Transgender Science: Is it All In the Digits? - Digit ration - John T. Manning - Transgender Universe

Today we attempt to get to the bottom of an often discussed theory that claims the size of your ring finger compared to your index finger can determine many prenatal factors during child birth. This theory is otherwise known as the digit ratio theory (the 2D:4D finger ratio). Could the length of your fingers indicate a predisposition to certain diseases, homosexuality and even being transgender? John Manning, a professor in psychology of the University of Central Lancashire and the University of Liverpool, has a book aptly titled Digit Ratio: A Pointer to Fertility, Behavior, and Health where the author delves into this theory.

Could the length of your fingers indicate a predisposition to certain diseases, homosexuality and even being transgender?

Before we go any further let us make sure we are on the same page for this discussion. If you look at your right hand when it is facing down you would count from you thumb (being 1) and move left to your pinky (being 5). So your index finger is 2 and your ring finger is 4. Now that we have it straightened out, let’s proceed.

In a 2011 article from, they lay out the 7 key elements to this hypothesis.

1 – 2D:4D Finger ratio results from the balance between prenatal testosterone & prenatal estrogen;

2 – High 2D:4D finger ratio results from low testosterone concentrations OR high estrogen concentrations;

3 – Low 2D:4D finger ratio results from high testosterone concentrations OR low estrogen concentrations;

4 – The ring finger (4D) has much more hormone receptors than the index finger (2D), therefore the 2D:4D finger ratio is mostly driven by changes in the length of the ring finger (due to prenatal hormone concentrations);

5 – Studies in human & animals indicate that the link between prenatal hormones and 2D:4D finger ratio is generally stronger for the right hand;

6 – 2D:4D Finger ratio varies with sex: males generally have longer fourth digits relative to second digits than females;

7 – 2D:4D Finger ratio varies with ethnicity.




Excellent so what does this mean? Well the theory claims the larger the difference between the length of your index finger and the length of your ring finger the more you were exposed to testosterone during prenatal development. For example in research the professor conducted with patients who had Klinefelter’s syndrome, an intersex condition where men assigned at birth have low testosterone as one of the indicators, their digit ratios were closer to those of cisgender women.

So what does this mean for the transgender community? If you subscribe to this theory someone who is male to female should have closer lengths in their 2d and 4d fingers. Just like cisgender women. It would be the opposite for female to males according to the theory. The rest of his research is based on masculine and feminine traits due to these hormone exposures such as sports acumen and disease factors. This direct binary thinking is not something we subscribe to here at Transgender Universe. As far as hormone exposure in utero explaining homosexuality there is not much science available for us to weigh in. We were able to find one study on self identified lesbians that was done by Rutgers University that found that those who identified more masculine had a bigger difference in the length of the two fingers. Regarding the transgender community we do know prenatal hormone exposure is quickly becoming an accepted theory as to it’s origins but we are waiting on more studies.

So is it true? Well the studies are limited. Some say it is relevant while others feel it is utterly ridiculous as it does not factor in things such as genetics which can also determine the size of your hands. Our view is though this study may show some indications regarding testosterone exposure in the womb it is not enough to determine if someone is transgender or not. We also have so many variations in gender identity that we are not sure how they would relate to this study.

What do you think? Please take our poll below.



  • Leonie

    One of the two times mentioning “female to male” you probably mean “male to female”. (“If you subscribe to this theory… “)

    Apart from that, I find it very difficult to lay my fingers straight. I can easily shift my fingers laterally to “be either male or female” (wow, so symbolic. -.- :D), but I actually wouldn’t know where the middle is.

    • Leonie thanks for the catch on the “Female to Male” error. We straightened it out and we appreciate it! For the exercise you can just look down at your hand. If your ring and index fingers are closer together in length it would mean less testosterone according to this theory. If your index finger is shorter it would mean more testosterone. Anyway what do you think? Urban legend or are they onto something? Also, thank you for commenting! We appreciate your input!

      • Leonie

        Well, indeed my 2D and 4D seem to be pretty much the same length – could be an mtf indication.
        Still it doesn’t seem like it’s a super widely accepted theory, is it? I find a hand reading website to be a rather questionable source. (no matter how scientific the site tries to present itself) The person running the site, a certain Martijn van Mensvoort also does not appear like a scientist of any kind, but rather a hand reading enthusiast who earns his money by writing about the subject.
        On Wikipedia I find tabular listing in the section “Correlation between digit ratio and traits” a little dangerous in terms of interpretation, since it could easily be understood as if these correlations are all causal (men are more/less/better at/… Because of testosterone.), but societal expectations in e.g. gender roles play a huge role. Just recent studies showed that attributions to males and females, like how well you can do maths or navigate, are rather a question of practice than of predetermination. And a matter of one’s own identity. What if I would have known/understood all my life that I’m a girl? I now have a very good sense of orientation… Would I not have it? Or is my sense of orientation an indication that I’m “not really trans”? Do my sense of orientation and my ability to lead groups prove that I’m just autogynophile, but actually a dude? People could draw such conclusions from these charts. at least seems to have done some real science on the digit ratio. I can’t assess the quality of this study and I don’t know the results of peer review, but their abstract does sound compelling:


        Prenatal exposure to androgens has been implicated in transsexualism but the etiology of the condition remains unclear. The ratio of the 2nd to the 4th (2D:4D) digit lengths has been suggested to be negatively correlated to prenatal androgen exposure. We wanted to assess differences in 2D:4D ratio between transsexuals and controls.

