Talk:Lizardman/@comment-179.127.113.200-20180719014952/@comment-45.56.46.26-20180721014106

Humans might be considered to have a population of which about half would be female, of that half about half would be in their reproductive years, of that quarter about half might have a child in any given year. These fairly maximally favorable assumptions need to be placed against an average life expectancy which would indicate some attrition each year. If women in the population are spending half their life reproductively active, that means they are often dying before finishing their reproductive years, thus reducing the fraction of the female population that could be fertile in a given year, for instance.

Similarly, if you are keeping old people around till they die naturally of aging, then the proportion of the life-span during which females are fertile also decreases. As mentioned before, having available aspirations that compete with the satisfaction of having children means that fewer of the females capable of having children will have them in any given year. Lowering the death rate would tend to imply both of these.

Anyway, a fairly typical doubling time for a highly fertile human population with a life expectancy of around thirty (many deaths in infancy/childhood would be the typical shape of that death curve, leading to a lower proportion of reproductive years statistically) then the doubling time might be from 8-12 years. If you increase the life expectancy through hygiene, nutrition, etc. so that most people would die of old age, so it is closer to 80, then the fertile span of a typical female's life is proportionally smaller (per individual, not just statistically). Females are also likely to choose to forgo reproduction opportunities to focus on improving their economic situation in various ways, so the children per fertile female per year drops too.

So you could be talking about a doubling rate that is more than 16 years as a result. It's especially significant that Ainz wants to have Lizardmen become SKAdventurers™, meaning a major new alternative to having kids for healthy young adult females. Hopefully he realizes that it would be important for them to retire while they still had any chance of having kids, but still.

While Lizardmen may begin having children earlier in life, having children is pretty hard work. Starting earlier just means that you end up wanting to quit sooner (this affects both male and female libido, though in different ways). So it's not like shorter time to sexual maturity really means a lot in overall population dynamics as long as you have a K-strategist dynamic (i.e. don't just abandon your kids shortly after birth).