“The extraordinary variety of human parasites that exist in Africa suggests that Africa was the principal cradle for humankind, for nowhere else did the adjustment between human and nonhuman forms of life achieve anything like the same biological elaboration.
Many of the parasitic worms and protozoa that abound in Africa do not provoke immune reactions.
Opportunities for transfer from one host to another multiply with increased human density…when a critical threshold is surpassed, infection can suddenly develop into runaway hyperinfection. Such epidemic situations seriously interfere with normal activity…
This…can soon reduce a population until the local density sinks safely below the threshold necessary for hyperinfection.
The establishment of human hunters at the top of the food chain…did not…do much to alter these age-old ecological relations. In triumphantly claiming a new niche, humanity did not, therefore, transform the system as a whole.
Until relatively recent times (say five thousand years ago), human communities in Africa played a comparatively modest role amid the abundance of other life forms. Humans were the chief predators, to be sure, but remained relatively rare in the balance of nature.
It is…mainly because sleeping sickness…remains so devastating to human populations that the ungulate herds of the African savanna have survived to the present. Without modern prophylaxis, humans simply cannot live in regions where the tsetse fly abounds…Within the tsetse’s range, something resembling a pre-human ecological balance survives to the present.
In leaving tropical environments behind, our ancestors also escaped many of the parasites and disease organisms to which their predecessors and tropical contemporaries were accustomed.
Humanity’s place within the balance of nature in tropical regions differed fundamentally from what developed in temperate and Arctic climatic zones.
The array…of infections and infestations was vastly diminished from what had thriven in the tropical luxuriance of humanity’s oldest habitat.
Thus humankind’s biological dominion in temperate climes assumed a different order of magnitude from the start.
Humanity was in a situation like rabbits met when introduced into Australia. Lacking both natural predators and natural parasites in the new environment…
Food production permitted a vast and rapid increase in the number of people, and so sustained the rise of cities and civilizations.”
Plagues and Peoples
William H McNeill
Excerpts taken from pages, 19-30 in no exact order so long as I put the main idea out there as succinctly as possible.
This guy is brilliant, but he really needed an editor.