        Sixty-three male-to-female transsexuals (MFT), 43 female-to-male transsexuals (FMT), and 65 female and 58 male controls were included in the study. Photocopies of the palms and digits of the hands were taken of all subjects and 2D:4D ratios were measured, according to standard published procedures.

        Comparison between right-handed individuals revealed that the right-hand 2D:4D in MFT is higher than in control males but similar to that observed in control females. In FMT we found no differences in 2D:4D relative to control females. Our findings support a biological etiology of male-to-female transsexualism, implicating decreased prenatal androgen exposure in MFT. We have found no indication of a role of prenatal hormone exposure in female-to-male transsexualism.”

        You know, I’d love to have some proof that I am trans. I am finding so many reasons trying to rationalize my intuitive identity, strengthening and supporting my narrative of growing up and having these and those tendencies and wishes and dreams and all the secret cross dressing and so on… But in the end all the rationalizing drives me crazy and it always comes to the irrational feeling that I just WANT so much to transition. It feels like I BELONG to the girls.
        But experience with how this society works (and I am happy that we are building a fact and science based society rather than one based on beliefs, even though intuition needs to find its own place in there, being the result of complex processes which we do not understand in detail), it seems like I need proof. Some a**hole terf on Facebook slapped my face with “your feelings don’t entitle you to [insert xyz]”. How can I defend myself if I can’t base my being trans on science? How can I then be sure to myself that my inner drive towards finally transitioning isn’t going to just send me into a very unhappy, lonely life of “the weird guy who thought he has to be a woman. HAHAHA”?
        Most difficult choice to ever make. And least understood in the world. But I just freaking want to do it already…

        • Leonie we certainly agree with your assessment on the digit ratio theory. Though it was written by a PHD we certainly wrestled with the choice to label it under “science”. The point was to get the conversation going on the topic of who, what and why we are. Digit ratio certainly does not provide that answer.

          On your second point regarding TERF’s and identity etc., we just want to say that you do not need to prove who you are to anyone. We do understand that some of us need to prove it to ourselves though and we get your point. It is our opinion that maybe we were always what we are and society’s notions forced some of us not to come to terms with it sooner.

          There is some good science out there and your response has given us purpose to explore it in next week’s science article. The whole point of Transgender Universe is to be a resource for all of us and a safe place to discuss these issues. That is why your input is so important to us. You are not alone in what is going through your mind. Most of us go through the very same thing. Hopefully we get to the point where we can do what is good for us and not worry about what others think. This is easier said than done though. We understand that.

          Today we did a profile on Harry Benjamin who was the first to explore the very question you proposed. His book, “The Transsexual Phenomenon”, though now a bit dated, explores some of the questions we often have. It is readily available online. We promise to explore the science of transgender more in the future and help you find the information you need to “arm” yourself. We really appreciate you getting involved as it is the most important piece of what we are trying to do. We look forward to more of you insights. We are always here to help. You can also email us anytime at Know that we are in your corner and thank you for getting involved! – TU

        • Very insightful Leonie. I can agree that the science behind the 2D:4D argument is at best in its infancy and in need of further exploration. Correlations between in utero hormone levels and even chromosome balances can have an effect on development. Exposing the fetus to external “chemicals” or “pharmaceuticals” would alter the heretofore “normal” expectations of fetal growth. Would that skew the numbers in the study groups? Does pre-mature birth alter the development of the baby…? I am excited to read more of this science in the succeeding years.

          When you ask yourself “who am I” and your response aligns to being transgender, that is all the proof you need. Self acceptance is a process. When your time is right, you will know, and your journey that brought you to that moment is your path, be it your need to rely on scientific reasoning or the ethereal guidance of a faith based belief. Following that path to a life of happiness, you will know you made the right decision. When you are on your path, you will be less concerned of what others think, will not let them guide your life’s decisions.

          As Mila cited, there are many resources through TransgenderUniverse. And always reach out to your therapist as much as you need to.

          mir, Irini, peace, amn.


  • Hughspeaks

    In one of the facebook groups I’m a mamber of, we had an informal poll among members on digit ratio, and around half of those who participated had the female ratio. That must be considerably more than the cis male population, and supports the idea that low prenatal androgen levels play a role in MTF transsexuality.

    There’s a whole set of these body markers of low testosterone, which are known collectively as “eunuchoid habitus”, and include things such as:
    * long, slender arms and legs
    * a leg length that’s significantly greater than the height of your upper body (the two should be about equal in men)
    * an armspan 3cm or more greater than your height.
    * sparse or very fine body hair
    * a female “escutcheon” or pubic hair pattern (like an upside down triangle and confined to the pubic region)
    * difficulty building upper body muscle
    * feminine facial features and a generally feminine appearance (soft chubby features rather than hard muscular ones; gracile bone structure etc).
    * gynecomastica
    * other things such as female digit ratio (index finger equal to or longer than ring finger); female carrying angle; absence of acne as a teenager; long, luxuriant eyelashes and comparatively small, high arched feet (in my case anyway!).

    Basically you end up with a body structure that’s more like the female members of your family than the male ones. It’s more noticeable during your teens and 20s, after that, testosterone (even at below normal male levels) will have masculinised your body to the point where you don’t look very different from ordinary men any more. This kind of body structure is an indicator of hypogonadism (chronic below normal male testosterone production), and is something that’s usually associated with intersex conditions. Anecdotally, way more of us MTF and transfeminine people seem to have it than is the case for the cis male population (although I haven’t tracked down any studies where anyone’s systematically evaluated trans people for it). This is another argument for trans actually being a form of intersex, except one in which the main effects have been on the brain rather than the genitals.