So I made some graphs:
Take your pick. They’re the same graph, except the top graph has the homicide rate on a log scale and the bottom on a linear scale, because Honduras’s homicide rate is kind of off the charts.
I couldn’t fit all of the labels onto the graphs, but since most of the countries group by region, you can still figure out roughly where most of them go. The lower left hand corner, low fertility and low homicide, is filled with dots from East Asia and Western Europe. The central-middle-bottom section, of moderate birthrates and below-average homicide rates, has the Muslim countries. The far right–high fertility and medium violence–is mostly African. (Note that Angola and Gambia’s labels have been footnoted at the bottom of the graph.) And the upper left–high violence but moderate fertility–is Latin America. (The high homicide rates are one of the reasons I oppose unfettered Latin American immigration.)
While there is a positive relationship between violence and fertility, this is clearly not the whole story. Just eyeballing the log graph, it looks like a curved line would fit the data better than a straight line, but that’d require polynomial or quadratic regressions and we don’t really need to get into that much detail.
Rather, I suspect that just considering cleanliness explains the graphs: cleaner people are more easily disgusted by other people, and so have fewer children than their aggression levels would predict.
I haven’t found great data on overall “cleanliness” or “disgust rates,” but it appears that Latin Americans are some of the world’s cleanest people:
Brazilians shower nearly 12 times a week, and Mexicans wash their hair more than anyone else.
By contrast, the French and Russians are positively disgusting. (I’m giving India and China a pass here due to limited running water in their countries.)
Here’s another graph, showing similar numbers:
My personal experience with East Asians (Japanese, Taiwanese, etc.,) also suggests that they are cleaner overall than Americans. These countries appear to have been hit with a double-whammy–very clean and low aggression–driving down the interest in sex so far that 60% of girls aged 16-19 claim to be uninterested in sex or even despise it, and even 40-50% of married people haven’t had sex in the past month. They’ve even got a phrase for it, “sex disgust syndrome.”
I don’t find Japanese fertility rates concerning, just because Japan really does need fewer people and the sex-inclined Japanese will quickly replace the non-sex inclined ones, so the issue will work itself out naturally. (And at any rate, I am not really in any position to go telling the Japanese what to do with their own society.)
In our own society, though, I am concerned that decreased monogamy (more “hooking up” via apps like Tinder and Grindr, etc.) is leading to more, not less female concern about male sexual aggression, with all sorts of unfortunate side effects.