Thursday, December 2, 2010

Loving hands, or 'go finger!'

Remember the Fickle
Finger of Fate?

WARNING:  This message contains adult content (along with something that purports to be 'science').  Digital discretion advised.

Well, we often hear that someone with loving hands is a good lover.  This can be taken both literally and as a figure (or finger) of speech.  The structure of hands isn't often thought of as a sexual attribute.  But maybe that has to change.

Not long ago Holly posted about the finding that Neanderthals were sex-obsessed thugs, based on the length of their finger bones, which indicates apparently how much exposure they had to testosterone in utero.

Now, to add to the complexity of the sexual finger is a story in the British Journal of Cancer about male finger configurations and the risk of prostate cancer. 
The ratio of 2nd and 4th digit length is fixed in utero (2D:4D ratio), and is sexually dimorphic, lower in men than in women. To date, only one longitudinal study has investigated digit ratio and prostate volume, PSA level and the prostate cancer risk. The ratio (2D:4D) is negatively related to testosterone and related phenotypes, such as sperm counts, and positively related to oestrogen concentrations. Accordingly, digit length pattern may act as a proxy indicator for the underlying prenatal testosterone levels. We therefore investigated this in a large case–control study of prostate cancer to explore whether there is any association between hand pattern and prostate cancer risk. 
That is, men whose index finger (2D) is longer than their ring finger (4D) were a third less likely to develop prostate cancer than men whose ring finger was longer.  But on the right hand only, not the left.  (Handedness even in sex!)  And, the previous study mentioned is the "Korean Cohort study" of 366 men, which found a negative association between digit ration and PSA, a measure of prostate cancer that is notoriously not terribly sensitive

As the BBC sums it up,
Being exposed to less testosterone before birth results in a longer index finger and may protect against prostate cancer later in life, say researchers at the University of Warwick and the Institute of Cancer Research.
Does this mean that if you are at high risk of prostate cancer, you're also a sex-obsessed rapine thug?  Or, does this mean that Neanderthal men all had prostate cancer? Have our noble investigators thought (yet) about getting a grant to give DREs (digital research exams, that is) to prisoners convicted of sexual crimes?  When will DRE results be admissible evidence in sexual abuse trials or preventive surveillance?

So this study is based on two assumptions -- one, relative finger length is indeed a reflection of testosterone levels during the development of the hand, and two, embryonic testosterone levels in fact influence risk of prostate cancer sixty or seventy years later. 

However, neither of these assumptions is tested by this study.  The study itself even says, cautiously enough, that digit length ratio "may [our italics] be a proxy indicator for prenatal testosterone levels." And the authors write that other adult diseases have been associated with uterine hormone levels.  The implication being: Thus, why not prostate cancer? 

This is on the nearly silly side, another use of research funds that probably shouldn't.  In addition to the issues we mention above, more than half of men have the Fickle Finger trait (wait, does this mean that the other 1/2 of men are not sex-obsessed? Impossible!  Who ever heard of a man who was not sex-obsessed?), yet the risk of clinical prostate cancer even by old age is only about 150 per 100,000 men.  Indeed, just as with PSA testing, the Finger Test could lead to a lot of screening in the Long Fingered, that could, like PSA testing, cause more morbidity and problems due to intervention than it solves. That's because most males of elder years have some prostate cancer, and most of those lesions never progress to a clinical stage before something more serious (and fatal) intervenes.

Of course, on the positive side, a glance at the hand is less embarrassing than a real DRE (digital rectal exam), or a PSA test to look for prostate cancer.   It may be as useful, at least in terms of risk.  It's a lot cheaper.  Of course the PSA testing companies are likely to resist this current interpretation. And with similar disinterest, what do the investigators say?  "We need a lot more research" (of course).

It all goes to show that even since our ancient fossil ancestors, women should be doing a size test on the guys they date, rather than just casually holding hands--and be prepared for what he might be want to do!  He may want his hands all over you....but it may be in his genes, so to speak, and how could he be blamed??


  1. Wow, so my left hand (shorter 2D:4D) is gonna get prostate cancer. Bummer.

  2. What does it mean if your middle finger is really long and extended compared to the others that naturally flex toward the palm?

  3. Whatever it is, Holly, I'm going to get it too. But apart from having to worry about that, I'm pretty sure it's a sign of brilliance, too.

  4. Hey, you girls must have cut an important lecture in your anatomy or Sex class. You don't even _have_ a prostate! So, while you have to keep your eyes on the guys to have your defenses ready, if you get prostate cancer you should ask your parents about things they must not have told you.

    More worrisome is what you will get instead of prostate cancer. Or does the Digit Test show that you're an unsuspected _female_ predator?

  5. Well, my left hand (the testosteroney one)is definitely the more attractive of the two.

    I suppose this is more "asymmetry" that my osteopathic "doctor" will want to cure by vibrating my hips with her vibrator.

  6. ....or he (she?) will suggest that a prostate implant (and an associated wardrobe change) is the best course of therapy.

  7. Maybe if the finger's long enough then a self-DRE will be possible. Not nearly as embarrassing.

  8. You mean your 2D = your 4D? I don't think that can happen. I think you have to be one or the other.

  9. @Anne: it's confirmed then: I'm an alien!

  10. Clearly, this study has far-reaching implications.

  11. Not to take anything away from the interesting one hand versus another story that you've all be discussing, but add this to the mix (which use, if I remember correctly, average ratios from both hands)... homosexual women have been found to have lower 2D:4D ratios than heterosexual women (Williams et al. 2000 "Finger length patterns indicate an influence of fetal androgens on human sexual orientation." Nature. 404:455). And apparently homosexual women who identify as "butch" have lower 2D:4D ratios than those who identify as "femme" (Brown et al. 2002. "Differences in finger length ratios between self-identified 'butch' and 'femme' lesbians." Archives of Sexual Behavior. 31(1):123-127).

  12. After decades of work, there clearly seem to be genetic influences on sexual preference, and it makes sense and fits some data that this would involve sex hormone components. The idea that preference may be there from birth is consistent with uterine effects.

    And this could have something to do with organ behavior and somehow perhaps even prostate cancer (one can think up scenarios, such as cell division rates, or prostate gland size).

    But even granting that, which would be of interest in its own right, one really would want to know the fraction of sexual preference that is predictable by these digital tests. Is it some kind of vague distributional difference, where the mean values differ even with some statistical significance, but the distributions mainly overlap?

    So we'd need to know how well the science was done. Likewise, were the studies done in a blind way so the investigator nor subjects didn't really know what they were up to (e.g., so women who had variable sexual preference didn't know what the investigator was looking for and somehow shade their self-description of their preference).

    And if the effect on risk is very small, could it be mediated by something else--say response to diet or something--occurring before puberty (say) so that the effect could be culture-dependent and indirect?

  13. hmmmm
    there must be something sciencey to all of this ratio-nalization, but I just can't put my finger on it...

  14. I am pretty sure that tells us something about your prenatal hormonal environment, OE...