Sperm competition

Mostly, people are talking about competition between sperm produced by different  males. In humans, this means women that are into speed dating.

The non-paternity rate is an upper limit to the rate of sperm competition:  in many, probably most cases of non-paternity, the woman has not had sex with two different men in a short period of time.  But the non-paternity rate is low!

So classical sperm competition is insignificant in humans, at least in every population we have any data for.  There are those that argue that back in the  stone age, things were far more crazy [hunter gatherers were highly promiscuous, they say], but they’re utterly full of shit.

Now if you go far back enough, a few million years, things were different.  Chimps are highly promiscuous, and have specific adaptations for sperm competition, for example a protein that causes ejaculate to form a plug.  Humans have a non-working version of that protein, which shows that sperm competition used to matter in our ancient ancestors, but hasn’t for a long time.

Still, a number of genes involved with spermatogenesis evolve quite rapidly.  We know several ways in which selection might favor a lot of change.  One is that sperm cells from a given male compete with each other. The other is sexual conflict: the sperm and the egg have conflicting interests.   An allele that increased a sperm’s chance of being first to the egg would be favored.  On the other hand, it is absolutely vital that egg not be fertilized by more than one sperm, so barriers to over-fertilization must exist. Sperm adapt to vault those  barriers more effectively, eggs evolve better barriers, etc.  It’s a Red Queen situation.

A lot of ink has been spilled about all the special physical and psychological adaptations in humans driven by sperm competition of the first kind.  They don’t exist.

Baker and Bellis wrote a lot of nonsense along these lines back in the 90s, sprinkled with fascinating false facts like 20% rates of non-paternity in Britain.  Loons, both of them.

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143 Responses to Sperm competition

  1. Kazbi bas Tzur says:

    Why do you think humans have giant penises compared to other apes?

    • Humphrey Gorilla says:

      I object to this stereotyping.

    • Richard Sharpe says:

      As I recall, Human females are different from Chimp females and the normal human mating position is different from the normal Chimp mating position.

      I suspect that, as with horses, the distances involved require the right equipment.

    • muhry says:

      Primatologist, Alan Dixson, claims that chimp penis length isn’t much different from humans.

      Here’s his study in which some chimps had lengths of 7 inches or so.
      “Sexual behavior, sexual swelling, and penile evolution in chimpanzees (Pan troglodytes).” http://www.ncbi.nlm.nih.gov/pubmed/8024440

      The main difference is that human girth is greater and a possible reason is that the human vagina is more capacious due to human newborns being about twice the weight of great ape newborns. So, the evolution of a penis of greater girth may be from large vagina’d women preferring a correspondent penis

      • Sansfoy says:

        Sounds like another just-so story. If that were the case, cranium size and penis girth would be correlated. This does not seem to be the case.

    • Endre Bakken Stovner says:

      One theory I’ve heard is that where females choose males (chimps and humans, for example) penis size is greater, but where males monopolize females penis size is much smaller (gorillas). Not my field, so do not know how much there is to this view.

      The theory is explained more closely here: http://www.theguardian.com/science/2010/may/06/women-penis-size

  2. Boris Bartlog says:

    You don’t need sperm competition to explain the large penis, though. Female mate preference could do the job even if a society with monogamy, serial or otherwise. For sperm competition to be relevant, there has to be orgy-style promiscuity, not just women switching partners from one week to the next.

  3. ziel says:

    Along those lines, I never quite understood how this alleged adaptation was to supposed to work in any likely mating environment, but always assumed that was just my own naivete.

    • gcochran9 says:

      You just weren’t invited to the right parties.

      • I think that Greg ought to get out a little bit more. I can believe that misattribution of paternity is rare in central Illinois but I don’t believe that that tells us much about many millenia of human evolution. I do fieldwork with a prosperous group of ranchers in southern Africa, Herero, with an interest in family histories as well as the history of the cattle herds.

        One day early on I was interviewing a lady about her family. She said, in the middle, “Henry, I notice that when you ask about the herds you don’t ask about the bulls. People, you know, are a lot like cattle.”

      • gcochran9 says:

        Henry, lots of different cultures do things that I find disgusting or despicable. Including ours. I still acknowledge the existence and frequency of those behaviors. But there’s no example of a hunter-gatherer population that acts like chimps, or anything close to acting like chimps, which is what you would need to make inter-male sperm competition of any importance.

      • Sandgroper says:

        Henry, is it the Himba who believe they are “God’s cows”?

      • dave chamberlin says:

        I suppose we could follow up Harpending’s point with an HBD discussion on diversity in sizes between populations, but lets’ not. The small amount of information gained won’t be worth the type of commentators we would attract.

      • Sandgroper says:

        I’m not clear on how the Herero fit with the Himba. Interesting people, but none of them seem to behave like bonobos. I don’t see why they should.

      • Sandgroper says:

        The Herero/Himba are herders. In the context, it’s a detail.

      • harpend says:

        I don’t know about the Pacific, but a whole broad belt of central and west Africa is known variously as the Tsetse belt, the matrilineal belt, the infertility belt, and the AIDS belt. The Herero are at the southern end of it: they are basically matrilineal belt people who picked up cattle when they moved south and are trying (the men are at any rate) to become Masai or something like that.

        The Himba seem to be kind of poor Herero and the Tjimba their even poorer relations. They ware almost as cattle-crazed as Herero.

      • Sandgroper says:

        That’s as much as I’ve been able to figure – that the Himba are kind of poor Herero, same religion and inheritance laws, but a lot of difference in cultural detail. Handsome people, but probably the worst dancers I have ever seen.

      • little spoon says:

        “One day early on I was interviewing a lady about her family. She said, in the middle, “Henry, I notice that when you ask about the herds you don’t ask about the bulls. People, you know, are a lot like cattle.”

        And then-

        ” I can believe that misattribution of paternity is rare in central Illinois but I don’t believe that that tells us much about many millenia of human evolution. ”

        Yeah, I guess it doesn’t. I think that if you looked at the porn dudes were watching in central Illionois, it would surprise you that their society is not more like the cattle of West Africa. I’d like to know what purpose that kind of common depravity in sexual imagination serves? Allegedly, western civilization is not built upon the practice of daily gang bangs. Yet, fantasies of trying to impregnate one’s wife seem pitifully unpopular compared to fantasies of…errr..other nefarious behaviors, at least in the privacy of a man’s internet browser.

        I’m not sure we have to look as far as the primitive peoples of the world in order to wonder about the more chimp-like mating impulses in humans.

    • Sandgroper says:

      No, the explanation is that you are a perfectly hetero-normative human. The world is full of us.

      Boring, but there you go – reality often is. The evidence that most humans (outside of people like Genghis Khan) have been hetero-monogamous, or at most serially monogamous, for a very long time is pretty overwhelming. Hell, even ‘primitives’ like Aboriginal people living as Pleistocene hunter-gatherers had strict rules about marriage and infidelity.

      People like Trobriand Islanders are really the odd exception, not the rule, and I have to suspect that the reporting on them is at best inaccurate and uncomprehending.

      You can get a feel for this from people who organise ‘swingers’ parties’ and such like – they even get touted by mainstream journalists. The numbers of people they report who actually turn up are tiny. There was some guy here who was trying to tout that infidelity is ‘normal’ and set up some business to ‘connect’ people who wanted to engage in it. Some journalist did a big story on it, like this was going to be the big new modern trend. It wasn’t. After a big ‘You must be kidding’ type readership response, the thing sank without trace.

      • gcochran9 says:

        But at the same time, many people will buy and as far I can tell take seriously total dreck like Sex at Dawn, or Freud, or Kinsey, or John Money.

