inbreeding, digit ratio, and altruism

in his post A pathway to pro-social behavior, peter frost references this article Second-to-Fourth Digit Ratio Has a Non-Monotonic Impact on Altruism in which the authors say:

“We find an inverted U-shaped relation for left and right hands, which is very consistent for men and less systematic for women. Subjects with both high and low digit ratios give less than individuals with intermediate digit ratios.

the subjects were w.e.i.r.d.-ish, btw — university students from granada, spain.

peter comments:

“From one population to the next, digit ratios tend to cluster around different means, perhaps because altruism has been favored or disfavored to different degrees.”

i’m not familiar with those differences (will have to investigate), but i did post this from turkey in a recent linkfest:

“Inbreeding is associated with lower 2D:4D digit ratio”

“We compared the 2D:4D ratios of 122 male and 108 female consanguineous (children of first cousin marriages) high school and university students to those of 142 male and 122 females controls. Across hands and sex, consanguineous parentage was consistently associated with lower, more masculine-typical, digit ratios. Digit ratios were 1.3–1.9 times more variable among the consanguineous group than the control group. While socio-economic status cannot explain the effects seen in our data, we found that lower, more masculinized, digit ratios were associated with lower family income.”

inbreeding leads to…whatever genotypic/phenotypic package that results in lower 2d:4d digit ratios *and* lower rates of altruistic behaviors? dunno. Further Research is RequiredTM.

ftr — i come from a population that has been inbreeding up until fairly recently, and i’ve got a low 2d:4d digit ratio. uh oh.

(note: comments do not require an email. hands.)

16 Comments

  1. 0.89 digit ratio, but I come from a mixed ethnicity marriage and I’m one of those annoying vegan animal rights guys who is constantly worried for others. I guess we’re both exceptions that prove the rule? Whatever the case, I am always interested in new 2D:4D research.

    Reply

  2. http://www.eurekalert.org/pub_releases/2004-10/bis-aft102004.php

    This ”news” above is old but, very interesting also. The exceptionalities of human beings probably to be found in extreme testosterone levels and low testosterone levels.
    Women scientists and women social scientists have above testosterone levels than their non-scientists women.
    But how we could separate the higher testosterone criminals to higher testosterone analytical minds?? Low estrogen levels in criminals with very high testosterone?? This is the pattern to criminals?

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  3. @hbd chick “inbreeding leads to…whatever genotypic/phenotypic package that results in lower 2d:4d digit ratios *and* lower rates of altruistic behaviors? dunno. Further Research is RequiredTM.” Don’t hang me out to dry on this one, but I do have the nagging suspicion that “inbreeding” (and nobody every seems to say how they define that) leads to more masculinity among males, which means outbreeding should lead to less. My evidence is all circumstantial. When I checked my outbred (population running in the tens of thousands) fruit flies the males seemed just as numerous as as male-looking as the optimally bred lines (standard four males and four females selected for each generation). I had a pathologist check the slides. Fame and fortune if he could find a difference, but he couldn’t. On the other hand, their performance in actual number of offspring was reduced.
    I agree. Needs more research. I may have something useful to say in another year or two.
    ftr got a pretty long D4 here.

    Reply

  4. As a male artist with a high digit ratio I find this fascinating. According to these results, you don’t see lower sexual dimorphism in inbred societies, you see manlier men AND manlier women, while places like England and the Netherlands has more Feminine men and more feminine women, essentially a feminized culture. One thought that occurs to me is that a more feminine mindset does have some advantages. You might expect to have more nuanced communication, more creativity, and weaker men physically which could drive them to invent force multipliers.

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  5. @ Sisyphean – “while places like England and the Netherlands has more Feminine men and more feminine women..”

    Not so much the north of England! ;-)

    But in general I agree.

    Reply

  6. My apologies for being off topic, but I found a document online that may interest you. I came across it while searching for “behavioral genetics phrenology,” because after first coming across (a couple of months ago) b.g. being called phrenology I have seen it several more times. So, here is the RationalWiki (as in, I suppose, anyone who does not agree is irrational) entry on Biological Determinism. It is a sort of compendium of the sorts of things that your and related blogs seem to be struggling against. You may find it useful as a specimen collection, or just entertaining. In the past I have considered writing a parody document along this line, but I have been summarily preempted. I am sending a similar/identical comment to several other blogs, this is too good not to share.
    http://rationalwiki.org/wiki/Biological_determinism

    Reply

  7. I broke my hand in a fist fight in high school. It healed a little crookedly. So I have trouble measuring the length of my fingers.

    That’s why I can’t determine if I’m masculine enough.

    That was my right hand. I stuck a knife in my left hand. Same problem – scarring and shortened tendons.

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  8. @Patrick L. Boyle, If you won the fight you’re masculine ; )

    Seriously though, is this a individual-level measure? And how good a proxy is it? I don’t understand why they don’t measure something more direct, like serum levels of testosterone?

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  9. “According to these results, you don’t see lower sexual dimorphism in inbred societies, you see manlier men AND manlier women”

    Arranged marriages based primarily on relatedness should lead to lower levels of sexual dimorphism.

    Reply

  10. It appears that these studies found that more testosterone driven individuals are less altruistic, cooperative and pro-social, which would be true, as we see it with blacks. However, East Asians (who are generally less masculine than Whites) show less pro-social behavior towards out-groups, more so than Caucasians.

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  11. Also, speaking of inbreeding: The tribal behaviors, facial asymmetry and high intelligence of Ashkenazi Jews (the majority of Jewish Americans) are said to be a product of inbreeding, but inbreeding is believed to decrease intelligence.

    Reply

  12. @js – “Also, speaking of inbreeding: The tribal behaviors, facial asymmetry and high intelligence of Ashkenazi Jews (the majority of Jewish Americans) are said to be a product of inbreeding….”

    pretty sure that there hasn’t been that much inbreeding — specifically cousin marriage — in western ashkenazi jews. eastern (russian) i think might be a different altogether. stayed tuned for more on this…one of these days.

    Reply

    1. Seems I remember a study a few years ago that said American Jews by and large are all genetically related as if they were fifth cousins. The Jewish authors took some flack for the study but it seemed sound. Don’t know whether fifth cousins constituted inbreeding for you. Of course that’s their genetic similarity. The epigenetic similarity has to be a lot less or they’d be having a lot more children.

      Reply

  13. @anonymous – “Don’t know whether fifth cousins constituted inbreeding for you.”

    yeah. for the purposes of this blog, “inbreeding” means mating with second cousins or closer. (^_^)

    Reply

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