Digit ratio predicts sport performance in female twins

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From the BBC:

A King’s College London team found women whose ring finger is longer than their index finger are more likely to achieve higher levels in sport. The ratio between the fingers has already been linked to traits in men like cognitive ability and sperm count. The study appears online in the British Journal of Sports Medicine. The researchers, from King’s Twin Research Unit, examined hand X-ray images of 607 female twins aged 25-79 from the UK. In each case they measured the lengths of the second and fourth fingers of each hand. The volunteers also ranked their highest level of achievement in a list of 12 sports on a questionnaire. The researchers found women with longer fourth fingers were significantly more likely to be among the top achievers in all the sports listed.

I can’t find the paper online, but I’d like to see it because the news report hints at that the result has a more fascinating twist.

Lead researcher Professor Tim Spector said: “The reasons for these findings are unclear. “Previous studies have suggested the change in finger length was due to changes in testosterone levels in the womb but we also found that finger length was 70% heritable with little influence of the womb environment. “This suggests that genes are the main factor and that finger length is a marker of your genes.” The ratio between the two fingers is fixed before birth and remains constant during life. As this is the case, the researchers suggest that examining finger length may help to identify talented individuals at an early, pre-competitive stage. No specific genes have yet been identified that control finger length. Experts believe it is likely that multiple genes are responsible.

So perhaps the digit ratio is also largely heritable. Can anyone find the study?

14 Comments

  1. Has anyone looked at the digit lengths of autistics?

  2. I think they got stretched with all that knuckle dragging. 
     
    There was a survey that looked at fingers (and toes) for aspies. 
     
    http://www.rdos.net/eng/npf-eval2.php (halfway down the page) 
     
    The toe results were more interesting, but then I am a foot guy.

  3. Maybe it could be a biological but not hereditary factor, kind of like Ray Blanchard’s theory for why men with more older brothers tend to be homosexual more often: antigen reactions in the womb.

  4. http://www.amazon.com/Digit-Ratio-Fertility-Evolution-Trivers/dp/081353030X/ref=si3_rdr_bb_product/104-3656843-9021512?ie=UTF8 
     
    Digit ratio is correlated to how much testosterone the fetus is exposed to in utero.

  5. Given that the sports where the effect is relevant all are running/jumping related, it seems like one hypothesis to look at would simply be foot structure variation (which seems like it might well be correlated with digit length effects in the hands). Granted, the previous research points more towards a hormonal and/or cognitive dimension, but checking out the kinesiology a little more seems like a good idea.

  6. Has anyone looked at the digit lengths of autistics? 
     
    Yes, indeed — there has been quite some research on this. Here’s something from Baron-Cohen and others: 
     
    The 2nd to 4th digit ratio and autism. 
     
    …We found that the 2D:4D ratios of children with autism, their siblings, fathers and mothers were lower than population normative values. Children with AS, who share the social and communicative symptoms of autism but have normal or even high IQ, had higher 2D:4D ratios than children with autism but lower ratios than population normative values. There were positive associations between 2D:4D ratios of children with autism and the ratios of their relatives. Children with autism had lower than expected 2D:4D ratios and children with AS higher ratios than expected in relation to their fathers’ 2D:4D ratio. It was concluded that 2D:4D ratio may be a possible marker for autism which could implicate prenatal testosterone in its aetiology. 
     
    Dev Med Child Neurol. 2001 Mar;43(3):160-4. 
    PMID: 11263685 [PubMed - indexed for MEDLINE]

  7. Also of interest to GNXPers (many of you have probably already seen this – one of the researchers was Trivers): 
     
    Sex and ethnic differences in 2nd to 4th digit ratio of children. 
     
    …METHOD: The 2D:4D ratio was measured from photocopies of the right hand of Berber children from Morocco, Uygur and Han children from the North-West province of China, and children from Jamaica. RESULTS: There were 798 children in the total sample (90 Berbers, 438 Uygurs, 118 Han, and 152 Jamaicans). The 2D:4D ratio was lower in males than in females and this was significant for the overall sample and for the Uygur, Han and Jamaican samples. There were significant ethnic differences in 2D:4D. The Oriental Han had the highest mean 2D:4D, followed by the Caucasian Berbers and Uygurs, with the lowest mean ratios found in the Afro-Caribbean Jamaicans. The sex and ethnic differences were independent of one another with no significant interaction effect. In the overall sample there were no associations between 2D:4D and age and height…. 
     
    Early Hum Dev. 2004 Nov;80(2):161-8. 
    PMID: 15500996 [PubMed - indexed for MEDLINE]

  8. Razib, is this the study you were looking for? 
    http://www.citeulike.org/user/naturecure/article/655726 
     
    “Heritability was estimated to be approximately 66% for 2d:4d (95% confidence interval 0.5-0.78). These results suggest a substantial genetic contribution to the determination of this hormonally related skeletal ratio in women, which could be more influential than the effects of common prenatal environmental factors. However the current study design does not preclude the possibility of confounding between heritability estimates and unobserved prenatal effects.”

  9. A someone who’s published on digit ratios and sexual orientation, I think the spin on this article is unusually bad. First, to my knowledge, it has *never* been demonstrated that higher levels of androgen reduce 2D:4D ratio. The evidence is still circumstantial. So the Trivers book is either misleading or there’s something I don’t know of. Yes, there are sex differences, measurable at birth, but goodness sakes, there’s much about men and women that’s different beyond prenatal T! There could be a third, unknown factor, which is correlated with higher prenatal T and 2d:4d, e.g., cortisol. Second, the BBC blurb seems to imply that genetics and hormones are independent variables, when, obviously, they may not be.

  10. That rdos site is really out there. 
    If I ever have my own website, I’ll have a banner on it that says “A war on diabetes is a war on diabetics” or something like that.

  11. Second, the BBC blurb seems to imply that genetics and hormones are independent variables, when, obviously, they may not be. 
     
    This is a very important point. Hormones affect the expression of genes, and genes affect the level of production of hormones.

  12. Second, the BBC blurb seems to imply that genetics and hormones are independent variables, when, obviously, they may not be. 
     
    This is a very common error in media discourse. A worse, but related error was uttered recently by 60 Minutes’ Leslie Stahl. During her profile of Michael Bailey’s work on homosexuality, she said something to the effect of: “Researchers have long looked to genes to explain homosexuality, but now are looking to statistics.” (Idiotic emphasis hers)

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  14. As an aside – do dominant individuals in the more closely related apes display a greater ‘ring to index’ finger length ratio than their subjugated companions?

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