        In part, this is because the talking classes are disproportionately silly, messed-up people. Probably we need to draft sensible people and force them to write. Some would even have to spend their hitch as professors in the social sciences. Our current approach, taking volunteers, doesn’t work very well.

      • dave chamberlin says:

        I had some hippie friends back in the day who thought they should be in “open relationships.” Surprise surprise, they ended up emotionally damaged. As a whole people have an enormously distorted view of just how little real life is like soap operas.

  4. So we’re talking about Chris Ryan’s book here right? His ‘free love’ model struck me as out of line with human emotions, all he had going for him was the ‘big balls’ argument. I’d like to see a satisfying explanation for that.

    • Sandgroper says:

      We have small balls compared to other primates.

      • Maybe *you* do LOL!!!1

        Sorry I couldn’t help myself. I think Ryan said the ranking of ball volume/mass was biggest ->smallest: Chimps/Bonobos, Humans, Gorillas…I forget where orangutans fall. Could be wrong. Point is, humans have clearly gone through a genital arms race (biggest…penises teeheehee). That’s Ryan’s strongest point. Seem that the results of said arms race are attenuated by ‘length of time under civilization’, maybe that springs from polygamy under civilization (more gorilla-like).

      • Sandgroper says:

        Hey, I have already reproduced and have the genotyping to prove it! How big do they need to be? OK, I walked into that one.

    • LS says:

      I remember reading that human testes are about the same size, relative to body mass, of the (generally) monogamous gibbon. I’ve been looking for a link to confirm that and came across this blog from 2009 which used a calculation by Ryan that was wrong and there is a correction in the comments. Testes to body size ratio:
      1:373 in Chimps
      1:1000 in Gibbons
      1:1266 for Humans
      1:2114 in Orangs
      1:3280 in Gorillas.

      So gibbons are a little better endowed than humans re. ball size.

      Also note that Ryan likes to give the impression that gorilla testes are internal. All primates have external testes. He says gorilla testes are the size of kidney beans yet his own figures show that they are two-thirds the size of human testes and yet he does not pretend that human testes are the size of one and a half kidney beans.
      Probably not a good idea to think of Christopher Ryan as any kind of expert on all this.

      • Sandgroper says:

        And chimpanzees are much higher than humans in both testicle size/body size and sperm production – did I understand that right?

      • LS says:

        Yes, chimpanzee testes are far bigger than human testes and they have a much higher rate of sperm production too.
        Apparently humans have the lowest daily sperm production rate (per gram of tissue) of any mammal looked at so far.

      • Sandgroper says:

        Thank you LS.

      • Sandgroper says:

        I have put you on my blog list as my expert. It’s not a subject I would normally discuss much, but I might turn up there one day, so…it will just be me, Sandgroper

      • little spoon says:

        Hey, how does sperm competition work for other primates? What are the exact mechanisms?

        In the case of sperm causing a plug, my personal study based on my past love life tells me that a typical young human male wouldn’t want the plug because he’s the one that comes back for the second round after half an hour. Maybe a third round too a little later. And then again in the morning. The plug would mainly just be preventing his own extra sperm from getting to the egg. So, it doesn’t surprise me that it would be more advantageous for a man’s sperm to make no plug rather than a plug which 99% of the time blocks his own sperm.

  5. Sex at Dawn was endorsed by Dan Savage, that’s a point against it as far as I’m concerned. I read the two EPJournal reviews by Ellsworth and I’ve thought about picking up Sex at Dusk but haven’t yet.

  6. RS says:

    > So classical sperm competition is insignificant in humans, at least in every population we have any data for.

    Eh? I thought it was quite low in eg upper-class US Whites, but could get pretty considerable depending on race/class. Admittedly, you’re more likely to be right than me.

    > Humans have a non-working version of that protein, which shows that sperm competition used to matter in our ancient ancestors, but hasn’t for a long time.

    Clearly alternative explanations are at least conceivable. Such as, the female evolved to lyse the plug, so the allele is now useless. Or the vagino-uterine environment changed in whatever way and this allele was not able to adapt to that in due time, so it turned into junk DNA.

    > A lot of ink has been spilled about all the special physical and psychological adaptations in humans driven by sperm competition of the first kind. They don’t exist.

    You’re wrong. Even if nonpaternity is 1%, that is plenty to maintain purifying selection on alleles that counteract it. Especially since the pater is probably someone fitter than yourself — and so, on expectation, your wife and probably even you yourself will direct more care to his offspring than to your other offspring (at least theoretically, though there is some empirical work on this).

    Furthermore, we know men contribute a lot more mutations than women. Surely this is simply because men perform thousands or millions of times more gametogenesis. They could spare both energy AND mutations if they were much closer to female human levels of gametogenesis. So something doesn’t add up, at all. Either nonpaternity is as low as ~1% only for select pops/ pop strata, or the 1% level is quite novel timewise and we haven’t had time to adapt to it very well at all yet.

    • RS says:

      > Especially since the pater is probably someone fitter than yourself

      Probably /a lot/ fitter, else why does wifey risk her neck.

    • RS says:

      > direct more care to his offspring than to your other offspring (at least theoretically, though there is some empirical work on this).

      I didn’t mean that I know of empirical work on cuck offspring. Rather I was referring to the general line of work, which a lot of people have probably heard of, claiming that mothers give more attention to more comely infants and stuff like that. I admit I haven’t read it, but it certainly makes sense.

      • melendwyr says:

        “The same is true of those studies that looks at discrepancies between surnames and Y-chromosomes: they show, unambiguously, that paternal uncertainy has been quite low for hundreds of years in the popualtions studied.”

        Then it’s very, very interesting that human males are so concerned about cuckoldry. I suspect this genetic faithfulness is a relatively modern phenomenon, and likely doesn’t hold in places where modernity hasn’t caught on for as long.

        ” Proponents of this hypothesis talked a lot about the high rate of paternal uncertainty in contemporary societies, but everything they said was proven false.”

        1) Then we should be very skeptical about anything they say, and anything people say about the subject. Yourself included.
        2) Uncertain paternity isn’t quite the same thing as false paternity. You say that false paternity rates in certain populations are low; okay, great. Does that mean women aren’t sleeping around on their husbands, or that they’re doing it recreationally and not conceiving children?

      • gcochran9 says:

        Adultery is more difficult among hunter-gatherers than it is modern societies. No motels. No anonymity.

        Your ideas of when and how to be to be skeptical are idiosyncratic. See how polite I can be?

      • melendwyr says:

        “Adultery is more difficult among hunter-gatherers than it is modern societies. No motels. No anonymity.”

        And yet we have powerful emotional responses to the idea of adultery that look very much as though they are innate. You might be able to argue that they are semi-vestigal, that our very distant ancestors developed those responses to deal with an existing problem and that it mostly ceased to be a problem because of them. But you don’t seem able to provide conclusive evidence of the point.

        Meanwhile, you’re making sweeping claims about human evolution by generalizing from studies whose specific details – like which ethnic groups were examined – you’re not familiar with. While being an advocate of the ideas that different ethnic groups have different trait distributions and historical processes may have major implications for how they’re distributed, no less!

        I’m skeptical about lots of things, but when I’m confronted by specific arguments, I focus my skepticism on the claims being made. If you were parroting the received wisdom, I’d be hammering at its weak points instead.

      • gcochran9 says:

        Look, I never said that adultery was unimportant, or that there weren’t adaptations that guarded against it. I said that every recent survey shows that paternal uncertainty is low: and I know which ethnic group is examined in every one of those studies. I’ve read them all. I understand the technical basis of those studies: they are, as I said, solid as a rock.

