General Musing

I was watching one of these science programs on National Geographic about the connection of the relation between testosterone exposure in the womb and finger length.

The foetus makes most of the testosterone itself. In males, it comes from the testes and adrenal glands; in females from the adrenals alone. Only a small amount will comes from the mother. In women this results in the ring finger and index finger being about the same length. However in men the index finger will usually be the shorter of the two digits.

“It has been known for some time that there is a direct correlation between finger lengths and the amount of the male sex hormone testosterone that a baby is exposed to in the womb.
In women, the two fingers are usually almost equal in length, as measured from the crease nearest the palm to the fingertip. A longer index finger is associated with higher levels of oestrogen and luteinising hormone, both of which are known to play critical roles in egg production. In men, the ring finger tends to be much longer than the index.”¹

Elevated or high levels of testosterone in the womb have been linked to several brain-related phenomena, including aggression, fertility, left-handedness, autism, dyslexia and controversially male and female sexual orientation.

Aggression
The shorter the index finger of a man is compared to the ring finger, the more boisterous he is. This doesn’t true for verbal aggression or hostile behaviours.² “No such connection was found in women.“

However a different study found a correlation for women exposed to higher levels of testosterone in the womb, they had a more ‘male’ pattern of finger length. And they displayed more frustrated behaviour when answering challenging telephone calls than other women, to the point of smashing down the phone after the conversation.

Fertility
A long ring finger in men and symmetrical hands are an indication of fertility. Men with mirror-image hands are more likely to have a high sperm count than those with two asymmetrical hands. Twelve of the least fertile men in the study, who were producing almost no sperm, had the least symmetrical hands. Women are more likely to be fertile if they have a longer index finger.

Experimentation on mice found that the gene Hox affects digits as well as the ovaries and testes, although a similar genetic link in humans has yet to be found.³

Autism
Autistic children had extremely long ring fingers compared with their index fingers, whereas children with Asperger’s also had abnormal index-to-ring finger ratios, though less so than full-blown autistics. It’s possible that families with autistic children may have a genetic predisposed for the production of high levels of testosterone during early development, as even the unaffected siblings and parents of the autistic children had ratios that differed significantly from the normal controls.⁴

Sexual Orientation
The length of the fingers could also be an indication of sexual orientation, although the study is controversial.⁵ In both lesbian women and homosexual males with several older brothers (I don’t do the tests) have a greater difference in length between their ring and index fingers than their straight counterparts.⁶

Other
Excess testosterone has also been implicated in the origins of migraine, stuttering, schizophrenia and depression.⁷

1. Finger length ‘key to aggression’
2. Finger Length Predicts Aggression in Men
3. Fingers point to fertility levels
4. Finger Length Ratios
5. A finger on sexuality
6. Finger-length ratios and sexual orientation
7. Hidden significance of a man’s ring finger

• Finger length heart attack clue
• Finger length helps predict SAT exam results, study shows
• Digit Ratio (Wikipedia)

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