In a reasonably large population, this simply just isn't possible by chance. It's possible for a couple to have multiple children and each child be the same sex, but the probability of every couple having children of only or nearly only one sex is simply vanishingly small. The probability of one child being born a male or a female is independent of the sex of the previous child. Since it is essentially a 50% chance of having either sex, you would multiply (1/2)(n) where n would be the number of children in order to determine the probability of having children of all one sex. When speaking of cities or entire cultures, n is a large number that is on the order of thousands or more. This means that the probability is so low that it could be considered impossible on the timescale of human history. Similarly, the probability of having a sex ratio of, say, 1:9 would also be vanishingly small.

Another thing to consider is that the limiting factor when it comes to a population's ability to reproduce is really the number of females rather than males (as long as at least a few males exist). A single male can obviously impregnate many females. So, even if a very low number of females were born in a particular generation, it wouldn't really impact the society's ability to reproduce.

Disclaimer: this explanation is only valid when ignoring cultural impacts on a generation's sex ratio. People have and continue to influence the sex ratio through practices such as infanticide of the non-preferred gender and war. I'm only talking about dumb luck.