        Mostly I was talking about sperm competition, which occurs only a subset of paternal uncertainly, likely a pretty small subset. I said that these studies, along with our knowledge of the details of relevant adaptations in other mammals that do have sperm competition, strongly imply that sperm competition is insignificantly important in humans, at least in every group examined so far.

        And that’s that.

    • gcochran9 says:

      Read what I said. Cuckoldry is not the same thing as sperm competition.

      • melendwyr says:

        It’s certainly true that it’s not the same thing, but modern human lifestyles don’t eliminate sperm competition as a factor, merely reduce it.

      • gcochran9 says:

        There is no reason to think that sperm competition was more common in the past. No evidence, anyhow. Certainly not during the last few centuries, with Europeans: in that case we know that remained at the same low level over those centuries. There’s no evidence suggesting that it was more common 10,000 or 50,000 years ago. When you look for the clear-cut adaptations to sperm competition that you see in chimps or baboons, humans don’t have them.

      • melendwyr says:

        “There is no reason to think that sperm competition was more common in the past. No evidence, anyhow.”

        That we haven’t entirely lost traits that look very much like they developed to deal with sperm competition can reasonably count as evidence. You’ve established that it’s much less an issue with humans than it is with some of our distant relatives. That’s not quite the same as showing that it’s nonexistent. Logic indicates that it’s a minor but real issue.

        One of the most interesting and informative methods of understanding the world is to look closely at situations where different lines of argument and evidence seem to support different conclusions. If you discard alternatives because you’ve found a single line of argument that you think is solid, you miss out whether you’re right or wrong about your point.

        I’ve heard assertions about valid paternity like yours, and I’ve heard many other incompatible claims. I have no idea what strengths or weaknesses of any of the involved research might be, no way of checking them for blind spots in their assumptions or failures in their methodologies. And I’m very aware of how easily initial tests can lead to erroneous conclusions. (Remember, human-Neaderthal interbreeding is impossible, so we should discard claims that say otherwise and stop investigating. Right?)

        Human cultures seem intensively concerned with the possibility of cuckoldry, and I’ve heard many claims that it’s biologically innate. Since sperm competition is a major issue with some of our similan cousins, it might persist as an issue with us even in the face of its diminishment as a real concern. It might well have shaped our evolution even though not significant in historical times.

      • gcochran9 says:

        The recent genetic studies are solid as a rock. The only non-paternity cases they wouldn’t detect would be those involving your identical twin. If they say it’s 1-2%, that’s what it is. The same is true of those studies that looks at discrepancies between surnames and Y-chromosomes: they show, unambiguously, that paternal uncertainy has been quite low for hundreds of years in the popualtions studied. It might be different in groups we haven’t looked at – but there is zero positive evidence right now. Proponents of this hypothesis talked a lot about the high rate of paternal uncertainty in contemporary societies, but everything they said was proven false.

        If you look at the unarguable stuff, physiological adaptations for sperm competition – I don’t think there’s any evidence at all.

        The idea is around because some people have written about it, not because there was ever any logical case for it. Sure, sperm competition occurs in many mammals, but so do lots of other patterns that don’t exist in humans.

        Nothing wrong with taking a look at the idea, but it’s never had any decent support.

        If you want, I could come up a with a new theory every week that A. uses a pattern that actually occurs in mammals and B. has some surprising and anti-intuitive social implication. Particularly if I get to make up shit.

        What we have is that a number of people have talked about it, written about it. But that’s not evidence.

    • little spoon says:

      Maybe it was overall more advantageous for sperm competition not to work. I would guess that those kinds of features are the least likely to be accidental- as in not directly selected for. We have things like sickle cell anemia that are not directly selected for (of course) but advantageous because they are linked to something else. Or we have vestigial things that seem to no longer serve any purpose. But something like losing the ability to have sperm competition over the last few million years makes me guess that it was directly advantageous not to have this ability.

    • Lesser Bull says:

      But the non-paternity rates and the sperm competition rates aren’t the same thing. We’re talking about a woman having sex with different men in very short order.

      • melendwyr says:

        It doesn’t have to be that short. Within a day or two under normal conditions, more in ideal. It all depends on the timing. I know human females have lost the clear external indications of ovulation, but I can’t help but wonder if there aren’t strategic behavioral changes, even totally unconscious ones.

      • Sandgroper says:

        You mean the fact that no one can observe fairies at the bottom of the garden, and there is no evidence that they exist, does not mean they are not there?

      • melendwyr says:

        No, I think there might be behavioral changes that we haven’t been canny enough to notice – as in the case of birth control pills altering what women see as desirable in a partner, supposedly.

        There is a difference between “we’ve looked and found no evidence” and “we haven’t looked and know of no evidence”. Before looking, we don’t have evidence of anything. That doesn’t give us cause to deny any possibility; mere ignorance is not justification for reaching conclusion.

      • Sandgroper says:

        But in this case, there is an absolute mass of evidence that for a very long time, humans have exhibited pair bonding, and that the normative state has been monogamy or serial monogamy or polygyny, for a very long time. When good quality, representative data are available on paternity rates, they show that they are so low that you can class this behaviour as deviant, not just now, but going back a long time. Human societies, including hunter-gatherer societies, are not organised like chimpanzee or gorilla groups – nothing like them. Particularly, human female behaviour is nothing like chimpanzee or gorilla female behaviours (which are themselves notably different). No one is saying there are no outliers, but that’s what they are. There is no evidence in humans of special adaptations to deal with sperm competition – the evidence is to the contrary.

        Against all of that, someone comes along and says well, I think that natural human behaviour is to behave like bonobos (having first mischaracterised bonobo behaviour), and that if it doesn’t happen, it is only because the restrictions of modern societies don’t permit it to happen.

        In that case, the person asserting that there are fairies at the bottom of the garden needs to furnish really strong evidence, because all of the accumulated evidence is that we can’t see them because they are not there.

        This is typical of pseudo-science. It gets air play because people like to make out that there is controversy (like de Waal saying that this is “exciting” and that it will need to be “debated over and over again”). The fact that occasionally the scientific consensus turns out to be wrong is paraded as if it demonstrates that the consensus is always wrong, when mostly it isn’t. Barry Marshall’s contention that in many cases stomach ulcers are caused by bacteria was not the consensus for a long time, but when he furnished strong evidence for it, it did not go on being “debated over and over”, it was accepted, and he’s got the recognition to prove it. This is not a case like that – it is a case of the opposite kind – where some unqualified sleaze-bag pushes some ideologically driven theory and cherry picks a few grossly inaccurately portrayed examples to ‘prove’ it, in order to try to persuade modern humans that they are behaving contrary to their nature, and that we will all be wonderfully happy and it will cure all of society’s problems if only we will undergo a fundamental change and all start behaving in the same way as ring-tailed lemurs, when the evidence, such as it is, is that if humans ever do behave like that, they end up really f*cked up.

      • Sandgroper says:

        Sorry, I mean on non-paternity rates.

      • Sandgroper says:

        Note: in this case, the people concerned are not presenting a model like the one that argues that a woman is better off being impregnated by an alpha male and then conning some beta male into investing a lot in caring for the offspring, which you could argue based on the evidence might happen occasionally, although not by sperm competition.

        They are arguing for a model which never happens anywhere – that women should mate with everyone, all the time, with everyone sharing parental responsibility. This is a model that doesn’t occur anywhere in primates.

      • melendwyr says:

        The idea that adultery has not been a fundamental motivator of human behavior and custom for all of recorded history and before is the extraordinary claim. It’s the “fairies at the bottom of the garden”.

        If you want to make such a claim, you need to have very strong arguments. You don’t.

      • Sandgroper says:

        It’s not contradictory.

