Because you are changing the rate of survival often, here is a simple computation.
This is a very rough approximation, but it gives an idea. A few assumption: With a high rate of death at birth, a large pressure will be put on women to have as much babies as they can. That's terrible, but let assume that they are force to give birth until they die. Raising babies will be the work of men. Of course, with such harsh conditions, women are protected and cared by men, so the only moment a woman can die is during birth. Assume no problem of sterility, and with high rate of death at birth, menopause is not an issue. We also ignore twins.
Then, consider a rate of survival at birth of $r$. That is, if $N$ women give birth, $rN$ of them will survive, and have to bear a baby again. On these $rN$, $r^2N$ will have a second baby; $r^3N$ lucky women will have a third baby and so on..
This means that the $N$ women will give birth to $N(1+r+r^2+\dots)=N\frac{1}{1-r}$ babies (geometric series). Half of them, that is $\frac{N}{2}\frac{1}{1-r}$, are girls. If you want a strict renewal of generations, you need $\frac{N}{2}\frac{1}{1-r}=N$, which means $r=\frac{1}{2}$, hence a rate of survival of $50\%$.
With same conditions, a smaller rate of survival will result in a population decreasing more or less slowly. A higher rate of survival means a growing population, or people can stop treating women like animals.
1No humanity, soon. How long ago this supposedly started? – Mołot – 2017-03-20T08:51:56.987
@Molot I'm asking this question as in what if it was like this from the very start, like it has always been human nature. But exploring the possibility of this randomly happening one day is interesting as well, if you or anyone wants to explore that. – Noble – 2017-03-20T08:52:57.303
2
I see that you changed your question quite drastically from 75% to 25%. If you continue this you may invalidate existing answers, which is something we don't like. We have a Sandbox on Meta where you can test questions before releasing them onto the main site and get feedback on style, on-topic/off-topic, grammar, flaws in your premise, ... Might be a good idea to give it a try next time. Currently it's okay with your edits, but please don't lower it any further. You can always ask follow-up questions
– Sec SE - clear Monica's name – 2017-03-20T09:17:49.6731
Do not change questions in a way that invalidates already posted answers. See this: https://meta.stackexchange.com/q/43478/225745 - If you have to, then post a follow-up question with changed premise.
– Mołot – 2017-03-20T09:19:15.103there would be less old women, not sure what the evolutionary advantage would be. – Jodrell – 2017-03-20T09:32:20.640
Your preposition is highly implausible. Such high childbirth mortality results in an incredibly high evolutionary advantage for those women who don't die during childbirth because they can have more offspring and nurture it after birth. Within a few tens of generations you'll either have no people left to give birth or they will have a far lower childbirth mortality. – David Foerster – 2017-03-20T10:12:15.737
1This seems to be too broad. – JDługosz – 2017-03-20T10:13:16.353
1The open ended unguided “what if” or “what does thaf do to society” is too broad for a question here. You can discuss on [meta] or [chat] to get advice and and ideas in editing it, and note that the post can be reopened again after discussion. – JDługosz – 2017-03-20T10:21:55.013