Well, yes and no about evolution here

Prehistoric humans avoided inbreeding as they knew of its dangers at least 34,000 years ago, a study has found.
They developed surprisingly sophisticated social and mating networks, and deliberately sought partners beyond their family, research suggests.
The findings could explain why modern humans proved more successful than other species, such as Neanderthals, that did not avoid inbreeding.

We’ve always got this problem here.

OK, we can agree that they’ve found outbreeding. We can also agree that out rather than in breeding increases reproductive success over the long term. Super. But this doesn’t mean that they knew. It just means we’re descended from those who did this. That is, outbreeding increases reproductive success over the long term.

We’ve also got other intriguing little bits of evidence. Children raised together seem not to – on average of course – go on to have children or even really to date (the communal dormitories of the kibbutz are one piece of evidence for this). Genetic siblings not raised together don’t seem to have the same internal barrier. The occasional stories (occasional because the basic set up itself is rare) we hear of siblings pairing up into a family producing more children tend to be of those not raised together.

Our end result being that we tend to pair up with people who are genetically close to us but not that close. Part of that may well be just geography – until very recently most of those around you would have been second, third, fourth cousins. But the against sibling mating seems to be something innate – although it comes from being reared as if in the same household, nurture rather than actually genetic.

This doesn’t require anyone to know. Sure, maybe they did but the proof of the outbreeding isn’t proof of the knowledge, we can derive it just from other things we know about human behaviour.

25 thoughts on “Well, yes and no about evolution here”

  1. Yes the fact that it just feels disgusting to think about sex with someone you grew up with, or your children etc, makes it obvious to me that it’s instinctive rather than some knowledge derived from having seen the effects.

  2. If only we had some examples in modern peoples of the effects of marrying cousins for several generations.

  3. It’s the same reason tiger cubs raised alongside lambs (or whatever) generally don’t eat them when they get older.

    There are some things you instinctively don’t do. Shagging and killing those closest to you being a long-term bad idea for your genes.

  4. “Chris Miller

    If only we had some examples in modern peoples of the effects of marrying cousins for several generations.”

    Most of the Isle of Wight?

  5. Britain’s vibrant communities of Muslim peasants from Pakistan, Bangladesh and Africa seem to have shrugged off evolutionary restraints about incestuous marriages.

  6. @Andrew C

    Oi: I’m from the Island- and I have three sisters. And no, none of that went on.

    Although there were rumours at my high school of one girl playing around with her brother.

    Strangest thing I ever heard was of a student (called Dan Ackroyd, oddly) who fucked a VCR.

  7. Strangest thing I ever heard was of a student (called Dan Ackroyd, oddly) who fucked a VCR.

    Bwahahaha that’s brilliant… now I have to dry off my keyboard, thanks.

  8. Dongguan John,

    Bwahahaha that’s brilliant… now I have to dry off my keyboard, thanks

    I hope that means a spilt beverage.

  9. Although there were rumours at my high school of one girl playing around with her brother.

    You’ve just jogged my memory: we had a girl like that in our school, too.

  10. They always say that Tasmanians made great secretaries, the extra fingers made them faster typists and their brothers always got them to work on time.

  11. So Much For Subtlety

    We can also agree that out rather than in breeding increases reproductive success over the long term.

    For various definitions of outbreeding. Most species have an optimal inter-breeding distance. If you think of trees down the side of a mountain, those that are closest are probably too closely related. They will not be robust enough when it comes to disease. But those too far away will have evolved in a slightly different micro-climate. The soil may be different. So you need another tree that is just far enough away to be non-kin but close enough to share a substantially similar environment.

  12. “If only we had some examples in modern peoples of the effects of marrying cousins for several generations”: how about the Frankfurt ghetto and its habits? I cite the Rothschilds, a notably gifted family.

    Maybe it depends not only on the inbreeding but also the quality of the stock that you are inbreeding from. And I dare say the effect is different over a couple of hundred years rather than a thousand years.

  13. I worked as a supply teacher on the Isle of Sheppy, and used to joke that you couldn’t get the kids to count on their fingers and toes as they’d all get different answers

  14. So Much For Subtlety

    Andy in Japan – “I worked as a supply teacher on the Isle of Sheppy, and used to joke that you couldn’t get the kids to count on their fingers and toes as they’d all get different answers”

    You know, I don’t want to be rude, but I can’t help but notice you now work in Japan. Some people can be so sensitive.

    dearieme – “how about the Frankfurt ghetto and its habits? I cite the Rothschilds, a notably gifted family.”

    How talented have the Rothschilds been after the first generation? However when it comes to breeding dogs, once you have a trait you want, you usually interbreed for a little while – most often backwards son-to-mother – to make sure it stays around.

    On the other hand the Japanese Imperial family has been inbreeding for going on several thousand years and it does seem to have done them a lot of harm. Drooling idiots until they stopped recently by all accounts.

  15. “How talented have the Rothschilds been after the first generation?” Lots of talent, as far as I can judge. For example, Victor Rothschild became an FRS in 1953. You got many FRSs in your family?

  16. That it occurs is not proof that it is an exercise in intellectual decision making. Male whitetail deer migrate out of the family group at age 18 months. I assure you they are not intellectually sophisticated.

  17. Bloke in Costa Rica

    So that’s John Square, Pellinor and me all from the IOW. Small world.

    Roppers and their cousin-fucking antics now have them statistically over-represented in the UK in the Sloth Fratelli production stakes by something like 15-to-one. Yay diversity!

  18. Bloke in North Dorset

    “The number of babies born with birth defects in Bradford is nearly double the national average, research conducted in the city has shown.
    The study found this was largely because of marriages between first cousins in the Pakistani community.

    http://www.bbc.co.uk/news/uk-england-leeds-23183102”

    If even the Beeb is prepared to publicise the problem you know you have a problem.

  19. So Much For Subtlety

    dearieme – “Lots of talent, as far as I can judge. For example, Victor Rothschild became an FRS in 1953. You got many FRSs in your family?”

    You might be surprised! He must have been very talented. Because he started working as an academic in 1950. That is a very short time to acquire so much distinction.

    Especially as the rest of his life looks a lot like a rich, idle, dilettante with no particular drive. Although an awful lot of money and all the right connections. So he got the best education that money could buy. He had Communist leanings – being good friends with the Cambridge Five and sharing a flat with two of them – so naturally he went into Intelligence in the war. In his case not so much dropping into Occupied France as dealing with sabotage in Britain by German agents. Yeah. Me neither. Not that I would think money and influence would get you elected.

    But more to the point, his family had stopped marry each other by that point. The last of his direct line to marry a cousin was his grandfather or great-grandfather?

  20. @ SMFS
    The late Lord Rothschild was part of the reason that we are not part of the 1000-year Reich and Jacob, the current Lord Rothschild, is acknowledged to be brilliant by those who do not like him. I am not a fan of Jacob, Lord Rothschild who is/was a dilettante but it is *your* problem if you do not not think that he is highly intelligent.

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