        Imagine that all human traits are not constants – that they follow some distribution. This should not be difficult because it happens to be true for any trait you can think of. Adultery has been observable everywhere, but not by everyone (far less the false bonobo behaviour we are requested to believe in). When you look at the evidence in surnames and Y DNA going back hundreds of years, it is almost astonishing how low the non-paternity rate has been, and how consistent it has been. For most of this time, modern contraceptive methods were unavailable. So adultery has been observable for a very long time, but actually at a very low rate, throughout history. Until really very recently, cases of adultery tended to be well publicised, so maybe people tended to interpret them as the tip of a non-existent ice-berg.

      • melendwyr says:

        “When you look at the evidence in surnames and Y DNA going back hundreds of years, it is almost astonishing how low the non-paternity rate”

        Adultery is prevented because people are so very concerned about it. They are concerned about it because it is a viable strategy. I’m sure people have been aborting or infanticiding rape-fathered bastards for a very long time, too, but that doesn’t mean that rape didn’t evolve as a strategy among our ancestors.

        In what societies? There are only a few in which there are reliably old surnames.

      • Sandgroper says:

        British and Chinese, for two.

  7. marcel says:

    I did not have much luck with google, but it appears that sperm competition is not much of an issue for loons, so I don’t know what Baker and Bellis were worried about. Maybe they too had big balls.

    • Sandgroper says:

      Have you ever been to see the statue of Bon Scott in Fremantle? It was all relative – he had normal sized nuts, but he was a skinny little midget.

      He only looked tall next to Angus Young because Ang was 5’1″ at his peak.

    • Sandgroper says:

      If you see wot I mean. Bon was 5’3″ is he was lucky. He was rejected by the Australian army.

  8. RS says:

    A 2006 study examined non-paternity rates from 67 published studies. Non-paternity rates for men who were judged to have high paternity confidence ranged from 1.9% in the U.S. and Canada, 1.6% in Europe, and 2.9% elsewhere.

    This is not enough for purifying selection on alleles preventing getting cucked? Come on.

    The rates value varies according to the population studied:

    United Kingdom:
    1 to 2% in a sample of 1,678 men[7]
    1.3%[8]
    Mexico: 9.8% to 13.8% in a sample of 396 children[9]
    Switzerland: 0.3 to 1.3% in a sample of 1,607 children[10]
    United States:
    A study in Michigan of 1417 white and 523 black children found non-paternity rates of 1.4% and 10.1% respectively.[11]
    A study of 1748 Hawaiian families with 2839 children reported a non-paternity rate of 2 to 3%.[12]
    France: 2.8% in a sample of 362 children

    • misdreavus says:

      Virtually every single time you see rates of misattributed paternity higher than 1-2% in any culture, sampling bias is to blame. Of course people who seek paternity testing and the like are more likely to be cuckolded than the average. Convenience samples tend to inflate measures of misattributed paternity. But the actual rates aren’t much higher in Latin America and west Africa than they are here. This has been discussed before on this blog.

      • gcochran9 says:

        I’ve seen only one survey from West Africa. And I haven’t seen too much from Latin America. More research is needed ! If we had an ideographic language, you could express that last sentence as a single character and end every single journal article with it.

      • melendwyr says:

        If it’s at the end of every journal article, we could just as easily leave it out and permit it to be understood by implication.

  9. RS says:

    What about the distortive effect of the very existence of paternity testing? Most women of an age of fecundity realize that it exists, right? I’m not saying this will have some massive effect but it could be rather significant, say 2x for White pops.

    • Greying Wanderer says:

      Your figures suggest a latitude effect – lowest where paternal investment was most necessary in the past.

      “Even if nonpaternity is 1%, that is plenty to maintain purifying selection on alleles that counteract it.”

      If there’s a latitude effect proportional to the necessity of paternal investment doesn’t that mean the selection process has been on the women?

      • Greying Wanderer says:

        Another possibility re. the different percentages in different groups is it’s an underclass percentage as the reproductive logic isn’t the same.

    • gcochran9 says:

      We have estimates for the average rates over the last few centuries in a number of places, by looking for discrepancies between surnames and y-chromosomes.

      In every case, less than 2% per generation.

      Contemporary numbers, about the same, maybe a little lower.

      Although adoption didn’t happen much in the Western world before the 20th century, I think it probably happened occasionally. It would inflate the non-paternity rate.

      Now, is it possible that sexual behavior is different enough in some population so that sperm competition is significant today, or was in relatively recent times?

      Sure, but nobody has ever found evidence for it.

      • reiner Tor says:

        Maybe I’m wrong but I read somewhere that adoption of strangers was rare, adoption of relatives (like a nephew etc.) was more common. If a guy adopted his sister’s son (his nephew) this would have caused Y chromosome nonpaternity issues without being cuckolded or adopting a nonrelative.

  10. agnostic says:

    Sexually repressed time periods have a greater penchant for titillation, since they aren’t getting the real thing. Academia becomes especially infected by it, as bookish types are hurtin’ even more than the rest. Most folks forget that the squeaky-clean ’40s, ’50s, and even into the early ’60s was the heyday of Freudian sexual psychobabble. Not to mention the Kinsey studies, and the popular reaction to them.

    Since the sexual counter-revolution that began in the ’90s, we’ve seen sociobiology, human behavioral ecology, etc. all get crowded out by evolutionary psychology — AKA nerds speculating about sex. Is the penis shaped to scoop out competitors’ sperm? Do strippers who are ovulating earn more in tips? Does cunnilingus boost a man’s Darwinian fitness? (No: it reduces it by giving him oral cancer, you moron.)

    Seeking an endorphin rush through titillation naturally blunts the ability of researchers to understand anything, or perform basic reality checks. Why bother keeping up with “the literature” whose main function is to titillate nerds?

    So you could be forgiven for thinking that “Darwinian approaches to human behavior” yielded some good insights from the mid-’60s through the late ’80s, capped off by Homicide (Daly & Wilson). There are many counter-currents, but they have trouble finding a broad audience. But when that audience is so sex-starved, what do you think they’ll read about — culture as a genetic selection pressure, or DO SYMMETRIC MEN GIVE WOMEN MORE ORGASMS? THE TRUTH MAY SHOCK YOU!

    • syon says:

      “Does cunnilingus boost a man’s Darwinian fitness? (No: it reduces it by giving him oral cancer, you moron.)”

      Yeah, but how statistically significant is the reduction?

      “How bad is this “epidemic” of pussy-eating cancer? According to the Center For Disease Control, HPV may contribute to a whopping “6,700 oropharyngeal cancers in men.” There’s a special asterisk, noting: “Other factors, notably tobacco and alcohol use, may also play a role with HPV to cause these cancers.” In other words, Michael Douglas, who is a lifelong smoker and drinker, may have had HPV present and it may have contributed to his oral cancer, and it may have been helped along by all those years of smoking, too. May.” (http://www.damemagazine.com/2013/06/03/cancer-and-cunnilingus)

  11. Candide III says:

    Judging from data in J.D.Unwin’s ‘Sex and Culture’, hunter-gatherers were highly promiscuous, although not in the bonobo sense (except, perhaps, some ceremonial occasions).

    • gcochran9 says:

      Maybe on Bizarro Earth.

    • Sandgroper says:

      No.

      1. There’s a mistake in thinking that all hunter-gatherer societies must have behaved the same way in everything. Even so, there’s no evidence for high levels of promiscuity. 2. The most recent observable hunter-gatherer societies, not degraded by massive die-off from disease, cultural destruction, introduction to alcohol, etc, were *not* highly promiscuous.

