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FBS
27-05-14, 16:30
Opposites do not attract

Contrary to the common saying, study after study has shown that, on average, opposites do not attract. There’s little doubt that ‘birds of a feather fly together’: people look for similarities when choosing a partner. Now we know that this is even true at a genetic level.

It is a very short article but interesting to contmplate upon:http://www.spring.org.uk/2014/05/people-choose-spouses-with-similar-dna.php

Angela
28-05-14, 02:12
I'm not so sure that's always the case. Here in the U.S. there's a great deal of intermarriage between different ethnic groups, so there are differences in religion, culture, etc., as well as phenotype and things more related to genetics.

So, I don't know how that would correlate with studies like the one you linked, and others I've seen where, in fact, they hold that physical attraction is greater between related people, which is why incest taboos are so strong.

I do think it's fair to say that the studies show that the more similarities that exist, the greater the likelihood of long term success.

LeBrok
28-05-14, 05:27
It is interesting. We know that nature doesn't like sameness too much. Genetic variety "prepares" population to cope with many extreme and changing environments, so someone "adapted" will always survive, and life goes on.
I couldn't see any numbers in this article to check how strong the effect is. Perhaps it is rather week and could be explained by marriages of people from same town, village, high-school mostly. There is always stronger genetic relation to the people from same location, therefore to the spouse too, than when compared to random people from around the whole country.

kamani
28-05-14, 06:47
My opinion: for best results they have to be the right genetic distance far from each-other. Too close or too far is not best match. The right distance would be something like Italy-England or Italy-Lebanon.

Aberdeen
28-05-14, 09:48
It is interesting. We know that nature doesn't like sameness too much. Genetic variety "prepares" population to cope with many extreme and changing environments, so someone "adapted" will always survive, and life goes on.
I couldn't see any numbers in this article to check how strong the effect is. Perhaps it is rather week and could be explained by marriages of people from same town, village, high-school mostly. There is always stronger genetic relation to the people from same location, therefore to the spouse too, than when compared to random people from around the whole country.

Yes, I think you definitely have to factor in those situations where people live in the same area for generations and usually marry cousins, if only because they're related to everyone within the limited area in which they circulate. However, I have also read about the phenomenon Angela mentioned, attraction to those who look similar to oneself. The main reason that doesn't usually become a problem within families is because we're apparently also programmed to be sexually turned off by the scent of someone we grew up with. Of course, that attraction to someone similar theory does take a hit when one looks at how often people in urban North America marry someone of a different race or ethnicity. Like most things, the whole attraction issue probably has multiple facets.

FBS
28-05-14, 11:39
I agree with all of your opinions, there must be multiple facets to this issue and the study as it is presented is quite vague. But, for me it was quite a shock when I found out that I was distantly related with my father in law according to 23andme, so there might be something into Kamanis' observation.

motzart
09-06-14, 06:31
They sure do in the American South.

Engel
09-06-14, 08:16
They shall marry after their own Kind. So German for me

Echetlaeus
09-06-14, 08:51
Just marry someone you love.

Echetlaeus
09-06-14, 09:38
They shall marry after their own Kind. So German for me


All human beings are the same, we are of one kind.

Yes, we are different from lions for example.

Alan
09-06-14, 11:27
My opinion: for best results they have to be the right genetic distance far from each-other. Too close or too far is not best match. The right distance would be something like Italy-England or Italy-Lebanon.

Thats what I also observed. Of course you can't generalize. There are allot of other factors playing into it, but on average it would be something not too distant but also not too close.
Of course "too distant" and "too close" differ based on the definition.



I will explain why. Not too close is to avoid incest and genetic diseases which come with it. Not too far because of the ethno_cultural, often as well genetic point of view, because people with more similarities in culture or living stylen will likely hold longer together.

These are the main aspects but of course there are other aspects like refresh of your own genetic pool, physical attractiveness which often comes with healthy livestyle and/or beiing successfull which gives the partner better chances of successfull offsprings.

