Will the length of fingers tell us how big the brain is? Shocking research related to pregnancy hormones

The evolution of the human brain has long been thought to be linked to larger brain size. Now a new research suggests that high amounts of estrogen (a female hormone) in the mother’s womb before the child is born may have played an important role in this and the surprising thing is that an easy sign of this is hidden in the length of our fingers. Scientists compare the length of the index finger and ring finger. This is called 2D:4D ratio. This ratio tells how much estrogen and how much testosterone (male hormone) the baby received in the womb in the first three months.

• If there is more estrogen and less testosterone in the womb, the index finger becomes longer than the ring finger. In such a situation the 2D:4D ratio is higher (larger).
• If testosterone is high, the ring finger is longer and the ratio is lower.

Study on 225 newborn children

This ratio remains almost the same throughout life even after birth, hence it becomes a kind of permanent signal. Professor John Manning of Swansea University (UK) has been doing research on this topic for many years. He, along with some scientists from Istanbul University, conducted a study on 225 newborn babies. Of these, there were 100 boys and 125 girls. They measured the proportions of the children’s fingers and also measured their head circumference.

What were the results?

• A clear relationship was seen in boys: boys who had a higher 2D:4D ratio, meaning they had more estrogen in the womb. The circumference of his head was also big.
• No such significant relation was seen in girls.

What does the head of a newborn baby say?

Big circumference of the head means big brain and is associated with intelligence. Therefore this discovery is very important for human development. Professor Manning says that along with the increase in brain size in humans, some changes have also taken place in the body. This is called ‘Estrogenized Ape Hypothesis’. That means estrogen helped in making the brain bigger. But an interesting thing is that excess estrogen can also have some disadvantages. In men, a higher 2D:4D ratio has been found to be associated with a higher risk of diseases such as heart disease, low sperm count and schizophrenia.

burden on men’s health

Perhaps the evolution of larger brains made humans very smart, but also placed some burden on men’s health and longevity. This means that the price of our getting a bigger brain may have to be paid to some extent by men’s health. Even in Professor Manning’s old research, this finger ratio has been found to be related to many interesting things like habit of drinking alcohol, recovery from Covid, fitness of athletes etc.