    • piglet says:

      Nah, it’s unlikely that our (recent) prehistoric ancestors were highly promiscuous like chimps for the simple reason that mens’ sexual preferences are the virtual opposite to those of male chimps.

      Male chimps generally prefer older females towards the end of their reproductive lives because under the pump-and-dump strategy they follow it’s best to go for females that have had practice raising babies before or something like that.

      The males in our species seem to have evolved to choose females mainly for long term relationships and try and get as many offspring out of them over the long term. Because of this they have evolved preferences for teenage girls that haven’t started reproducing yet and still have the whole of their reproductive lifespans ahead of them.

      • gordon says:

        Talking about ape sexual preferences, what females do male gorillas go for? Adolescent virgins like our species, mature experienced females like chimps or something different altogether?

      • LS says:

        Basically gorilla males go for any female they can get. They try to tempt females away from the group they are in by showing what big, tough, protectors they are. This can (and often does) include charging a group and killing the dependent offspring. As the group male has failed to protect the offspring the bereaved mother will transfer to the male who killed her offspring – he has shown himself to be tougher than the male she was with.

        Within the breeding group there is a female hierarchy and competition to be closest to the silverback. It is often the females that have to encourage the male to mate and the top female is the most attractive to him and she can even use sex to divert his attention from lower-ranking females. A recent study showed an already pregnant high-ranking female using sex to stop a fertile lower-ranking female from mating.

        So age does not seem to matter to the gorilla male though I suspect the high ranking females are the older, experienced ones.

      • gordon says:

        Don’t the adolescent females have sexual swellings? Is there any evidence that the males find these attractive?

      • LS says:

        I can’t find any evidence that gorilla females have anything other than very slight swellings. In chimpanzees and bonobos the females transfer into their new breeding group when they have a sexual swelling – Goodhall called the sexual swelling the female’s passport to the new group. But with the gorilla it is a single male silverback that is trying to get himself some females and the opportunity probably does not come around very often. Also he is with his females constantly so does not need such a strong visual signal – in chimpanzees and bonobos males and females are often foraging separately and then multiple males are attracted to the sexual swellings.
        So no, there does not appear to be any age preference in gorillas. I would think that adolescent females will be looking for a new male to join if their own silverback is their own father or other close male relative so these may be the main females the males are hoping to impress and lure away. But as the opportunity to breed is only available to a fraction of males I suspect they are not choosy.
        And polygynous males in other primate species only get to breed for a limited time, often only a few years (less than two years in some monkeys), so that is not like human polygynous males. In other primate species with polygyny the females also, therefore, breed with a number of different males over time. Female gorillas can breed in a number of different groups over their lifetime. Getting an adolescent, subfertile, inexperienced, low status female for a few years would not seem to be a particular advantage to a gorilla male.

      • gordon says:

        “Getting an adolescent, subfertile, inexperienced, low status female for a few years would not seem to be a particular advantage to a gorilla male.”

        I was thinking that if gorillas build harems and keep females over the long term that would maybe have similar preferences for acquiring virgin adolescent females with many breeding years ahead of them like the males in our species do but maybe not. Thanks for the info.

      • gordon says:

        *that THEY would maybe have

        Missed a word out.

    • Candide III says:

      @Sandgroper Unwin made a survey of data on around 80 uncivilized peoples around the Earth. Since his book was published in 1934, the data is even older, and he specifically excluded societies which had (had) significant contact with civilization.

      @all Maybe what you’re considering as high levels of promiscuity is much higher than what I thought high, or what Unwin thought high for that matter. He certainly never compared any societies to chimps or bonobos. I don’t remember anything in his survey indicating such levels of promiscuity that sperm competition would be a factor, but very many peoples were recorded to have no concept of monogamy, marriage or chastity. The book is available on the internet as a pdf, you can take a look and judge for yourself.

  12. Sandgroper says:

    From Amazon: “He spent the intervening decades traveling around the world, living in unexpected places working at very odd jobs (e.g., gutting salmon in Alaska, teaching English to prostitutes in Bangkok and self-defense to land-reform activists in Mexico…..”

    For anyone who is not familiar with the part of the world I live in, allow me to opine on something – Thai prostitutes are not likely to pay people to teach them English. Prostitution is not a sought-after profession in Thailand. If you look at construction sites in Thailand, you will likely see young Thai women working as construction labourers – it’s certainly not rare – physically hard, dirty, quite risky work, labouring under a hot sun that burns their very pale brown skin black and wrecks it, in a safety helmet and big steel capped safety boots – they would rather that, or just about anything, than go into prostitution. There is nothing about Thai culture that says prostitution is OK, they just don’t stone people to death for it, just like they won’t stone people to death for being transgendered or whatever the hell they are. The only reason a young Thai woman goes into prostitution is because she is forced into it by someone in organised crime, or because she has no money to live on, no prospects, and there is nothing else she can do to get enough money to feed herself.

    I doubt that foreign guys who patronise Thai prostitutes are looking for deep, meaningful philosophical discussions. It doesn’t take a lot of practice to learn how to say “You want good time?” If a Thai prostitute thinks she needs to learn some English that she didn’t learn in primary school, she’ll pick it up for nothing from some other girls, or from her foreign customers.

    Thais are pretty nice, tolerant people, on the whole, with some very pleasantly aesthetic cultural stuff, not some kind of degraded untermensch to be sniggered at. I don’t have any personal reason to be outraged on their behalf. I just don’t think this says anything very clever or funny about Ryan, even though he evidently thinks it does.

  13. Anonymous says:

    There was a study a few years ago showing that men with high IQs tend to have a higher percentage of functional sperm than men of average intelligence. You think that’s because they have better genes?

  14. Nick says:

    How close in time would encounters need to be for sperm competition to be relevant? IE, one partner Monday, a different one Tuesday? Or one at 8pm, another at 11pm?

    Certainly there are cases of this, but anthropologists usually aren’t involved, I’d imagine.

    • melendwyr says:

      Depends on when the woman ovulated. Healthy sperm can last up to seven days under ideal conditions, probably two or three under more probable ones. The first one to fertilize the egg shuts down competition completely, but if no egg is present, the overachievers will hang around for a while. Which one makes it in is probably a matter of chance.
      Isn’t there a hypothesis that a subset of women follow the evolutionary strategy of mating with as many potential fathers as possible, then exploiting the goodwill of the many men uncertain about their paternity?

      • little spoon says:

        “Isn’t there a hypothesis that a subset of women follow the evolutionary strategy of mating with as many potential fathers as possible, then exploiting the goodwill of the many men uncertain about their paternity?”

        What fraction of the populace does this hypothesis apply to?

      • gcochran9 says:

        There are lots of dipshit hypotheses in this world.

      • harpend says:

        A number of tribes in Amazonia have the idea that a child has multiple fathers, and they do exactly like other primates, i.e. get the “fathers” to do them and the kid favors.

        There is too much loose talk here about what “humans” do based on humans in modern industrial societies.

      • melendwyr says:

        little spoon: “What fraction of the populace does this hypothesis apply to?”
        The same fraction that the “Who’s the Daddy?” advertisements for genetic testing are aimed at, I presume.

      • little spoon says:

        “A number of tribes in Amazonia have the idea that a child has multiple fathers, and they do exactly like other primates, i.e. get the “fathers” to do them and the kid favors.”

        Then their behavior is rational given the premise of what they believe. If we were able to do gene splicing very precisely for humans and combine sperm from different men so that a child ultimately was the offspring of multiple men at once, then it would make sense for all the fathers to invest in the child, and if this somehow happened, I think we would see multiple fathers agreeing to all contribute to the child’s upbringing.

