PDA

View Full Version : Extreme Inbreeding in the UK Biobank



Angela
05-09-19, 18:08
That's parent/child, full sibling, grandparent/grandchild, and uncle/niece level. As we didn't need to be told, it's extremely bad for the offspring.

See:
https://www.nature.com/articles/s41467-019-11724-6


"In most human societies, there are taboos and laws banning mating between first- and second-degree relatives, but actual prevalence and effects on health and fitness are poorly quantified. Here, we leverage a large observational study of ~450,000 participants of European ancestry from the UK Biobank (UKB) to quantify extreme inbreeding (EI) and its consequences. We use genotyped SNPs to detect large runs of homozygosity (ROH) and call EI when >10% of an individual’s genome comprise ROHs. We estimate a prevalence of EI of ~0.03%, i.e., ~1/3652. EI cases have phenotypic means between 0.3 and 0.7 standard deviation below the population mean for 7 traits, including stature and cognitive ability, consistent with inbreeding depression estimated from individuals with low levels of inbreeding. Our study provides DNA-based quantification of the prevalence of EI in a European ancestry sample from the UK and measures its effects on health and fitness traits."


The numbers are very low, thank goodness, although I do think the actual numbers might be a bit higher. This is an upper economic group we're talking about and probably these children were adopted and had/have no idea of the circumstances of their conception, while the available data says that it is more present at lower quintiles.

When we're talking about parent/child, especially, it's really disgusting and is no doubt child abuse on the part of the biological father.

Uncle/niece marriage is still permitted in the Near East I think, and repeated first cousin marriage over hundreds of years could bring the inbreeding co-efficient up to this level. Not a good idea, imo.

See also:
https://www.newsweek.com/extreme-inbreeding-uk-biobank-health-impact-1457359

"The team found people there were a host of negative health effects associated with extreme inbreeding. They had a shorter stature, reduced cognitive ability and lower fertility. They also had reduced lung function and, overall, appeared to have a 44 percent increased risk of disease of any kind, in comparison to the general population."

"Researchers said there are a number of limitations to their study. Generally, people who submitted their genetic information to the biobank were healthier than average and have a higher level of education: "Highly inbred individuals who suffer severe health consequences may be less likely to participate in a study such as the U.K. Biobank," the authors said in a statement. "Therefore, our estimate of the prevalence might be too low."

"They found the prevalence of extreme inbreeding was one in 3,652 participants. Estimates for extreme inbreeding in England and Wales—gathered through police reports of incest offences—is one in 5,247."

So, as one would expect, it's not always reported. Plus, not all child sexual abuse by a relative doesn't always result in offspring.

davef
05-09-19, 23:52
Grandparent to grandchild???? Gross!

Adding the effects of inbreeding plus the advanced age of the parent doesn't bode well for the offspring

Angela
06-09-19, 00:45
One of the ways in which Game of Thrones was very unrealistic (aside from dragons, etc. :)) was in the depiction of the daughters of the hermit north of the wall. After three to four generations of extreme inbreeding, i.e. father with daughters, then with his grand-daughters by his daughters then great-grand-daughters, they would have been gibbering idiots.

Look at Carlos II, the last Habsburg ruler of the Spanish empire, the product of repeated first cousin and uncle/niece marriages, after a few generations...

https://farm9.staticflickr.com/8062/8269452002_15a64f0f40_z.jpg

His parents, Philip and Mariana, were uncle and niece, and all eight of his grand-parents were descendants of Joanna and of Philip I of Castile.

He was "short, lame, epileptic, senile and completely bald before 35, always on the verge of death but repeatedly baffling Christendom by continuing to live."[4] (https://en.wikipedia.org/wiki/Charles_II_of_Spain#cite_note-FOOTNOTEDurant196325-4) In his case, the so-called Habsburg lip (https://en.wikipedia.org/wiki/Prognathism#Mandibular_prognathism_(progenism)) was so pronounced he spoke and ate only with difficulty, did not learn to talk until the age of four or walk until eight. "

So much for the benefits of keeping the bloodline "pure".

The French weakened their own royal bloodline by intermarrying with them, imo, as did the Medici.

An occasional first cousin marriage is one thing, but over and over again for generations?

Joey37
06-09-19, 02:56
Yeah, total unrealistic portrayal of inbreds. The Habsburgs were really into uncle-niece matings, too.

Yinwang888
09-09-19, 12:58
"one of the ways GoT was unrealistic"

Lol

bicicleur
09-09-19, 14:07
I guess after several generations of inbreeding, you can produce geniusses as well as idiots.
Unfortunately it is much infintely more easy to create idiots than geniusses. And that is what happens.
Same for mutations in physical traits.

Tamakore
05-12-19, 10:56
It's surprising that pharaonic Egypt lasted for over three thousand years given the pharaohs' tradition of extreme inbreeding. This inbreeding has been confirmed by recent studies. The mummies of pharaohs show little variation in height, an indication of inbreeding. The mother of Tutankhamun was the full sister of his father, according to aDNA studies, and Tutankhamun's wife was his half-sister. Even the Greek (Ptolemaic) pharaohs continued the tradition of brother-sister marriages being the ideal way to keep the royal line pure.

Angela
05-12-19, 16:08
I think there were breaks in the chain, Tamakore, when a new dynasty would come in. Plus, I know that in Polynesian societies, where the royals were also sister and brother, defective children were sacrificed to the gods. Perhaps the case was the same with the Egyptians.

As for the Ptolemies, I don't recall anything in the histories about physical deformities, but by the end a lot of them were mad as hatters.

Tamakore
06-12-19, 02:38
I think there were breaks in the chain, Tamakore, when a new dynasty would come in. Plus, I know that in Polynesian societies, where the royals were also sister and brother, defective children were sacrificed to the gods. Perhaps the case was the same with the Egyptians.

As for the Ptolemies, I don't recall anything in the histories about physical deformities, but by the end a lot of them were mad as hatters.


Yes, 30 dynasties, so a dynasty lasted about 100 years on average, but I still find it surprising, even if they selected a child not obviously flawed, that enough pharaohs were at least semi-competent. The proportion of disastrous pharaohs can't have been high enough to make Egyptians question the whole dynastic system, and wonder whether these rulers really were living gods.

Egypt's pharaonic history must surely be the longest lasting dynastic system on record, beating even China's imperial system, which lasted about 2,200 years.