Sex Ratios: What if the global ratio of males and females changed?

The ratio of men and women in the world is remarkably similar with males being only slightly more common than females. In some countries the ratio is slightly higher than others but it doesn’t change much and hasn’t over the course of recorded history. You can read more about the distribution of chromosomes and the reason why our gender ratio stays generally constant. It is really fascinating but I didn’t feel like rewriting it. I wanted more to consider what would happen if this golden ratio were to change. What if we the new Covid vaccine caused only female embryos to implant in vaccinated women? What if some new pesticide caused male embryos to not live to term? What if we suddenly lived in a world with 25% men and 75% women? How does society change when the ratio of men and women shifts?

In 2020, 101.69 Males were born for every 100 females. Men are born at a slightly higher rate than women and men have a shorter life expectancy which helps to minimize that gap especially among the older side of the population. Cities in Europe have noted a “man drought” with ratios of 45M:55F. With females being the limiting factor in reproduction due to the gestation period for pregnancy, it seems that a significantly higher ratio of females to males would be the evolutionally expectation. One male can reproduce with multiple females to boost reproduction rates.

It seems that a higher ratio of either gender would throw our societal expectation of monogamy out the window. Would it become a class based society where the more scarce gender has a heightened social status? Would you see the societal relationship norm become polygamy or polyandry? Would we see a rise in homosexuality rates among the more populous gender? Of course my scenario is considering only biological sex and not gender. Perhaps we would see a greater rate of transgender people. A nongenetic gender drift, if you will.

We would probably see societal problems and attempts in government enforcement. Consider the impact of China’s son preference as it related to their “one child” policy. As a result, there is a large male surplus in China, South Korea and several other Asian countries.

I’ll bet we would see new scientific initiatives to find medications to alter the birthrate or allow parents to select the gender of their offspring? I’m sure we would see an increase in sexism? If males were suddenly more valuable, perhaps we would see them relegated to household tasks instead of playing with guns and sending them off to fight our wars. I can only assume that females were seen as more valuable which is why society has tried to keep us safer. I think back to the movie The Titanic, as the ship sinks and the crew yells women and children first. Clearly there is a higher value on the lives of women and children, perhaps this is because women are the caregivers for children and their survival may be linked to that of the children.

Thankfully, we don’t have to worry about a long term biological sex deficit due in part to Fisher’s principle. The basis of this principle is the following:

1. Suppose male births are less common than female.
2. A newborn male then has better mating prospects than a newborn female, and therefore can expect to have more offspring.
3. Therefore parents genetically disposed to produce males tend to have more than average numbers of grandchildren born to them.
4. Therefore the genes for male-producing tendencies spread, and male births become more common.
5. As the 1:1 sex ratio is approached, the advantage associated with producing males dies away.
6. The same reasoning holds if females are substituted for males throughout. Therefore 1:1 is the equilibrium ratio.

It sounds like we’ve seen little change to our gender ratio but I’d like to thank you for once again entertaining another random shower thought from your favorite blogger.

What other effects do you think we would see if the sex ratio changed?

What do you think would happen if the transgender rate changed significantly and it suddenly became unfashionable to be either male or female? With if anyone with the means to purchase hormones and pay for gender reassignment decided to do the ol’ swaparoo.

I apologize in advance to my trans readers, this post is probably horribly insensitive. I don’t mean any offense, I’m just throwing random ideas out in the same manner that they exist in my head – the crudest form.