That's already been dramatically undermined by current population trends. The birthrate is falling everywhere, including in sub-Saharan Africa. Although Africa's population is on track to keep expanding, this expansion looks big mainly in comparison with Europe, which is in the throes of demographic collapse from which it is not likely to recover --- ever.
Although Sub-Saharan Africa's fertility rate is high now, it's dropping as you can see from the World Bank chart, below. You can have fun extending the African lines down, if you want: this chart makes it look like they'd Ethiopia and Congo's lines will intersect Iran's in my lifetime, and Iran's decline has been precipitous:
Trends indicate that sub-Saharan Africa will decline to merely replacement rate by 2100. By that time, in Europe is still in existence as Europe (inhabited by indigenous Europeans) is anybody's guess.
I don't think it's wise to impose Europe's demographic geno-suicide on everybody. Here's an interesting recent article on how fertility has been declining across the globe.
that chart certainly has pretty colors, but constant tribal war, greedy, corrupt and ineffective governments, lack of infrastructure, lack of potable water, inability for food self-sufficiency, disease, ignorance, apathy, lethargy and much more will guarantee that population growth curve never happens in Africa ...
An exponential population growth curve doesn’t hold together unless nutrition, medical intervention, and especially sanitation improve accordingly. More population pressure results in expansion of contact with wildlife harboring microbes. Many animal species are carriers of hemorrhagic fevers as an example.
It’s reasonable to take the position that there are disease vectors we have had no encounters with as yet. An increase in population density results in an out-sized likelihood of finding something nasty which results in a pandemic outbreak, one which will check growth of a population.
