Whenever the topic of Africa's historical population is approached, I always see two methods for determining the population, and two camps. It's odd that the historical community seems split like this, and I wanted to see how the people on this subreddit would weigh in. (This post is copied from the one of PDX forums, yes.)
The first group I've found believes Africa's population didn't exceed 50 million until at least 1500 A.D. They usually justify this by using back-projections from colonial population censuses. When the question of how the population could remain so low emerges, the answer given is that there isn't a suitable climate for mass production of calorie-dense goods.
The other group usually doesn't offer an estimate for the entire continent, but offers high enough estimates for particular regions of Africa, like the Kingdom of Benin, the Malian Empire, the Kingdom of Kongo, or the Kilwa sultanate, that the estimates can't peacefully coexist with those of the first group.
The reason this is a problem is because the second group tends to offer evidence directly from those regions, such as testimony from contemporaries, food production methods, documented village densities, and inferences from side texts. Evidence like this has placed me in the second group, and the wide-reaching explanations of the first just seem simplistic to me.
The fact remains that, not only is the second group split, but it also seems to be somewhat under-spoken when compared to the first group, as you have to do a bit of extra searching to find their answers.
When it comes to the population sizes of historical African cities, there are massive divides on how many people it could've held. Great Zimbabwe and Mbanza Kongo are estimated at having been capable of holding anywhere from 10,000 to 50,000 people, depending on who you ask.
Here's the question: In the years before 1500 A.D, do you believe Africa had a population in excess of 50,000,000 people? Yes or no? Why?
(I want to wait until others have provided their opinions before I bring in the evidence I've gathered.)
Not a question for historians. Even in historical time, its noted that "little is known about even the relatively recent demographic history of Africa, because of the lack of data" [Walters:2016]; nothing gets clearer as you go back farther in time.
We've got very little historical data before 1500 CE. Estimates of sub-Saharan populations prior to a written historical record are the domain of archaeologists, demographers, geneticists, anthropologists-- the historical record is negligible. Many will use the numbers arrived at by Angus Maddison (an economist) they are plausible, but you can't say much more than that for them.
The most comprehensive look at the question that I know if is now some 40 odd years old "African Historical Demography" [Edinburgh:1977 and 1981]
There's a nice review of subsequent work k in
Cordell, Dennis D. “African Historical Demography in the Years since Edinburgh.” History in Africa, vol. 27, 2000, pp. 61–89.
. . . but that only takes you up to 2000. I've looked for a more recent review like this, but I'm not aware of one.
It's a fair guess that it will be the geneticists, demographers, archaeologists and anthropologists who will give us improvements in understanding of African populations-- but historians don't have much to say on the subject. We're not even sure of the size of the Roman population.
So you can pick a plausible number and there's no one who can say "you're wrong" with any great confidence.