If a male animal is sure that the female animal will not reproduce with it, wouldn't it be mathematically optimal for the male to kill the female? (To ensure that no alleles of the "overreact-to-rejection" gene in other males can make use of the female as a reproductive resource)

I might be missing something very obvious here, but I can't seem to see why a gene for "kill-rejecting-potential-mate" wouldn't spread through the gene-pool.

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    $\begingroup$ I think you are missing many possible explanations. For example, females fight back - combat is risky and would be just as likely to prevent success with future potential mates. Additionally, in many species females are on average stronger or larger than males. It also seems to me that reducing the number of potential mates, even after a rejection, is a poor strategy. While a male is busy battling with the rejecting females, the other males are busy mating with all the others. I also don't know what you mean by "overreact-to-rejection" gene... $\endgroup$
    – Bryan Krause
    Jan 27, 2017 at 20:43
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    $\begingroup$ Evolution isn't just about an individual passing its genes on, it's about a population surviving and adapting through time. Limiting your numbers does not appear a good survival strategy on the population level. You are possibly eliminating alleles that are, or would be in the future, of selective advantage. $\endgroup$
    – bpedit
    Jan 27, 2017 at 21:25
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    $\begingroup$ Why do you think all females don't kill males they reject? $\endgroup$
    – swbarnes2
    Jan 27, 2017 at 23:21
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    $\begingroup$ Combat is risk. Rejecting female may kill rejected male.. thereby removing gene for male who over react to rejection. Females may move in groups, so injuring one female member may result in all females in herd to reject said male. Combat take time. While rejected male is spending time killing rejecting female. Other males are mating with non rejecting females. Males do produce daughters. Murderous rejected male, may produce murderous rejecting daughters. $\endgroup$
    – JayCkat
    Jan 28, 2017 at 3:03
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    $\begingroup$ I asked moderators to delete this question, but: 1: Everyone seem to assume that I am misogynist. I'm not. In fact, I am glad to see the "outrage" against apparent misogyny 2: @swbarnes2: because male animals often give very little contribution to reproduction. 3: @ bpedit: a gene that result in the death of a whole population would still spread through the gene pool, even if only in the local gene pool before the latter's destruction. $\endgroup$
    – user289661
    Jan 28, 2017 at 5:20

2 Answers 2


The simple answer is most animals females can fight back. Its similar to the reason male to male fighting often evolves to become more and more ritualized. Fighting is risky, and the closer in size and capabilities the fighters are, the riskier it becomes. Behavior that tends to get you injured for little to no benefit tend not to get passed on. and there is little to no benefit in killing females for a male. Plus a female who is alive can change her mind later, so there is a direct benefit to the male for not harming her.

Now there are animals where a female will be bullied into mating to the point of risking injury or death. Those animals are very rare and have high dimorphism, they have males that are MUCH larger and more dangerous than the females, to the point the female is incapable of being a significant threat to the male. It is most common in animals that express harem polygyny. It also tends to carry the risk of inbreeding.

One horrifying example is hamadryas baboons. Males maintain a harem and threaten any female that even strays too far from the male. They even bite disobedient females.


There's natural selection for males that do what ever they can to stop a female mate they already have from having an affair because if she has an affair, she might produce an offspring that's not his own so they can't get as much food to rear as many of his own offspring. Although killing her makes her unable to have an affair, it's not selected for because she can't produce a kid that is his own either if she's killed. If she deserts him in addition to rejecting him, there's no evolutionary advantage in him killing her because she won't stop him from finding another mate that will produce a kid with him. It would however be an evolutionary advantage for a male to reduce his options and do something to make it so that he will be unable to not kill his mate if she rejects him. Females who did not reject males that reduced their options in that way would be selected for and then in response to that change, males that reduce their options in that way would be selected for. If after that, a mutant male that could make it look like they reduced their options when they didn't arose, it would outcompete the males who actually reduced their options and then females who rejected a male would stop being selected against and maybe it some cases be selected for.

  • $\begingroup$ You need to reread the question more carefully. It is about killing non-receptive females not killing promiscuous ones. $\endgroup$
    – John
    May 21, 2017 at 4:22

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