https://en.wikipedia.org/wiki/List_of_countries_by_population_in_1900
Obviously today Nigeria's population is huge compared to the rest of the nations in Africa, much less the world. I thought it might be a relatively recent phenomenon, but even in the list from Wikipedia Northern and Southern Nigeria have a combined population of 16 million, the next two African regions (Morocco and Egypt) have about 8 million each, and Sudan and Abyssinia having about 4.8 and 4 million respectively. Why such a huge population in that region? Could I just be underestimating the size of Nigeria in comparison to the other regions of the time and countries today?
This question was asked a couple of months ago, here is the link to that thread
As the linked post points out, it's a large area with productive soils and plentiful freshwater resources, to which I'd add long agricultural traditions, going back further than most of sub-Saharan Africa's.
But I'd also be wary of some of wikipedia's populations - Nigeria's 15-16 million in 1900 compares with about 10.2m in Egypt and probably upwards of twice the reported number for Ethiopia (Morocco conversely had nearer 5m than 8m people), so the Nigeria:Egypt ratio was 1.5:1 rather than 2:1, Nigeria:Ethiopia 2:1 or less rather than 4:1.
Just as an indication of how sloppy the data are, the article reports a world total of 1.7 billion whereas its country estimates sum to under 1.55bn: the real total was probably roughly mid-way between.