At the end of the day it is too complicated to be explained by few words.

Angela
09-06-14, 16:45
All human beings are the same, we are of one kind.


Very well said, Echetlaeus.

Marrying for love is also a good place to start. :smile: Of course, it has to be said that when culture and attitudes are very different, there will be more challenges. I'm romantic enough to believe, however, that given enough love and maturity on both sides, those challenges can be overcome.

FBS
09-06-14, 20:27
Aristophanes and the myth of the soulmate comes into mind. Is there a message in this myth that we could connect with this study ... Just adding some "lets think out of the box" into the discussion...

Engel
10-06-14, 18:19
I don't think that the notion of soul mate is a myth. Mutual love at first sight is what proves the soul mate theory

Greying Wanderer
14-06-14, 19:38
http://www.sciencedaily.com/releases/2008/02/080207140855.htm

An Icelandic study showed maximum fertility at the 3rd - 4th cousin level of relatedness - so not too close but not too far.

It's one theory about the dropoff in fertility with industrialization and urbanization i.e. people from rural areas where they are 3rd cousins to nearly everyone in the local region moving to cities where there may not be anyone in that range of relatedness in their neighborhood.

(anecdote: my wife comes from the valley my paternal ancestors left 200 years ago.)

FBS
14-06-14, 19:45
http://www.sciencedaily.com/releases/2008/02/080207140855.htm

An Icelandic study showed maximum fertility at the 3rd - 4th cousin level of relatedness - so not too close but not too far.

It's one theory about the dropoff in fertility with industrialization and urbanization i.e. people from rural areas where they are 3rd cousins to nearly everyone in the local region moving to cities where there may not be anyone in that range of relatedness in their neighborhood.

(anecdote: my wife comes from the valley my paternal ancestors left 200 years ago.)

Very interesting study, thank you for posting it Greying Wanderer. Well Kamani was very close with his assumption.

Angela
14-06-14, 19:59
I don't think that the notion of soul mate is a myth. Mutual love at first sight is what proves the soul mate theory

Despite all the naysayers, I do believe in love at first sight. I have to; I was hit by a colpo di fulmine (bolt of lightning, which is how we describe it) myself.

However, to be honest, I don't know if that's "love" in the agape sense, or even a "soul" mate, in the sense of a marriage of heart and mind. I think it's more a question of "attraction"in the way we're discussing it here.

For what it's worth, the man, whom I later married, was from the opposite end of Italy (well, his ancestors were), and on 23andme, for example, I have yet to get a single hit with southern Italians on RF. Nor do we look anything alike, really, other than perhaps that we both look broadly Southern European. On the other hand, on the overall genetic similarity measure (which they've discontinued), he was, and remains, my closest match. So there you go. :smile:

LeBrok
14-06-14, 23:34
http://www.sciencedaily.com/releases/2008/02/080207140855.htm

An Icelandic study showed maximum fertility at the 3rd - 4th cousin level of relatedness - so not too close but not too far.

It's one theory about the dropoff in fertility with industrialization and urbanization i.e. people from rural areas where they are 3rd cousins to nearly everyone in the local region moving to cities where there may not be anyone in that range of relatedness in their neighborhood.

(anecdote: my wife comes from the valley my paternal ancestors left 200 years ago.)
Very interesting and makes sense. After all the longest living and healthiest populations are on isolated islands.

1. Okinawa, Japan
In Okinawa—an archipelago 360 miles off the coast of Japan—you’ll find the world’s highest prevalence of proven centenarians: 740 out of a population of 1.3 million (Okinawa Centenarian Study (http://www.okicent.org/)). Okinawan seniors not only have the highest life expectancy in the world, but also the highest health expectancy: they remain vigorous and healthy into old age, suffering relatively few age-related ailments.

2. Sardinia, Italy
Sardinia is an island 120 miles off the coast of Italy where the men—mostly farmers and shepherds—are particularly long-lived. In fact, just one town of 1,700 people, Ovodda, boasts 5 centenarians (BBC News (http://news.bbc.co.uk/2/hi/uk_news/magazine/7250675.stm)).

