Since the 1800s, the levels of testosterone has been steadily rising in males across the world. The increase in male testosterone has increased strength, speed, height, energy, and aggression. The downside is that health and lifespan had been declining. Males are burning out and dying much earlier than normal. By the 2000s, the effects have become the norm around the planet, with males producing thousands of times higher than centuries before. The average life expectancy for men today is now between 35 and 45 years of age.

Women have largely been unaffected by this change. Females also produce increased testosterone, although a much lesser amount than males. With this change happening in the species, it should be logical to expect some increase in female production rates as well, with affects being deeper voices, hair, and other physical changes. And yet, rates have been steady throughout the world.

I need a way to explain why the testosterone increase is occurring in one sex but not the other, despite them producing the same hormone. How would men's metabolism change this much?

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    $\begingroup$ Firstly I think you should make it clear that this is a fictional world not this world. To that end, I've edited the tags accordingly. $\endgroup$ Commented Mar 1, 2020 at 17:54
  • $\begingroup$ @BLT-Bub shouldn't it be obvious that this is a fictional world? $\endgroup$
    – Incognito
    Commented Mar 1, 2020 at 18:19
  • $\begingroup$ To thee and me, no doubt yes. Not everyone here has had a science education, it pays to clarify for readers from all backgrounds. $\endgroup$ Commented Mar 1, 2020 at 18:22
  • $\begingroup$ You might be dead on in your prognostication in your prophetic prophesy postulating the pathetic 'done sex', even though it might have been a slip of the keyboard. $\endgroup$ Commented Mar 1, 2020 at 18:30
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    $\begingroup$ It depends on where the increased testosterone comes from. In humans, testosterone is produced by the testicles (obviously) and by the suprarenal glands. If the increase in testosterone in males comes from the testicles, then females are trivially protected, because they do not have testicles. $\endgroup$
    – AlexP
    Commented Mar 1, 2020 at 19:59

2 Answers 2


You really do not need to speculate, or go deep into quasi-biology, or postulate anything exceptional or revolutionary, or even evolutionarily abnormal. The answer is in the Y chromosome. Females do not have the Y chromosome.

And the Y chromosome is definitely degenerating, because in males there is only one copy, and if there is a defect, there is no 'alternative source' for the genetic material. The Y chromosome turns out to be a particularly useless chromosome, more trouble than it is worth, a failed evolutionary modification.

Testosterone is not the ONLY hormone that causes the changes you are proposing. Testosterone always works in conjunction with other hormones, neurotransmitters and other factors.

The levels of estrogen also mitigate effects of testosterone.

And testosterone is not needed for sperm development.

Because females have dual full X chromosomes (The Y chromosome is something like 80-90% smaller than the X chromosome, it has lost so much genetic material over the eons) Females are known to have less susceptibility to illnesses that genes on the X chromosome protect against, but have been lost from the Y chromosome.

Some species have responded to this by eliminating the Y chromosome completely, such that every offspring has a double-X chromosome. The bottom line truth is, the Y chromosome and testosterone are not absolutely necessary to produce a 'male' sperm capable of reproducing. They are just a result of an evolutionary artifact that coincidentally happen to create the link between male sperm and aggression. There was no absolute evolutionary necessity for the two to be linked. See https://theconversation.com/the-y-chromosome-is-disappearing-so-what-will-happen-to-men-90125 for background.

Here is another really in-depth article covering sex differences in the brain and their effects on male behavior and aggression.


  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – Monty Wild
    Commented Mar 7, 2020 at 17:16

Its a genetic change in the male genitals.

Testosterone isnt exclusively produced by the male genitals, but it is in a larger quantity than in females. So if a genetic change causes the male genitals to produce more then females arent affected because they dont have those genitals to begin with, even though they might still carry the genes for that increased testosteron into their male children.


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