When mothers discover that twins are coming, the trousseau is often planned with the same gifts and even the same clothes for the children.
However, despite having similar characteristics, a new study published in the academic journal Proceedings of the National Academy of Sciences suggests that differences will be exposed over time.
The Northwestern University and Norwegian School of Economics researchers, who carried out the study, concluded that when the twins are a girl and a boy, the differences cause disadvantages for the female side.
And they range from fertility to socio-economic success among siblings.
But calm down, we’ll clarify further in the sequence.
What does the study say?
The researchers began the research using data from 13,800 births of girl-girl and girl-boy twins in Norway between 1967 and 1978, which were followed for 30 years.
The research was based on the hypothesis that girls exposed to testosterone in the womb, due to training with their brother, would have behavioral differences throughout their lives.
To compare the results, the researchers also analyzed women who, despite being twins of a brother, grew up alone, in order to verify how female development happened in different situations.
From the result, it was seen that women who grew up in the same womb as their brother are 15% less likely to graduate from high school and 4% less likely to finish college.
In addition, the researchers also noted that a boy’s female siblings had their fertility rates approximately 6% lower and were still almost 12% less likely to marry.
But all of this has a reason, according to the research, and is called testosterone – male sex hormone.
According to the researchers, these differences in female behavior may be due to exposure to the hormone of the opposite sex still in the mother’s uterus, which occurs through amyotrophic fluid or the mother’s blood.
But beware, the interpretation of this study requires caution, according to its own authors, the results may vary from society to society, being only one of the factors related to behavior.
That is, an observation of how much biology can be related to the future.
The study cited in the news covers a wide range of interpretations, but it can be important for analyzing how hormones interfere with the development of babies of different sexes.