the children failing to reach age one (compared with 80 percent survival at that time in Spanish villages). Second, many of Charles II’s disabilities and illnesses–short stature, weakness, intestinal problems, sporadic hematuria, impotence/infertility–could be explained by two genetic disorders, combined pituitary hormone deficiency and distal renal tubular acidosis. The probability that an individual would inherit two recessive traits would be extremely low, but inbreeding made that much more likely.
This wouldn’t seem to have much relevance here in the present, except as an interesting side story in the history books. However, the authors note that consanguineous marriages account for 20 to 50 percent of all unions in certain populations in Asia and Africa and reach as high as 77.1 percent among army families in Pakistan. In those families, more than 60 percent of marriages are between first cousins.
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It just shows that the wider the genetic pool, the higher the chances for the human race to survive. Royal families of the past already showed the rest of the world that inbreeding does not work.
Thanks for this post.
Wrong presumption, it is not that simple!
Inbreeding is used by all animal breeders without problems. Like Asprin, too much is bad, but controled use is not harmful, and can be helpful, provided that the common ancestor has no genetic problems.
Genetic errors are passed on when we breed, so our children get them even if the gene is a recessive gene (not expressed in the child).
They likewise will pass the genetic error on to their children. So if any generation breeds with someone who carries the same genetic error (whether they are related matters not), then the double copy can more easily become an expressed gene.
However, if there is no genetic errors passed down from the parents, then no errors were passed down, period, so there is no genetic risk even if they were First cousins or siblings.
You people have to remember, GOD is much smarter than you are.
For millions of years our ancestors lived in small groups that repeatedly inbred becasue traveling back then, was not so easily done. There were no cars you know, and animal husbandry was way off, so they didn’t have oxen and horses to pull wagons, in fact, they didn’t have the wheel they walked, and they didn’t walk that far.
GOD made our genetic make-up very complex. You carry the genes of ALL of your ancestors, and all those genetic combinations work together to keep the human race alive.
Just do the math. Every generation you go back from you, you double the nuber of direct ancestors you have. Two parents, four grand-parents, eight great-grandparents, etc. That’s 5 generations every century, 50 generations each millenium. Do the math and work out how many grandparents you have alive in 1 A.D..
Fools talk about the “Eve”, the first women from whom we all decend, those idiots never did this math. You don’t have to go that far back!
In 1 A.D. every person alive today, has more grand-parents alive than the entire population of the earth.
How is that possible for there to be more grand-parents alive than there were people on the planet… IN-BREEDING, lots of it.
GOD knew the conditions what would exists so he gave us genetic redundancy systems so we’d survive.
So long as you don’t keep testing that system with repeated inbreeding, then like the cows and cats and horses, we’ll be fine.
If you want to marry a relative, then check your common ancestor for any genetic problems and get a DNA test done to see if the two of you have any genetic errors that could cause problems.
Fact is, there is no person on this earth that isn’t your distant relative. The math doesn’t lie.
Breeders use their heads and science to keep their breeds pure and health, if we do the same we will be healthy too.
HI Bill,
I have to disagree with your statement “Inbreeding is used by all animal breeders without problems.”
The truth is that inbreeding has increased the inheritance of many diseases in livestock and pets. Certain lines of the Quarter Horse have to be genetically tested for HYPP, a deadly disease. Many breeds of dogs are at high risk for hip dysplasia, epilepsy, eye problems and more. Yes breeders do use inbreeding, but there are problems and many times the affected animal has to be euthanized.
Don’t forget to the Spanish and French Bourbons. They inbred much the same as the Hapsburgs.
Talk about the eww factor. I did my husbands genealogy. His maternal great grandmother’s family is loaded with close relations. For five generations second and third cousins married. Their parents were second and third cousins as were their parents. I have wondered if this is why his great grandmother had so many health problems.
As for the inbreeding of animals. This is why so many breeds have such major health issues. I had a female and one of her pups. The previous owner bred her to a male where half of the ancestors were the same. She and her son both had hip problems, totally deaf and died of massive heart attacks. Their deaths occurred years before standard death rate for the breed. The mother had several generations of the same sire. They had health problems not normally associated with the breed.
I agree with GK. To say that inbreeding is safe if no genetic problems are present is ridiculous and completely ignores factual evidence, especially as often as royalty tended to utilize it. Genetic problems aren’t like a disease, you can’t just not have them. Just because a recessive gene hasn’t been expressed in a population doesn’t mean it’s not there, and it doesn’t mean it’s safe to marry your cousin. It’s impossible to detail a family history thoroughly enough to account for all the possibilities of genetic mutations in a family tree, and testing for all of them would be ridiculous. In general, one inbreeding slip up won’t ruin a population, but when it becomes a regular occurance, it becomes very unhealthy.
Uncle-niece or Aunt-nephew? Which is more ewwie?
Yep, inbreeding is definitely a bad idea, but I only think so because of the reasons given in the article: it creates less room for genetic diversity, and repeated inbreeding leads to higher chances of various genetic defects.
However, I don’t think it’s a bad idea in any moral sense. Not that I or any of my family are inbred, but I’d think that if (and only if) two people love and want to be with each other, then nothing should stop them from doing so. We’re already moving forward with gay marriage, after all.
All the jokes about kissin’ cousins have a base in reality. Who knew? Genetics seems to be based upon the lucknl of the draw. I am sure with proper testing many genetic problems can be avoided.
Genetic diversity is preferred across Earth’s biomes. Our mutt dog was healthy and lived a long life. Our purebred dog was not so lucky. Given a choice I will always take the mutt.