        However, that is not the same thing as the evolutionary strategy of mating with multiple men on purpose to be able to lead multiple men into believing they are the father and then extracting resources based on those men’s uncertainty. In that scenario, the men hope to be the child’s father but they are not sure or they are simply cuckholded.

        Supposedly some societies don’t even get that there is a link between sex and pregnancy. How do they believe anyone is a father at all at that point? In their minds, does father mean only a man who helps raise a child?

      • Sandgroper says:

        Aboriginal people understood the connection between sex and pregnancy, and they are supposed to be dumb.

  15. Anonymous says:

    Fwiw, here is a study showing why people believe cuckolding is a serious issue. Women basically go for more attractive men during their most fertile period, expressing disinterest in their own less-handsome partners.

    The idea being that women are likely to get their genetic material from a guy too high-value relative to her to be interested in her long term. And then she pawns off the responsibility of raising it onto a long-term partner, presumably of equal or lower value than her, to shoulder the burden of raising the kid.

    http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1559901/

    • little spoon says:

      Generally, the lack of sperm competition would favor this more attractive lover, right? (I’m assuming the sperm competition thing in the case of primates favors the first guy in) Because the woman would be sleeping with her long term partner earlier in her cycle and the in the middle of it hankering for the more attractive dude. So if the first man’s sperm cannot block the second, the woman can conceive a child with the handsome lover.

      Wikipedia says-

      “Greater choice and variety of mates increases a female’s chance to produce more viable offspring.[2] However, multiple mates for a female means an individual male has decreased chances of producing offspring”

      So, if that is true, it would seem that it was favorable in humans for the female choice in variety of mates to remain effective and not easily blocked by any male.

    • Sandgroper says:

      We all know the theory. The fact that, in practice, in the modern industrialised world (nod to Henry) no more than a trivial percentage actually do it (and the numbers are consistent going back a long way), should not be allowed to get in the way of a titillating headline which is of virtually zero practical relevance.

    • Greying Wanderer says:

      “here is a study showing why people believe cuckolding is a serious issue. Women basically go for more attractive men during their most fertile period, expressing disinterest in their own less-handsome partners”

      In what environments would that work though?

      I can see it working in environments that required very little paternal investment – which imo is why you might expect to see higher levels of non-paternity among the welfare underclass (although even there I’d say (anecdotal) it was mostly accidental due to relationship overlaps) – but in environments where very high levels of paternal investment were needed I can’t see presenting fathers with children that didn’t look like them as being anything other than a very bad idea.

      If that was so then the stronger selection pressure in those kind of environments might be on the females to be monogamous *despite* any ovulatory urges they might have and if that was so then the men would have less need for any sperm competition traits and the frequency of those traits might go down.

      Also in many parts of the world there have been some pretty extreme cultural restrictions put on women to prevent them following those ovulatory urges which might also lead to a reduced frequency of sperm competition traits among men in those regions.

      Based on personal experience I think once upon a time it was true and that layer still exists underneath but it became less true since whenever high paternal investment became necessary so there’s kind of a recessive r-type layer underneath and a dominant K-type layer on the surface and they conflict (hence the resultant combination of low levels of non-paternity and high levels of bodice-ripping romance novels).

  16. JayMan says:

    Poor Jesse Bering… But then again, “mainstream” evolutionary psychology is growing pretty batshit.

  17. j3morecharacters says:

    Not all cuckoldry is equal. I know a case where the husband’s sperm was weak and cuckoldry was silently agreed. Since about 15% males have difficulties to fertilize their wives in a rasonable number of years, they may account for a large part of the cuckoldry phenomenon in humans. The actual “real” involuntary cuckolds may be less than imagined. Evolution should have equipped human males to be extra alert to the signs of female betrayal.

  18. dave chamberlin says:

    When Cochran gets me thinking about a subject I often wander off into the internet to flesh out the subject area a little bit. This time I went to amazon books and read the reviews on the two books Sex at Dawn and the book intended to counter it Sex at Dusk. Cochran linked to the wiki reference on Sex at Dawn in his opening comment. I have to agree with Cochran that the best selling book Sex at Dawn which hypothesizes that hunter gatherer groups commonly shared sex partners is pure bullshit. I guess you can ignore evolutionary fundamentals when it comes to writing a psuedo-scientific book that is bound to be a best seller because it is about sex. Males do NOT share their mate, they commonly kill or drive away competitors, Bonobos are the exception to the rule. But as we all know sex sells and the complex boring truth doesn’t. I have no interest in wasting my time reading either of these books. But as I mentioned once before in another thread checking out the amazon reviews of books you are considering reading is a great way find the ones worth reading.

    • Sandgroper says:

      From what I could see, Lynn Saxon is a serious scientist who has been trying to do a good job debunking ideologically driven rubbish.

      I think probably the less I say about the other geezer the better. None of it would be complimentary. I won’t be reading anything he writes, ever.

  19. Julian says:

    This reminds me of a theory mentioned in Paul Ehrlich’s book “Human Natures” that the shape of the p8nis may be to scoop out existing sperm.

    • Sandgroper says:

      Before we were Homo erectus, maybe. Suggesting that might say something relevant about human nature after another 2 million years of evolution could be stretching it a bit.

      Not that I’m suggesting Paul Ehrlich was ever wrong about anything, you understand.

      “we cannot pretend that race has any biological significance” – Please, no. That’s why so much is being invested in medical genetics – because none of it has any biological significance.

  20. RS says:

    > Supposedly some societies don’t even get that there is a link between sex and pregnancy. How do they believe anyone is a father at all at that point? In their minds, does father mean only a man who helps raise a child?

    I haven’t heard that, myself. I heard of a society that allegedly made no connection between pregnancy and particular episodes of sex. But they knew you had to not be a virgin.

  21. Patrick Boyle says:

    When reading these comments one should remember that the majority of these intellectual blog commenters are quite conservative sexually. This is a very restricted range of human males.

    I first saw, what I presume to have been sperm competition, when I was a kid. We had an unfixed female cat. When she came into season she made a lot of noise and she entertained all the toms in the neighborhood. They swarmed around her and serviced her hour after hour.

    I never saw anything like that before, but I’ve seen it many times since – at various orgies. After the second divorce I dated a lot, and many of these women were enthusiastic and adventuresome. If you just ask them, you will find that there are quite a few women interested in group sex where they are the only female. In their private musings many nice women want to be the ‘center of attention’.

    The CDC says that the lifetime average number of sexual partners for the average American male is only a little more than six. That’s heterosexuals of course. Gay man operate on an entirely different sexual plane. Therefore many men who comment here, you should remember, don’t get out much.

    If there are wolves on Wall Street, there are also plenty of bonobos in the San Francisco.

    • dave chamberlin says:

      I recall the biggest meanest tom cat in the neighborhood getting first crack and damned if all the kitties didn’t look like him. We moderns have to take ourselves out of the picture of thinking about sexual behavior of our distant ancestors. Why I strongly lean towards one male killing or beating the snot out of anyone trying to make the beast with two backs with his women has nothing to do with my morality and everything to do with survival fitness. How many times and in how many ways has Cochran explained to us that any gene or activity that takes a knock on survival fitness doesn’t hang around long.

      • Greying Wanderer says:

        “Why I strongly lean towards one male killing or beating the snot out of anyone”

        Not possible with humans cos humans cheat. It has to be gang-based or someone would just chiv the “alpha” while he slept.

    • RS says:

      I’m no paragon, and not one to moralize anyway (deonotologically), but this is probably inconsistent with the persistence of high-level civilization. Actually it’s even more the talking of it, especially broadcast, than the doing of it, that is inconsistent.

    • Greying Wanderer says:

      “We had an unfixed female cat”

      low paternal investment

      .

