The Genetic Benefits of Mating Outside Your (Group)

Painting of Charles V, Bernard van Orley (circa 1515–1516)

Science

Written by: m.wilson

When individuals tend to mate within a particular ‘group,’ it increases the likelihood that the recessive genes of the ‘founders’ will (activate) – interact with each other and develop within the couple’s offspring. The founder effect is enhanced when a fraction of that group changes locale, because the potential for these recessive genes meeting up increases. Basically, there is less competition in the area so these recessive genes are being hired for all the work…

“Where’s My Hasenpfeffer!”


Amish people, mostly residents of the Eastern Pennsylvanian region, are said to be in high demand for genetic study because of their intermarriage. Scientists find that the founder effect is very common within the Amish, (descendants of German immigrants), which causes abnormalities such as dwarfism and polydactyly – additional fingers and toes. So instead of the traits diminishing (‘My son John Doe happens to be short’), these genes increase in concentration; grabbing onto each other so they can make things happen.

‘Why doesn’t Harry marry royalty?’ says your auntie M. 

Royal intermarriage has been instrumental over the centuries in matters pertaining to inheritance, diplomacy, legal concerns, etc. (Wikipedia, 2019). Looking back at this history of the monarchy through the lens of science, often provides additional insight into the possible causes of some of their misfortunes and challenges. For example, scientists speculate that Henry Vlll may have suffered from McLeod Syndrome, a genetic disorder “caused by a variety of recessively inherited mutations.” McLeod is both mentally and physically debilitating, which they say, may have caused him to be more punitive towards his wives. However, it is considered a matter of fact that inbreeding caused the downfall of the Spanish Hapsburgs (1516-1700). During the 16-century Phillip ll, (a most regal member of the Spanish Hapsburg dynasty), was generally regarded as a “foreigner” during his marriage to Mary l Queen of England; despite the fact that she was actually his first cousin once removed, (her mother was Spain’s Catherine of Aragon). No children resulted from the marriage of Mary and Phillip ll. He would, however, continue reproducing in later marriages. On the other hand, during the 17th century Charles ll of Spain, the last of the Spanish Hapsburg males, whose inbreeding coefficient was higher than 0.20, was born an imbecile. He had a misshapen head, could not walk properly, was impotent and sterile; and died young at the age of 39. Upon his death, the French Bourbon dynasty would claim power over Spain (Science Daily, 2009).

Charles ll’s inbreeding was the result of “repeated cousin marriage over several generations (Discover, 2009).” It is said that his upbringing only contributed to his mental retardation and hypersensitivity. His genetic disorders had to do with ‘recessive alleles at two unlinked loci: combined pituitary hormone deficiency and distal renal tubular acidosis…’ Needless to say, for some royal families, it could be a good idea to take a refreshing, genetic break from the group.

Cancer Mortality Rate Increases for Latino Immigrants

A recent public release from the American Association for Cancer Research (Nov 2018), stated that the cancer mortality rate is increasing for Latino immigrants. Cancers, such as prostate, pancreatic, and stomach, were the cause of 21% of the Latino death rate in 2016 (AAAS, 2018). Apparently, each generation encounters higher rates of cancer. The risk of lung, colorectal, and liver cancers, has increased significantly in third-generation Mexican-born immigrants, as compared with first-generation Mexican –born immigrants. The study concludes that there is an “overall increased risk of cancer with each generation born in this country (AAAS, 2018).

The report discusses the American lifestyle as a possible cause, and another, the problem of access to healthcare. However, a study published in PNAS (2015) found that the genetic relatedness in Mexican couples is frequently two to three times higher than randomly sampled couples of other ethnicities (including non-Hispanic whites) in the same location.

This rate of genetic relatedness increases to four times greater in Puerto Rican populations, indicating that ancestry correlations of Mexicans and Puerto Ricans are shared at third and fourth cousins (in relatedness). Unfortunately, the propagation of “disease burden” becomes more evident within related environments (PNAS, 2015). More research needs to be done and behaviors certainly exacerbate genetic conditions. However, it seems probable that elevated prevalence of Hermansky-Pudiak syndrome (recessive lung diseases), asthma, and now cancer, have a strong association with genetic relatedness.

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