3. Loma Linda, California
60 miles east of Los Angeles, Loma Linda is a community that includes about 9,000 Seventh-Day Adventists—a religious group that is significantly longer-lived than the average American. Adventist culture is focused on healthful habits (http://www.aplaceformom.com/blog/secrets-of-healthy-aging/) such as vegetarianism, and warns against alcohol and smoking.

4. Nicoya, Costa Rica
The remote Nicoya peninsula has an inland community in which middle-age mortality is surprisingly low: a man at age 60 has about twice the chance of reaching age 90 than a man living in the U.S. (Blue Zones (http://www.bluezones.com/about/)). They also have the lowest rates of cancer in Costa Rica.

5. Ikaria, Greece
Ikaria is a Greek island 35 miles off the coast of Turkey. Like Nicoya, they’ve got a lot of nonagenarians: people there are three times more likely to reach 90 than Americans are. According to the Blue Zones website, “Chronic diseases are a rarity in Ikaria. People living in this region have 20% less cancer, half the rate of cardiovascular disease, and almost nodementia (http://www.aplaceformom.com/senior-care-resources/articles/dementia-information)!”

Full article: http://www.aplaceformom.com/blog/2013-03-29-where-people-live-the-longest/

Author is looking for causes of longevity in food, climate, religion, etc. The simplest truth might be in the insulation of population from "incompatible" gene flaw of genetically distant populations.
It doesn't sit well with my philosophy of Global Village, but that's what it is.

Aberdeen
15-06-14, 04:54
So it sounds as if the healthiest people, in the genetic sense, are those who marry within their tribe but not within their clan, which would probably have been the norm for most people 2000 years ago.

LeBrok
15-06-14, 07:23
So it sounds as if the healthiest people, in the genetic sense, are those who marry within their tribe but not within their clan, which would probably have been the norm for most people 2000 years ago.
I think for the norm we have to go back to small hunter gatherers tribes. They did it for couple of millions of years.

Aberdeen
15-06-14, 15:59
I think for the norm we have to go back to small hunter gatherers tribes. They did it for couple of millions of years.

I would say that some of the small Paleolithic hunter/gatherer clans probably suffered from too little genetic diversity.

Angela
15-06-14, 17:02
I would say that some of the small Paleolithic hunter/gatherer clans probably suffered from too little genetic diversity.


I would agree with that. The same point was made about the Neanderthals in a recent paper wasn't it?

Even with regard to these isolated island or mountain communities, I think it very much depended on what the founders brought with them in terms of genetic material. There are some relatively inbred such communities which suffer from a whole series of genetic defects, while others are remarkably free from them. The Sardinians, despite the high incidence of longevity, are one such group. The French Canadians are another example; their fertility rates in the early years of settlement were extraordinary, but they also are, relatively, prone to certain recessive disorders.

LeBrok
15-06-14, 18:27
I would say that some of the small Paleolithic hunter/gatherer clans probably suffered from too little genetic diversity.

It depends on environment. If it is steady, you don't need genetic diversity. Genetic sameness is pretty good and suiting static environment. However these groups are less prepared to sudden environmental changes, slow to adapt to them, and in greater danger of dying off than others when changes happen.

Aberdeen
15-06-14, 19:07
I would agree with that. The same point was made about the Neanderthals in a recent paper wasn't it?

Even with regard to these isolated island or mountain communities, I think it very much depended on what the founders brought with them in terms of genetic material. There are some relatively inbred such communities which suffer from a whole series of genetic defects, while others are remarkably free from them. The Sardinians, despite the high incidence of longevity, are one such group. The French Canadians are another example; their fertility rates in the early years of settlement were extraordinary, but they also are, relatively, prone to certain recessive disorders.