      “but I’ve seen it many times since – at various orgies. After the second divorce I dated a lot, and many of these women were enthusiastic and adventuresome.”

      contraception -> non reproductive sex

      non-reproductive sex == paternal investment becomes irrelevant

    • Sandgroper says:

      I realise this might come as a shock, but the majority of modern humans don’t even live in America, let alone SF.

      If you are twice divorced, that puts you in the minority, even in America.

      I am aware that the 1960s happened in SF. They didn’t happen everywhere.

      I understand that on her tour of China, Mrs Obama is going to focus on the importance of education. She thinks she needs to tell 1.3 billion Chinese that education is important. It sounds like she doesn’t get out much.

    • misdreavus says:

      “If there are wolves on Wall Street, there are also plenty of bonobos in the San Francisco.”

      This quote made me laugh so hard, for all the wrong reasons. Bonobos indeed…

  22. RS says:

    > Virtually every single time you see rates of misattributed paternity higher than 1-2% in any culture, sampling bias is to blame. Of course people who seek paternity testing and the like are more likely to be cuckolded than the average.

    Agreed. Rates are much higher when you study men harboring strong suspicions. But that Michigan study claimed ~1.5% for Whites and ~10% for Blacks. If they used two different methodologies or missed obvious confounds, they are pretty dumb, but I’m not gonna chase the paper. Anyway if it is true, it may be anomalous, as Cochran is usually right, and states that

    We have estimates for the average rates over the last few centuries in a number of places, by looking for discrepancies between surnames and y-chromosomes. In every case, less than 2% per generation.

    • gcochran9 says:

      That study showing ~10% parental discrepancy for blacks in the US is from 1961. It can’t be very good, technically.

      Maybe the rate is different in blacks than it is in whites: certainly the rate of illegitimacy is much higher. You don’t know until you look. Time for a redo.

      • RS says:

        Yes, thankfully I was not yet born in 1961, but I know mankind was still only a half-promising child by that year. They had most of modern physics under wraps, faced up manfully to the hereditarian mainspring of Western and human destiny, purchased large amounts of Mozart recordings, and were headed for the moon landing, but that is small potatoes after the 2003 kinetic intervention in Iraq and crafty dispersal of its one solidary institution, followed up by the ‘World War G’ and ‘World War T’ kulturkampfen here at home, and John Rawls’ eminently pragmatic advances in political theory. By now the word techne and its derivatives can no longer do justice to our level of civilization.

      • gcochran9 says:

        Today we can accurately sequence billion of bases, then they could only look at blood groups. for many questions, you don’t even want to look at data from 2005.

  23. Lesser Bull says:

    Does this mean that gang rape was rare? Or just that in scenarios where gang rape occurred, the victim surviving to bear and raise a child to adulthood was an unlikely outcome?

    • Greying Wanderer says:

      “Does this mean that gang rape was rare?”

      I think regions where high paternal investment was necessary would likely be different from those where women could feed their kids on their own and paternal investment wasn’t necessary.

  24. Anonymous says:

    Very off topic, the a recent NY Times piece for Mr. Cochran:

    http://www.nytimes.com/2014/03/23/magazine/the-scientific-quest-to-prove-bisexuality-exists.html?ref=magazine&_r=2

    Could bisexuality be possibly caused by an infectious organism as well?

  25. RS says:

    > Read what I said. Cuckoldry is not the same thing as sperm competition.

    Hopefully I didn’t say it was, but maybe my spiel wasn’t crisp. So read this if you want.

    In what fraction of cuckoldries do you suppose the husband had a pretty fair (counterfactual) chance at getting the fertilization instead of the illicit lover, thus averting the cuckoldry (I’m assuming no externalities) — ? Would you take 0.2 as conservative? It’s pretty hard to guess at, since ovulation may cause the wife to seek the lover, and she may retain his semen better. (Conception need not be rapid, but it can be.) Those are just random ideas I’ve heard ; I wouldn’t lean back on them for a thousand bucks. But cryptic ovulation must have some purpose(s), or purpose(s)-in-reserve. So must female orgasm, also pretty unique to man (lol), which someone proposed might promote semen retention/uptake/whatever.

    If you accept 0.2, and cuckoldry taxes the average man’s fitness 2%, then the total number of ova/zygotes ‘at issue’ is 2% * (1 + 0.2) = 2.4%. Being 1.15x more victorious in sperm comps than the average man would then be a fitness premium of 1.15 * 0.024 * 0.2 = 0.55%. 1.07x more victorious, 0.51%. It seems like enough to slowly cause adaptations, perhaps rather complex ones, but probably not very costly ones. (Again, this is conservative, at least in intent.) But I’m not a truly steeped evolutionist ; what do you or Harpending think?

    It is not at all obvious to me that it takes ‘remotely-chimp-like’ non-monogamy to drive significant adaptation on this front. That seems a high standard. Got a case for it? Does an organism (properly, one gender of an organism) typically mount no response to a 2% hit? That is not my understanding. It should mount one, given abundant time to find one that is not pricey.

    Further, I see potential problems with just looking at infidelity and cuckoldry numbers.

    Women cheat at no negligible rate. It sure isn’t chimp-like, but humans are considerably more k-selected than chimps, and better (thanks to intelligence) at setting up liasons disapproved by socio-physically powerful males — so more sperm comp ceteris paribus seems reasonable. If I weren’t dog-tired, I might be able to conjure a third or a fourth point. So a fairly tight correlation between non-monogamy and sperm comp, across species, might IMO have notable outliers, which may well include man.

    Sensing potential limits on the value of fidelity/non-monogamy data, we may turn to cuck data . . . where we risk fallacious reasoning if we want to infer low sperm comp from low cuckoldry : who can say cuckoldry wouldn’t be three times higher if not for extensive and successful sperm comp by husbands? Which they certainly could be carrying out : they have a lot of sex with their wives. I’m told that across species, mostly-monogamous (some cuckoldry), biparental-care birds have a coition frequency fairly proportional (inversely) to the fraction of time they spend in company, ie with the female (and male) mutually guarded from voluptuary sin. Makes sense. (I haven’t actually read the paper or searched for opposing claims.) Since sex can be nonreproductive in purpose (as shown by tons of homo sex done by normal bonobos), this proves nothing about why humans have sex so much, but it should justify major suspicion. I know human zygotes die a lot more than other zygotes, so that’s one reason for the high level of sex, but it seems like a lot after accounting for that.

    • little spoon says:

      Regarding high frequency of sex, please see my comment above-

      “In the case of sperm causing a plug, my personal study based on my past love life tells me that a typical young human male wouldn’t want the plug because he’s the one that comes back for the second round after half an hour. Maybe a third round too a little later. And then again in the morning. The plug would mainly just be preventing his own extra sperm from getting to the egg. So, it doesn’t surprise me that it would be more advantageous for a man’s sperm to make no plug rather than a plug which 99% of the time blocks his own sperm.”

      Is it the case that other primate sperm competition mechanisms are not able to differentiate between sperm from a different male and sperm from the same male? If so, it would seem to me that it was more advantageous to have no competition mechanism even if it sometimes leads to cuckholding

      Also, as for the most societies being intensely concerned with fidelity- it is mainly one gender that is intensely concerned. Just because individuals of one gender wanted it doesn’t mean the trait is actually advantageous for the specie.

      • Sandgroper says:

        “Also, as for the most societies being intensely concerned with fidelity- it is mainly one gender that is intensely concerned.”

        I am obviously living in some weird parallel universe which doesn’t follow the rules.

