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Science Frontiers ONLINE No. 36: Nov-Dec 1984 |
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Evolution Of Man And Malaria
Malarial parasites are customarily classified according to the species infected and then further subdivided by morphology and biological characteristics. The two assumptions implicit in this classification procedure, which is supposed to mirror actual historical evolution, are:
- Malarial parasites evolved in parallel with their hosts; and
- Morphology is a measure of evolutionary relatedness.
With modern biochemical techniques it is possible to test these assumptions by comparing the DNA structures of the different malarial parasites. P. falcipa rum, the parasite transmitting the most deadly human malaria, turns out to be more closely related to rodent and avian malaria than the other primate malarias. Therefore, assumption #1 above is in correct in this view. Assumption #2 is also wrong because some species of malaria parasites which are very similar morphologically are quite different DNAwise.
(McCutchan, Thomas F., et al; "Evolutionary Relatedness of Plasmodium Species as Determined by the Structure of DNA," Science, 225:808, 1984.)
Comment. The article does not draw attention to still another assumption; namely, that similarities are measures of evolutionary relatedness. If this as sumption isn't correct, evolutionary family trees based on bodily structure, which means most of the family trees in the textbooks, may not truly reflect what really happened in the development of life. Further, if malarial parasites did evolve along with their hosts, hu man evolution seems farther removed from the evolution of the other primates than usually supposed.