![]() For one thing, some r esearch suggests that mothers with elevated testosterone levels influence the testosterone levels of their daughters (but there appears to be no such influence with maternal testosterone on boys). Some research has also found that the first-born child, whether male or female, is exposed to more estrogen prenatally, for reasons we don’t yet understand.Įnvironmental factors are in play as well. Genetics certainly play a role, both of the mother and the fetus. What causes these differences in the levels of sex hormones in the womb? Scientists aren’t yet sure, though they have some hunches. What Causes Differences in the Levels of Sex Hormones in the Womb? The higher your 2D:4D ratio, the less testosterone or more estrogen you were exposed to as a fetus. So the lower your 2D:4D digit ratio is, the more testosterone or less estrogen you were exposed to in the womb. Mice with higher testosterone concentrations or low estrogen levels had more male-like digit ratios (low 2D:4D ratio), while mice with higher estrogen levels or low testosterone levels had higher, more feminine digit ratios (high 2D:4D ratios).Ĭohn and Zheng posit that what’s true for mice is true for humans as well: prenatal exposure to a mixture of testosterone and estrogen is what determines 2D:4D ratios. What they discovered is that it’s not just the amount of fetal testosterone that determines digit ratio, but rather the balance between testosterone and estrogen. Consequently, animal studies can provide insight into why these general differences exist.ĭevelopmental biologists Martin Cohn and Zhengui Zheng conducted experiments on fetal mice in which they modified the amounts of testosterone they were exposed to in utero. While prenatal testing and studies are difficult-to-impossible to ethically conduct on human fetuses, the general difference between 2D:4D ratios in human males and females also exists between the sexes of other animals. It wasn’t until 2011, however, that scientists were able to directly show that prenatal exposure to testosterone determines the 2D:4D ratio. Other researchers came to similar conclusions using corollary evidence. In 1998, further strides were made when psychologist John Manning of the University of Liverpool (now at Swansea University) published a paper in which he hypothesized that 2D:4D ratios are determined by prenatal exposure to testosterone. Glenn Wilson of King’s College was one of the first to hypothesize that 2D:4D finger ratio was determined by sex hormone exposure in the womb. While scientists during the mid-20 th century were able to statistically establish this general difference between men’s and women’s 2D:4D ratios, it wasn’t until the 1980s that researchers began speculating as to why this sex difference exists and how 2D:4D ratios may correlate with different gender traits. The Connection Between 2D:4D Ratio and Prenatal Hormones 83, and some folks have really high digit ratios, like 1.06. Some men have really low digit ratios, like. A longer index finger compared to your ring finger is considered a “high 2D:4D ratio.”ĭigit ratios lie on a spectrum. If your index finger is 3.1 inches long and your ring finger is 2.9 inches long, your 2D:4D ratio would be 1.06 (3.1/2.9 = 1.06). A longer ring finger compared to your index finger is considered a “low 2D:4D ratio.” So if your index finger is 2.9 inches long and your ring finger is 3.1 inches long, you have a 2D:4D ratio of. They’ve called this difference in length between the index finger and ring finger the “2D:4D ratio.”ĢD stands for “second digit” - that’s your index finger, and 4D means “fourth digit” - your ring finger. With women, it tends to be the reverse: their index fingers are usually longer. Scientists have long noticed that men’s ring fingers are generally longer than their index fingers. Prenatal Testosterone, Androgen Receptors, and 2D:4D Finger Ratios How strong is this correlation and what exactly does it foretell? I’ve dived deep into all the available research to sort myth from fact, and present this comprehensive look at what digit ratio really means for your masculinity. Well, while it might sound like hokey palm reading, researchers are finding that the ratio between the length of your ring and index fingers may in fact correlate to your prenatal exposure to T, and have a significant influence on your body, brain, and behavior well into adulthood. Then you were exposed to lower levels of T as a fetus. Is your index finger longer than your ring finger? If so, you were likely exposed to higher levels of testosterone while you were in your mother’s womb. Is your ring finger longer than your index finger? Stop what you’re doing and look at your hands.
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