Huh?!
Yep, University of Cambridge researchers tested 77 men and 70 women rowers and adjusted for both experience and height and found that size does matter, at least when it comes to the 2nd and 4th digits of your hands. A longer ring finger relative to index finger suggests you might be more predisposed to rowing faster on an ergometer, if you are a man. Before you dismiss this as digital doodoo, realize that this study isn't the first of its kind. In fact, there is mounting evidence that digit ratio is related to all kinds of conditions.
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| My hand: index appears to be smaller than ring finger |
Digit ratio is defined as the length of the index finger (#2) divided by the length of the ring finger (#4). Men generally have a lower digit ratio than women, i.e., men tend to have longer ring fingers than index fingers, while women tend to have equal length index and ring fingers or longer index fingers. This has been known for a long time (source), but only recently have scientists suggested that this might have something to do with prenatal sex hormone levels and particularly testosterone (source). It also seems to be the case that greater prenatal exposure to testosterone has some consequences in adult life.
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| One of my daughter's hands: very similar length index and ring fingers |
Just in the last decade, researchers have gone crazy with digit ratio research, finding that, for instance, soccer players on 1st team squads had lower 2D:4D ratios than reserves or youth team players and men who represented their countries in sporting events had lower digit ratios than other men (source).
Now the researchers of the present study suggest in their summary that "the relationship between digit ratio and sports requiring high power (physical strength) output in addition to well-developed cardiovascular systems has not been defined." So, they set about fixing this omission in science with a study of rowers and conclude that "digit ratio is a predictor of ability in rowing" and that "fetal testosterone exposure has long-term effects on traits associated with physical power in males". In other words, your ability to row fast may have a lot to do with what sex hormones you were exposed to before birth. But, it only seems to matter for men (in this rowing study). However, another study found that women with a lower ratio may perform better in sports too.
I find this somewhat depressing. First genetic inheritance, now this. It seems increasingly that much of athletic potential is predetermined. I'd like to think that smart dedicated training has more to do with athletic performance than it apparently does. I'm spending time examining training intensity, duration and frequency, when maybe I should be looking at my 2nd and 4th fingers.
Digit ratio research like this has some potentially disturbing implications for state-sponsored athlete development, or for that matter anyone (parents) who wants to enhance the chances of a child becoming a star athlete. Expose the fetus to some potent androgens, et voila, a prodigy in the making. One of the leading 2D:4D digit ratio researchers, Thomas Manning, was asked if there are things parents could do to alter fetal hormone exposure. His response: "There probably is, but we shouldn't even think of trying." (source).
For those scheming in this way, there is a significant reason for caution: there may be an increased chance of prostate cancer (source), heart attack (source) and maybe predisposition to all kinds of diseases (source). On the other hand, apparently a low digit ratio correlates with lower incidence of some forms of heart disease (source).
And, before you look at your own hands--what, you did already?--note that measuring the finger length differences isn't as trivial as it may seem and you are apparently looking at very small differences. In the rowing research addressed here, the hands were measured blind (apparently you can see the hand, but nothing else) and with a special device (Mitutoyo vernier calipers). Other studies use x-rays (source).
Personally, I take all this with a grain of salt. 2D:4D ratio begins to sound a bit like phrenology, physiognomy or chiromancy.
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| Phrenology image from Wikipedia |
And, there is some evidence that 2D:4D ratio is not so much due to the in utero hormonal environment but genetics. One research study of twins found that "heritability was estimated to be approximately 66% for 2d:4d." (source). Another study of twins found that "the best-fitting structural equation model indicated that the contributions to individual differences in 2D:4D are 81% additively genetic..."(source). If 2D:4D is mostly a genetic phenomenon that might address misguided parents doping their fetal offspring, but it doesn't address 2D:4D as a predictor of various traits. That is, whether 2D:4D is epiphenomenal of prenatal hormonal exposure or genetics, may be a moot point for those interested in the associated conditions of low or high ratios.
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