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According to this study from 1970, cats are about 50% male and 50% female. Furthermore, there appear to be about 100 male pedigree cats born for every 92 female cats.

I couldn't find any info about sex ratios for cats that aren't adapted to live closely with humans. My understanding is that female cats occasionally live in colonies and work together to guard each other and their kittens. Female cats who do not live in colonies still hunt for themselves and their own offspring and protect their offspring.

Male cats...impregnate female cats?

It would take very few male cats to keep the species going. It seems like male cats don't do anything else beneficial to the species besides donate cat sperm to the females who take it from there.

I am wondering why, from an evolutionary perspective, so many male cats would continue to be born. Is this purely for genetic diversity purposes?

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Don't forget that while species evolve, it is individuals that are acted on by selection. Individuals that are successful cause more of their genetic material to be present in the next generation.

Your question is addressed by Fisher's principle.

For an example, imagine you do have a scenario like you describe, where there are fewer males and more females. Let's say, 90 females and 10 males. In the next generation of 100 cats, each female is responsible for on average 100/90 ~= 1.1 offspring per female cat. However, each male cat is responsible for on average 100/10 = 10 offspring per male cat.

Now, imagine some female cats produce 50:50 males:females, and other female cats produce all females. The latter group will have 1.1 x 1.1 ~= 1.2 grandchildren; the former will have (1.1 x 1.1)/2 + (1.1 x 10)/2 = 6.1 grandchildren. In a world where males are rare, it pays to be a female that produces male children.

These are some extreme examples, but in general you'll always have a pressure towards balanced sexes as long as both sexes are required to produce a child.

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    $\begingroup$ I remember figuring this out in SimLife many many years go. You can start out by setting the organism to have a skewed ratio, but over time, they evolve to go to 50:50 $\endgroup$
    – swbarnes2
    Apr 27 at 22:34
  • $\begingroup$ Thanks for writing such a concise and clear answer! It seems so obvious now $\endgroup$
    – ribs2spare
    Apr 28 at 18:57

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