The Genetic Advantages of Females

Written By Ritvik Ranjan

Throughout the developed world, women outlive men, on average, by more than five years! This staggering difference in life expectancy was thought to be due to the more stereotypically reckless lifestyle of men; however, it was recently discovered that women have clear genetic advantages over men. This article from Science ReWired explores why women outlive men by such a large margin and unveils the other genetic advantages the female body provides.

What is the difference in a woman’s body?

The human body is composed of trillions of cells, which are the building blocks of life. Every cell has 23 pairs of chromosomes and 46 total chromosomes (23 from each parent). The 23rd chromosome pair is made up of the sex chromosomes, which are either X or Y. Females will have a pair of X-chromosomes, while every male will have one X and one Y chromosome. Because the mother will pass down an X-chromosome, the father’s sex chromosome determines the gender of the child.

How does an X chromosome differ from a Y chromosome?

An X chromosome is five times larger and carries ten times the number of genes than a Y chromosome. Additionally, Y chromosomes tend to use more genes for male sex determination and development, while X chromosomes’ genes contain more information to create proteins, which are used for a variety of roles around the body. However, a woman does not need two X chromosomes, so one randomly selected X-chromosome is “silenced”, in a process called X-chromosome inactivation. In X-chromosome inactivation, one of a woman’s X-chromosomes are condensed and no longer used in the cell, so that a woman does not have double the expression of genes (so double the necessary proteins).

The old theory

Once it was discovered that men had shorter life expectancies than women, it was believed that women lived longer than men due to the male tendency to engage in “riskier behaviors.” These behaviors included higher rates of smoking, excessive alcohol consumption, and participation in dangerous activities/jobs. Such choices can lead to various health problems and accidents, which contribute to their shorter life expectancy. Additionally, it was presumed that men may be less likely to seek medical care promptly, which can further affect their health outcomes. This theory was proven to be flawed however by a study performed from 1890-1995. German scientists identified the life expectancies among over ten thousand nuns and monks, a remarkably large data set. The nuns and monks had similar lifestyle regardless of their sex, and so were not exposed to the same types of labor and behavioural risk factors, deeming the experiment as an excellent test to see how men and women fared when lifestyle was not a factor. Even in this study, the women outlived men, suggesting that there was a biological reason for this phenomenon.

How does the X-chromosome make a difference?

Now let’s tie all of this together. Within cells, the X-chromosomes are essentially the more important chromosomes regarding cellular functions beyond sex-determination. This means that if the X-chromosome is not functioning properly, then the cell will be greatly affected and unable to perform the required function. Therefore, it is an immense biological advantage to have a backup X-chromosome that can replace the failed one. However, you may remember that the other X-chromosome was silenced in women. So how did the inactivated chromosome become activated? It’s actually quite simple; it’s through a process called X-chromosome reactivation. In this process, the cell reverses the condensing of the X-chromosome, allowing it to be restored to its original form, which typically does not have the mutation. An example of a disease that benefits from this process is Hemophilia, a bleeding disorder. It is X-linked, which means that it is spread through the X-chromosome and is far more common in men because women have the extra X-chromosome to fight it off. There is an uncountable amount of other diseases in which having two X-chromosomes provides a genetical advantage, and women can endure these far more strongly than men.

The discrepancy in life expectancy between men and women is a fascinating genetic puzzle. Contrary to the supposed notion, the X-chromosome silencing and reactivation is the reason for this astonishing difference. However, the genetic intricacies of the additional X-chromosome in women are still unfolding today. Researchers are rapidly uncovering new facets of its potential, shedding light on its role beyond genetic diversity, and unveiling a realm of untapped possibilities that promise to deepen our understanding of the female genetic advantage.

Works Cited

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CBC/Radio Canada. (2020, June 19). Female genetic superiority: When it comes to survival, two X chromosomes beat an X and a y | CBC radio. CBCnews. https://www.cbc.ca/radio/quirks/jun-20-acosmic-iceberg-visitation-female-genetic-superiority-and-more-1.5606487/female-geneticsuperiority-when-it-comes-to-survival-two-x-chromosomes-beat-an-x-and-a-y-1.5617471

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Life expectancy of the World Population. Worldometer. (n.d.). https://www.worldometers.info/demographics/life-expectancy/

Moalem, S. (2021). The better half: On the genetic superiority of women. Penguin Books.

Roseanne F. Zhao, Ph. D. N. M. D. /Ph. D. P. T. P. S. (n.d.). The Y chromosome: Beyond gender determination. Genome.gov. https://www.genome.gov/27557513/the-y-chromosome-beyond-gender-determination#:~:text=The%20X%20and%20Y%20chromosomes,only%20pass%20on%20X%20chromosomes

U.S. National Library of Medicine. (n.d.). X chromosome: Medlineplus genetics. MedlinePlus. https://medlineplus.gov/genetics/chromosome/x/#:~:text=The%20X%20chromosome%20likely%20contains,different%20roles%20in%20the%20body