    • gcochran9 says:

      You might want to check your multiplication. You’re looking to find the increment: you don’t multiply by 1.15, but by 0.15. Let us assume that 2% of kids are nonpaternal. Let us assume that 20% of those cases involve sperm competition. Then the percentage lost to other males (in a sperm-competition situation) is 0.4% . 4 x 10-03 is the maximum you could gain if you had sperm like Superman (more powerful than a locomotive & faster than light). You would also amaze the neighbors with streaks of Cerenkov radiation.

      Now let assume that our hero has particularly competitive sperm, 15% more competitive than average. His sperm win a fair race about 57% of the time (instead of 50%). What does he stand to gain from these noticeably superior sperm?
      A fitness edge of 3 x 10-4. Whoop de do.

    • RS says:

      > Being 1.15x more victorious in sperm comps than the average man would then be a fitness premium of 1.15 * 0.024 * 0.2 = 0.55%. 1.07x more victorious, 0.51%.

      Lol, by my logic being 1.0000x as victorious as the average yields a fitness advantage of 0.48%. Apparently I’ve drooled on my shirt.
      THE……. SUN’LL COME OUT! – TOMORROW!

  26. RS says:

    > A fitness edge of 3 x 10-4. Whoop de do.

    That seems too small. Is there no room for a sane centrism anymore in this country? I’d bet on your L0&05 over mine, but I think something may still be missing. How can a 2% hit not cause adaptation?

    • gcochran9 says:

      It probably can, but much more towards preventing female infidelity than sperm competition. Jealousy exists, indubitably.

      If, for example, your old lady knows that you will knock her block off if she strays, that deters all kinds of paternal uncertainty, not just those involving sperm competition. Your jealousy might also deter other guys from trying – adaptations for sperm competition don’t do deterrence.

      It might also be that there are costs associated with modifying sperm, or with increasing sperm production. Increasing the production rate might increase the buildup of mutations over time. Maybe it would increase the risk of testicular cancer. Etc.

  27. RS says:

    > A fitness edge of 3 x 10-4. Whoop de do.

    I got 7e(-4), but what’s the difference. It’s not a high number.

  28. The fourth doorman of the apocalypse says:

    Slightly on topic, but these people seem to think that sexual identity is not under genetic control:

    http://dailycaller.com/2014/03/19/nobody-is-born-that-way-gay-historians-say/

    Thus, if it’s proven sexual orientations are not innate, much of the scaffolding upon which today’s LGBT movement has been built would begin to crumble.

    I find it hard to believe that selection do not strongly clamp sexual orientation to genetic sex (except in cases where a pathogen or a developmental insult has occurred).

      • Anonymous says:

        Does that mean bisexuals are possibly those who are mildly/half way affected by the same gay causing pathogens?

      • Anonymous says:

        Does that mean bisexuals are possibly those who are mildly/half way affected by the same gay causing pathogens?

        What is the sound of one hand clapping?

        What is the mechanism that allows this to occur where the individual engages in sex with members of both sex?

  29. Sandgroper says:

    The Ryan Ellsworth review of Lynn Saxon’s book is worth reading: http://www.epjournal.net/articles/the-myth-of-promiscuity/

    Or you can go to Lynn’s blog: http://www.goodreads.com/author_blog_posts/4240147-my-name-is-lynn-saxon She skewers them good and proper.

  30. RS says:

    Arguably some of my postulates were quite stringent, though (spoiler) it didn’t make much difference to relax them. Midway through, I cabled the J Conserv Guesstimates to say that this manuscript-in-progress may be a better fit for the J Neoconserv Guesstimates, and then it was back to brass tacks:

    2% of kids are nonpaternal, and I now postulate that fully half the nonpaternals (not 20%) occur under (generally-)’even’ sperm competition…. though intuitively that’s rather liberal.

    Hence 1% of kids are nonpaternal with no sperm competition
    1% nonpaternal following even comp
    1% true-paternal following even comp
    97% true-paternal with no comp.

    2% of zygotes are ‘at issue’ in sperm competition, and Guy Average has 2.0000 kids at home, who each grow up to have 2.0000 kids themselves. Subtract the wife’s genetic material, you have 1.0000 of Guy Average’s genes. Now add cuckoldry : Guy Average’s household kids come from ‘at issue’ zygotes to extent 2% (abstractly speaking), and he wins the sperm competition half the time, so he is 0.0100 cucked in his household but gains 0.0100 from his own illicit adventures across town ; net fitness 1.0000. Captain Supersperm1.15x loses 0.0086 on the home front and gets 0.0114 illicitly, net fitness 1.0028, so he is 0.28% fitter.

    1.0028 ^ 200 generations = 1.75. So after five millennia, Ubersperm’s line is not taking over in a big way, even though it is an overcaste fully isolated from average people (this is an imaginary land). 5,000 years is too long ; some kind of disruptive event such as the PIE invasion, bronze-iron collapse, roman collapse, or industrial revolution, or even something much less massive must probably intervene and just wipe this molasses-slow takeover out of consideration, render it irrelevant. And the assumptions about his sperm were quite flattering — though I meant them to represent amplification of several nice alleles in a certain lineage after perhaps 1500 years, not a quantum leap by some single individual — and again, the other parameters I had now set quite liberally as well. So I’m convinced : the area of study Cochran is deprecating is indeed nonsense, or at best deeply suspect (unless ‘surnames vs Y-chromosomes’ is just a really bad method, but it tallies so nicely with survey data that it probably isn’t).

    The math just doesn’t work.

    I suppose my psychological error was ‘how is an organism, in the long run, going to get sapped 2% and take it lying down!!!’ But that’s pretty dumb of me. This isn’t some static thing that you adapt to asymptotically. Cuckoldry is fitness extraction by an active, intelligent, ‘arms-racing’, self-exerting rival being, of equal or better sophistication. So one should think ‘dynamic equilibrium’.

    • Toad says:

      “1.0028 ^ 200 generations = 1.75. So after five millennia,”

      Why stop at 5,000 years? Lascaux was 17,300 years. Neanderthal co-habitation was 32,000 years. Erectus was 350,000 years.

  31. Greying Wanderer says:

    “Could bisexuality be possibly caused by an infectious organism as well?”

    “Does that mean bisexuals are possibly those who are mildly/half way affected by the same gay causing pathogens?”

    If it is a bug and the proportions of homosexual/bisexual varied between men and women then that might provide a clue.

    .

    “How can a 2% hit not cause adaptation?”

    It did.

    http://3.bp.blogspot.com/-Q-36H-2FJbI/Ty-DiSXk47I/AAAAAAAABCQ/dEGabrgXZts/s1600/burqa-women1.jpg

    • Greying Wanderer says:

      A further thought on that would be when is it more efficient to have a cultural adaptation?

      • Anonymous says:

        Don’t you mean: When is it more efficient to have some behavioral trait be learned rather than hardwired?

        For example, the language facility seems pretty much hardwired, however, the specifics of your language have to be learned.

  32. Greying Wanderer says:

    “Don’t you mean: When is it more efficient to have some behavioral trait be learned rather than hardwired?”

    Yeah, probably.

    .

    “What is the mechanism that allows this to occur where the individual engages in sex with members of both sex?”

    Random guess but if sexual attraction was made up of
    a) visual component
    b) everything else
    and the relative importance of the visual component varied between individuals then if the bug only effected the visual attraction component then its effect would vary between individuals also.

    So if someone was 50/50 in terms of visual component vs everything else then they might be 50/50 in sexual attraction also.

    Although that might also imply their relationships would be very different depending on the gender of the other person i.e. the visual component relationships being more casual sex orientated and the everything else ones being more long-term relationship orientated?

  33. Pingback: Some Fuss Over Sperm Competition | Pop Psychology

  34. Pingback: linkfest – 03/31/14 | hbd* chick

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