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Are there any organisms that do not want to reproduce? As humans, there are people who do not want to reproduce with the opposite sex. Do any other organisms replicate this behavior? Also, why does this behavior exist? If the end goal of an organism is to reproduce, why has evolution allowed organisms that do not want to reproduce to exist?

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marked as duplicate by Remi.b, Community Oct 20 '17 at 0:05

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  • $\begingroup$ Are you talking about homosexuality? $\endgroup$ – Remi.b Oct 18 '17 at 18:18
  • $\begingroup$ Hydra dont age and only have sex when food is scarce to leave spawn for next season. they devide. komodo dragons dont need sex to have eggs, whiptail lizards, marbled crabs and many many other animals are asexual: cuteness.com/article/animals-use-asexual-reproduction some 10 pc of rams, male sheep, stick insects, sawfish, snakes ... search for asexual animals. parthogenesis. $\endgroup$ – com.prehensible Oct 19 '17 at 6:56
  • $\begingroup$ @Remi.b — The poster did not mention homosexuality. Have you never encountered heterosexual couples that don't want to have children and are able to fulfill their wishes through contraception. The question is silly in attributiing human emotions to non-human animals, but it is not about homosexuality. $\endgroup$ – David Oct 19 '17 at 8:44
  • $\begingroup$ @David You're right. I'd think however, that the answer remain similar I would guess. It will be hard to talk about 'will of having babies' with heterosexual couples in animals. $\endgroup$ – Remi.b Oct 19 '17 at 16:29
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Animals and especially female animals might not "want" to reproduce when circumstances are bad for babies. Pregnancy and rearing of infants is a big commitment of resources for female mammals. If a female is under stress, or sick she might avoid having sex even though she could get pregnant because evolutionarily that was a winning strategy for her ancestors - committing the physical and nutritional resources to a pregnancy and fetus unlikely to survive current circumstances puts the mother and subsequent pregnancies at risk.

A more extreme example is the Bruce Effect. Pregnant females exposed to the pheromones of a strange new male "decide" not to reproduce - their bodies resorb the fetuses. Presumably this is because the new male is a risk to the fetus and they would do better calling off the doomed project, and possibly having a new litter with the new male if he shows up.

Weirder is the circumstance of parents that kill and sometimes eat their young. That happens in mammals, birds, fish and others. It is hard to see how this sort of thing advances genetic fitness - it seems like a crossed wire or misfire of some sort. Certain animals, however, seem to do it all the time; hamsters come to mind. Maybe stress causes weird behavior? In any case this too would seem like a case of deciding not to reproduce.

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