RELATIVE SUCCESS: Scientists find that third and fourth cousins, when they mate, produce more offspring than more closely related couples, as well as distant ones.
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It is not quite incest. And though it will increase your chances of birthing a healthy baby, it is a bit unorthodox, to say the least. Still, scientists at Icelandic biotechnology company deCODE genetics say that when third and fourth cousins procreate, they generally have scads of kids and grandkids (relative to everyone else).
It has long been wondered exactly how kinship influences reproductive success. Previous studies have uncovered positive correlations, but the biological data has been clouded by socioeconomic factors (such as average marrying age and family size) in those populations in which consanguineous marriage is commonplace, such as in India, Pakistan and the Middle East. The new study, however, was able to shed light on the biological reason for the earlier findings.
Scientists came to their conclusions after studying the records of more than 160,000 Icelandic couples with members born between 1800 and 1965. "The advantage of using the Icelandic data set lies in this population being small and one of the most socioeconomically and culturally homogenous societies in the world," the researchers report in Science, "with little variation in family size [and] use of contraceptives and marriage practices, in contrast with most previously studied populations."
The results of the exhaustive study are constant throughout the generations analyzed. Women born between 1800 and 1824 who mated with a third cousin had significantly more children and grandchildren (4.04 and 9.17, respectively) than women who hooked up with someone no closer than an eighth cousin (3.34 and 7.31). Those proportions held up among women born more than a century later when couples were, on average, having fewer children.
Despite the general pattern for reproductive success favoring close kinship, couples that were second cousins or more closely related did not have as many children. The most likely reason, scientists say: offspring of such close relatives were likely to have much shorter life spans, because of the chance of inheriting harmful genetic mutations.
"With close inbreeding—between first cousins—there is a significant increase in the probability that both partners will share one or more detrimental recessive genes, leading to a 25 percent chance that these genes will be expressed in each pregnancy," says Alan Bittles, director of the Center for Human Genetics at Edith Cowan University in Joondalup, Australia, who was not involved in the study.
Interestingly, one evolutionary argument for mating with a relative is that it might reduce a woman's chance of having a miscarriage caused by immunological incompatibility between a mother and her child. Some individuals have an antigen (a protein that can launch an immune response) on the surface of their red blood cells called a rhesus factor—commonly abbreviated "Rh." In some cases—typically during a second pregnancy—when a woman gets pregnant, she and her fetus may have incompatible blood cells, which could trigger the mother's immune system to treat the fetus as a foreign intruder, causing a miscarriage. This occurrence is less probable if the parents are closely related, because their blood makeup is more likely to match.
"It may well be that the enhanced reproductive success observed in the Iceland study at the level of third [and] fourth cousins, who on average would be expected to have inherited 0.8 percent to 0.2 percent of their genes from a common ancestor," Bittles says, "represents this point of balance between the competing advantages and disadvantages of inbreeding and outbreeding."
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13 Comments
Add CommentCan we say: "worst title ever"?
Reply | Report Abuse | Link to thisCatchy, but offensive?
people need to learn that words are never ever the problem - the title works because the title explains why imbreeding within a certain degree holds biological benefits. get over being 'offended' by words or this century will be a very punishing century on many .....
Reply | Report Abuse | Link to thiskissing cousin
Reply | Report Abuse | Link to thisn.
1. A distant relative known well enough to be kissed when greeted.
And that's how it starts ....
B-)
:^O
I'd say it's probably due to social factors rather than genetic factors: third-cousins would be more likely to have other relatives around to help in child-rearing. Unrelated couples probably have a weaker support system, because chances are, at least one of the couple is not from the town where they live. Having relatives around to help mind the baby would obviously help ensure its survival.
Reply | Report Abuse | Link to thisSome Indian studies have shown more fertility and offspring mortality among close kin marriages when considered maternal uncle nice marriages and marriages among cross cousins up to third cousin category.
Reply | Report Abuse | Link to thisHindus have a gotra-equivalent to genus-generally derived from a rishi-founder[an enlightened soul] of the family ;Manu,the hindu law-giver laid down the rule that sagotris[persons belonging to the same gotra]shall not be married;since the family adopts the gotra of the husband in the Hindu patriarchal society,marriages between children of brother and sister[her gotra changes with marriage] or vice-versa occur due to a literal interpretation of the Manu's law;however in very orthodox brhamin families in north India,marriages are done only if the gotras of both parents on either side are not the same;sagotris shall not marry is perhaps the earliest known genetic prescription in human society
Reply | Report Abuse | Link to thisI didn't see anything about birth control. Could it actually be that they have a lower success rate at birth control?
Reply | Report Abuse | Link to thisThis article does not address the question: what proportion of our brain NEURONS are in use at any one time on average? The article only talks about use of brain AREAS, which is not at all the same as use of the actual brain cells and accompanying axions/synapses etc. Does science have the answer to that question?
Reply | Report Abuse | Link to thisIt's insensitive to label the marriage between cousins as 'incest' especially for the article that everyone in the world can read.. I mean, some countries legalize marriages between cousins, and I feel weird reading this article having parents who are first cousins themselves (and I don't have any health/mental problems).
Reply | Report Abuse | Link to thisI love my "cosuin". We always were best freinds, and loved each other. I didnn't think that was a bad thing, but our 'elders' broke us up.
Reply | Report Abuse | Link to this, and it wasn't just about the sex.
we aren't alowed to see ; or speak to each other anymore, but I think we both would be better off if we could.
We didn't think we were doing anything wrong, as her parents were cousins. I love her and miss her a lot.
Everything isn't right without my best pal. I don't feel guilty about anything, because we loved each other.
we belonged together
I lost my virginity to a third cousin and we had a pregnancy scare with protection so i think its funny i found this article.
Reply | Report Abuse | Link to thisWe hid our relationship from our families for a long time until we had a car accident and my parents had to come get us. Thats when everyone found out. We're not together anymore but our families would be happy if we were.
I remember being so stressed when i thought i might be pregnant worrying about possible birth defects and if i could abort if i had to. Now I kno i worried for nothing.
This is extremely old. But just want to say that the post gives scientific reasoning. First off it specifically says higher birth rate. Meaning take the 3rd cousin take the 8th cousin have them both try to procreate at an even rate and the 3rd cousin will have been more successful. Secondly it explains that miss carriage is less luckily also a reason why more procreation occurs. Because there blood is compatible do to the slight relation to each other and allows the women not to have an auto immune to fight it off causing miss carriage. And that lastly the genetics are different enough to cause healthy children. If you think about it.. with the populations of the human race in its early stages this might very well be what mother nature intended. And everyone saying offended... this is a scientific study.. there not telling you to do this.. or saying anything that should be considered offensive grow up people.
Reply | Report Abuse | Link to thisIt is incest, and there's nothing wrong with it. I know a brother/sister couple as well as cousin couples, it's all fine.
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