The issue of hand size became a peculiar source of battle and mockery in the 2016 presidential campaign, when then candidate, now President, Trump and Senator Marco Rubio sparred about small hands versus large hands, clearly as a reference to hand size being associated with genital size.
The science behind a more particular hand issue– finger length– is not new. The first recognition of finger size as a sign of other bodily issues dates back to the late 19th century. It continues to be a source of battle between scientists. In the past two decades, over 1400 papers have been published analyzing the significance of finger ratio. Twenty papers have been published this year. In addition, the ongoing finger length feud is related to sex.
A recent article in Science magazine reviewed some of the numerous published studies which look specifically at finger length ratios, and more specifically on index finger (2D) to ring finger (4D) length ratios between genders. This ratio has become known as the 2D:4D ratio, which is calculated by measuring the length of the index finger (2D) in comparison to the ring finger (4D). I’ll give you a few seconds to look at your own hand, and make a rough calculation.
Finished?
Chances are (as so much in population-based studies is, indeed due to chance), if you are female, you may have noticed that your index and ring fingers are about the same length. If you are male, you may have noticed that your ring finger towers ever so slightly taller than your index finger. Many scientists would agree, but some would not. According to some evolutionary biologists, men’s lower 2D:4D ratio is due to higher levels of testosterone exposure as a fetus. And this gender-related ratio is thought to be linked to anything from personality to cardiovascular disease to cancer. Others state that this ratio variation is simply a result of faulty data analysis, poor evidence, and subjective measurement collection.
In 1998, John Manning and colleagues found this finger length ratio discrepancy between genders in children as young as age two years. Research continues in this area, with investigators utilizing varying methods of measurement: photocopiers, calipers, or x-rays. One British study was able to recruit over 240,000 subjects to provide self-reported finger length data. The differences they found were extremely small: the 2D:4D ratio in men was an average of 0.984; the ratio for women was 0.994. Other studies have found similar hair-splitting differences (Manning’s study found an average ratio of 0.98 for men and 1.0 for women). Some studies have gone so far as to link ratios to sexual preference. While many do, indeed, agree that the ratio variance is a marker for prenatal male hormone exposure, the notion of romantic partner choice is a bit of a stretch, to say the least.
Other skeptics report that the gender difference in ratios is completely inaccurate. A 2017 study found the complete opposite results in gender variance of finger length ratio. The researchers in this group noted that men’s hand sizes are larger than female’s, with associated lengthening of the fourth digit more so than the second. When accounting for hand size, this group found that the 2D:4D ratio was actually larger in men than women.
We’ve got to hand it to these researchers, so assiduously studying these two digits for the past 150+ years. Some have produced powerful data implicating this ratio variance based on gender as a sign of future choice of mates; while others have completely discredited the ratio variance altogether, claiming that when it comes to hands, size does, indeed, matter.
