Aspects of Evolution and Ecology of Tsetse Flies and Trypanosomiasis in Prehistoric African Environment

Abstract

Exposure to and invasion by parasitic organisms may play an important part among many other intrinsic factors that guide the evolution of animal forms. Trypanosomes, two species of which cause African sleeping sickness today, are blood parasites of great antiquity. Their presence in Africa at the time of the first stages of human evolution may have been of great consequence, at first acting as a discriminating agent between resistant and non-resistant types of hominids, and later also in shaping migration routes and settlement patterns. As a possible clue as to why man arose in Africa, the author postulates that trypanosomes may have precluded the development of certain ground-dwelling faunas, allowing certain more resistant primates to fill the empty ecological niches. Some of these primates, thus becoming ground-dwellers, became the precursors of the hominid branch. The evolution of T. gambiense and T. rhodestense, the two human parasites, and their development in the tsetse fly, are debated. The epidemiological aspects and patterns of the disease are examined under the changing climatic conditions of the Pleistocene and during later times, when Africa was opened up by Western exploration.