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> I have a pet (non-scientific) theory/query. Wouldn't such prolonged & sustained periods of female foeticide eventually cause the human body to mutate...and st

> I have a pet (non-scientific) theory/query. Wouldn't such prolonged & sustained periods of female foeticide eventually cause the human body to mutate...and stop giving birth to the female sex entirely? It's the opposite, actually. It is evolutionarily favorable to give birth to the sex that is less numerous at sexual maturity. If female babies started dying, for whatever reason, the chance the average baby is female would gradually increase until the ratio of sexually mature females to males balanced out. Incidentally, this is presumably why there are slightly more males born than females [1] - males tend to die more frequently than females during childhood. ___ 1. https://en.wikipedia.org/wiki/Human_sex_ratio https://en.wikipedia.org/wiki/Human_sex_ratio > In humans, the natural ratio between males and females at birth is slightly biased towards the male sex, being estimated to be about 1.05[2] or 1.06[3] males/per female born.

claudiawerner 7y ago
>If female babies started dying, for whatever reason, the chance the average baby is female would gradually increase until the ratio of sexually mature females to males balanced out. Perhaps I'm missing something, but how does the human body have internal knowledge of the current gender ratio in society such that it will attempt to fix the ratio to balance?
- nordsieck 7y ago
  > Perhaps I'm missing something, but how does the human body have internal knowledge of the current gender ratio in society such that it will attempt to fix the ratio to balance? It doesn't. This process happens strictly through natural selection. If average female fertility is F, the number of sexually mature females is f and the number of sexually mature males is m, then the average male fertility is F * f / m (each child is conceived by exactly one male and one female). This means that the less numerous sex has a higher fertility. It is not true that each child is equally likely to be male or female. Some parents are more predisposed to have male children and some parents are more predisposed to have female children. The parents predisposed to have more reproductively successful children will have their genes flourish - pushing the sex balance of new babies slightly in the corrective direction.

claudiawerner 7y ago

>If female babies started dying, for whatever reason, the chance the average baby is female would gradually increase until the ratio of sexually mature females to males balanced out. Perhaps I'm missing something, but how does the human body have internal knowledge of the current gender ratio in society such that it will attempt to fix the ratio to balance?

nordsieck 7y ago
> Perhaps I'm missing something, but how does the human body have internal knowledge of the current gender ratio in society such that it will attempt to fix the ratio to balance? It doesn't. This process happens strictly through natural selection. If average female fertility is F, the number of sexually mature females is f and the number of sexually mature males is m, then the average male fertility is F * f / m (each child is conceived by exactly one male and one female). This means that the less numerous sex has a higher fertility. It is not true that each child is equally likely to be male or female. Some parents are more predisposed to have male children and some parents are more predisposed to have female children. The parents predisposed to have more reproductively successful children will have their genes flourish - pushing the sex balance of new babies slightly in the corrective direction.