Frogs and Snails or Sugar and Spice?
Ever wondered how masculine or feminine you really were? Well it's all in the finger according to evolutionary biologist John Manning.
After measuring the ring finger of thousands of men and women Manning discovered that the levels of testosterone and oestrogen you get in the womb determines the length of your finger. Interestingly, genes which control the development of the fingers also control the development of the testes and ovaries. The amounts of male or female hormones received in the womb determines ring finger length.
Get Your Tape Measures Out
According to Manning "Because the development of the ring finger is under the influence of testosterone males have longer ring fingers relative to their index fingers than women do." The longer the finger, the more testosterone. Conversely men who received low foetal concentrations of testosterone have a shorter fourth to second finger ratio.
A women with a ring finger longer than the index finger is likely to have received an extra squirt of testosterone in utero. Women whose fourth finger is shorter than their second finger would have received higher levels of various female hormones such as oestrogen, prolactin and luteinising hormone. It should be noted that the differences in the two finger ratios are usually quite small.
Researchers first cottoned on to the idea that there might be something in this hand to sex hormone connection through work done back in 1986 on the genes of fruit flies and the discovery of something called the homeobox. This is a DNA sequence found in the genes of many animals and is involved in the regulation of patterns of development, such as head-to-tail organization.
We are still learning about this homeobox gene - but we do know that the homeobox is in every creature where we have gone looking. Each of these living creatures has - and that goes for humans as well.
The bit of the homeobox that controls the manufacture of your hands also controls the manufacture of your genitals. More specifically, the ends of your arms (the hands) and the end of your trunk (the genitals) are controlled by the same bit of DNA. We know (from this study) this is definitely locked in by the age of two.
Dr. Karl Kruzelnicki, ABC Science
So the next time some posturing brute gives you the finger take a look at the digits either side to determine their real machismo levels.
Catalyst Science, ABC
The research was carried out by Dr Manning and his team from the Population Biology Research Group, at the School Of Biological Sciences, University of LiverpooL