Hormones have a direct influence on finger length

Prenatal hormone levels determine the finger length of humans

06/09/2011

The finger length is determined by the prenatal hormone level. Researchers have been speculating for some years that there is a direct relationship between pre-birth hormone levels and the length of the fingers, as both factors are determined by the same gene sequence. Now, US scientists at the University of Florida at Gainesville have clearly demonstrated scientifically that finger length is affected by prenatal hormone levels.

Estrogen and testosterone determine the finger length
Like Martin Cohn and Zhengui Zheng from the University of Florida in the journal „Proceedings of the National Academy of Sciences“ (PNAS) report that the different length ratio between ring and index finger in men and women is demonstrably due to the proportion of female and male hormones during embryonic development. Depending on the estrogen or testosterone content, this leads either to a longer ring finger than index fingers in men or a longer index than ring finger in women, the US researchers explained. In a comprehensive study, scientists at the University of Florida have studied the impact of prenatal hormone levels on the „finger length“ examined in mice. The results allow conclusions about the interaction of finger length and hormone levels in humans, as the mice have a human-like finger length ratio, explained the US researchers.

In their investigations, the US scientists discovered in the budding fingers of the mouse embryos a particularly high density of receptors for the sex hormones testosterone and estrogen. When blocking the testosterone receptors, the mice developed a typical female finger length ratio, report Martin Cohn and Zhengui Zheng. The same effect has been shown with additional administration of estrogen. On the other hand, when testosterone was added, the mouse embryos had the typical male finger length ratio of a longer ring finger than an index finger, according to the US researchers. This was the first clear evidence that the prenatal hormone level determines the finger length, explained the experts of the University of Florida.

Prenatal hormone levels are crucial for individual characteristics?
Although there was no scientific evidence to date for the relationship between prenatal hormone levels and finger length, previous studies already used finger length as an indicator of hormone levels. Based on this indicator, the studies then linked hormone levels to certain characteristics such as behavior, technical or social interest, sexual orientation, and masculine gender. The individual disease risk for autism, breast cancer, depression and heart disease has also been linked to prenatal hormone levels in the investigation. Even sexual attraction and success later in life have been associated with finger length or prenatal hormone levels. However, most of these investigations had clear deficiencies and found correspondingly little consideration in the medical community. One of the criticisms was always the extrapolation of the prenatal hormone level based on the finger length. However, since the current study of US researchers now provides a clear evidence of the effects of prenatal hormone levels on the finger length, the previous criticism seems unjustified, at least on this point. (Fp)

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