Yes, a study of Neanderthal DNA actually suggested that inbreeding and lack of genetic diversity may have contributed to the decline of the Neanderthals. As for French Canadians, there's certainly an issue with inbreeding and recessive illnesses in relatively isolated communities such as those in the Saguenay region. It isn't really an issue in more urban areas and less isolated rural areas, because of immigration over the years, settlers from England and Scotland, and also huge numbers of Irish orphans being adopted by French Canadian families during the Irish Potato Famine. The Irish children were sent to French families because the orphans were almost all Catholics, and mostly grew up speaking French and carrying the names of their adoptive families, but they did inject a lot of new blood into Quebec, even if the Irish peasants at that time were probably quite inbred themselves. There's a big problem with inbreeding and recessive diseases in Newfoundland and Labrador, where most people are descended from settlers who moved there during the period 1400 - 1600 AD - the Bristol merchants were fishing in Newfoundland and even settling there before Columbus, although they were initially very secretive about it, to protect their source of cod. So pretty much everyone in Newfoundland is related to everyone else, except for the small minority who've settled there in the last 100 years or so. And of course the inbreeding of the European royals is a whole saga in itself.

oriental
15-06-14, 22:40
I think those "dwarfs" with short arms and legs all being 4 feet or less tall are inbred offsprings.

LeBrok
15-06-14, 23:14
Yes, a study of Neanderthal DNA actually suggested that inbreeding and lack of genetic diversity may have contributed to the decline of the Neanderthals. As for French Canadians, there's certainly an issue with inbreeding and recessive illnesses in relatively isolated communities such as those in the Saguenay region. It isn't really an issue in more urban areas and less isolated rural areas, because of immigration over the years, settlers from England and Scotland, and also huge numbers of Irish orphans being adopted by French Canadian families during the Irish Potato Famine. The Irish children were sent to French families because the orphans were almost all Catholics, and mostly grew up speaking French and carrying the names of their adoptive families, but they did inject a lot of new blood into Quebec, even if the Irish peasants at that time were probably quite inbred themselves. There's a big problem with inbreeding and recessive diseases in Newfoundland and Labrador, where most people are descended from settlers who moved there during the period 1400 - 1600 AD - the Bristol merchants were fishing in Newfoundland and even settling there before Columbus, although they were initially very secretive about it, to protect their source of cod. So pretty much everyone in Newfoundland is related to everyone else, except for the small minority who've settled there in the last 100 years or so. And of course the inbreeding of the European royals is a whole saga in itself.

Let's listen to other side of the inbreeding story a bit:

Let's take a look at some actual figures to see what the real risks are. Perhaps the best example is the work of Professor Alan Bittles, an adjunct professor at the Centre for Comparative Genomics at Australia's Murdoch University, who has worked on the subject for over three decades and in 2008 conducted a review of forty-eight studies (http://www.perthnow.com.au/kissing-cousins-ok/story-fna7dq6e-1111116504749) from eleven countries on the rate of birth defects in the children of first cousins.
He found that increased risks do exist, but not nearly to the extent that we might imagine. While there's about a 2% risk of birth defects in the general population, first-cousin children have about a 4% chance. Of course, you can phrase that in any number of ways, depending on how you want to spin it. On the one hand, that means that there's double the risk of birth defects in the children of first cousins. On the other hand, 96% of such children are born completely healthy, which is still the vast majority.
What's more, Professor Bittles found that only 1.2% suffered increased infant mortalityrates. Generally speaking, these are marginal increases we're talking about, hardly the sort of guaranteed horrific outcomes that are often associated with inbreeding. But all that shows is that inbreeding isn't as bad as we often think - a statement worth making to be sure, but probably not totally earth-shattering. To that end...

Whole article:
http://io9.com/5863666/why-inbreeding-really-isnt-as-bad-as-you-think-it-is

Also there are situations when encouraging recessive traits proliferation by inbreeding, might be good for population. Alleles for very white skin and lactose tolerance might have received a helping hand thanks to close relationship between people in small tribes or villages. I guess, as long as we skip inbreeding to second cousins not much harm happens.