Evolution News - How a Human Malarial Parasite Evolved From a Chimpanzee Parasite

Chimpanzees in Kibale National Park, Uganda.

Credit: Yannick Tylle via Getty Images

Malaria parasite puzzle solved as ape origin found | The University of Edinburgh

the An open access paper published in Nature Communications yesterday, illustrates how, contrary to creationist claims, the Theory of Evolution is not only alive and kicking, but is the fundamental theory underpinning most of biomedical research.

The paper, by an international team of scientists led by Dr. Lindsey J. Plenderleith of the Institute of Evolutionary Biology and Centre for Immunity, Infection and Evolution, University of Edinburgh, Edinburgh, Scotland, UK and including colleagues from the Department of Medicine, University of Pennsylvania, Philadelphia, PA, USA and the Recherche Translationnelle Appliquée au VIH et aux Maladies Infectieuses, Institut de Recherche pour le Développement, University of Montpellier, Montpellier, France, and others, solves the 100-year-old mystery of the origins of a species of the malaria-causing parasite, Plasmodium malariae which is distinct from the commoner, P. falciparum and P. vivax which normally cause the disease in humans. P. malariae is morphologically identical to a species found in the other African apes and was once thought to be the same species.

Among the six parasites that cause malaria in humans, P. malariae is one of the least well understood. Our findings could provide vital clues on how it became able to infect people, as well as helping scientists gauge if further jumps of ape parasites into humans are likely.

Dr. Lindsey J. Plenderleith, lead author
Institute of Evolutionary Biology and Centre for Immunity, Infection and Evolution,
University of Edinburgh, Edinburgh, Scotland, UK

It is unusual for a Plasmodium parasite to infect two or more different species as they tend to be highly specific in their choice of host species. Until recently however, the techniques for extracting and analysing DNA were not available to verify this one way or the other. Using modern techniques, the Edinburgh team, in cooperation with colleagues in Pennsylvania have now shown that there are, in fact, three different Plasmodium species; one, P. malariae, which infects humans and two which infect chimpanzees, gorillas and bonobos in Central and West Africa. The previously unknown species is only distantly related to P. malariae, but the second is much more closely related to it.

A comparison of the genomes of the two closely related species shows that the human-infecting species, P. malariae, is much less genetically diverse than the one which infects the other African apes and shows evidence of having gone through an evolutionary bottleneck where the population was reduced to just a few individuals, hence most genetic diversity was lost. The most parsimonious explanation is that P. malariae originated as a parasite on chimpanzees, gorillas and bonobos then crossed the species barrier into humans when a small number found themselves in a human host.

This illustrates a basic principle of evolution - the 'founder effect', where a small founding population is not a representative sample of the parent population and starts off with different allele frequencies to the parent population, so meeting the criteria for evolution - a change in allele frequency over time. A similar mechanism is believed to have been behind the evolution of the more common P. falciparum.

In this case, the difficulty of crossing and recrossing the species barrier created a physical barrier which kept the newly-emerged species isolated in the human hosts, so allowing it to evolve without further genetic introgression.

Until this work, one of the candidates for the parent species of P. malariae was P. brasilianum which infects new world monkeys. However, the team have shown that the most likely origin of this species was P. malariae which crossed from humans into new world monkeys, and not vice versa.

The team's open access paper is published in Nature Communications:

Abstract
The human parasite Plasmodium malariae has relatives infecting African apes (Plasmodium rodhaini) and New World monkeys (Plasmodium brasilianum), but its origins remain unknown. Using a novel approach to characterise P. malariae-related sequences in wild and captive African apes, we found that this group comprises three distinct lineages, one of which represents a previously unknown, highly divergent species infecting chimpanzees, bonobos and gorillas across central Africa. A second ape-derived lineage is much more closely related to the third, human-infective lineage P. malariae, but exhibits little evidence of genetic exchange with it, and so likely represents a separate species. Moreover, the levels and nature of genetic polymorphisms in P. malariae indicate that it resulted from the zoonotic transmission of an African ape parasite, reminiscent of the origin of P. falciparum. In contrast, P. brasilianum falls within the radiation of human P. malariae, and thus reflects a recent anthroponosis.

Plenderleith, Lindsey J.; Liu, Weimin; Li, Yingying; Loy, Dorothy E.; Mollison, Ewan; Connell, Jesse; Ayouba, Ahidjo; Esteban, Amandine; Peeters, Martine; Sanz, Crickette M.; Morgan, David B.; Wolfe, Nathan D.; Ulrich, Markus; Sachse, Andreas; Calvignac-Spencer, Sébastien; Leendertz, Fabian H.; Shaw, George M.; Hahn, Beatrice H.; Sharp, Paul M.
Zoonotic origin of the human malaria parasite Plasmodium malariae from African apes
Nature Communications 13, 1868 (2022).; DOI: 10.1038/s41467-022-29306-4

Copyright: © 2022 The authors. Published by Springer Nature Ltd.
Open access
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

If they were honest and faced the facts, findings like this present a major problem for science-denying creationists. Not only does it show, contrary to their increasingly forlorn claims, that the Theory of Evolution is alive and well, but it provides a framework for understanding a great deal of biomedical science, which would not make sense without it. Then there are examples such as this, where even those creationists who have conceded that evolution works but only within their poorly-defined taxons, have to face the fact that any intelligence behind this evolutionary change must have consciously and intentionally been producing yet another parasite to make the life of its victims more miserable.

And yet, to maintain their opposition to Darwinian Evolution, creationists prefer to present the 'intelligent [sic] designer' of these nasty little parasites as some sort of hate-filled divine malevolence, completely at odds with the supposedly omni-benevolent god of the Bible and Qur'an. One can't but help wonder what, if it were real, any divine creator of these things would think of its advocates who prefer it to be presented as a pestilential, sadistic monster, who hates its creation, rather than concede that science is right about how the biodiversity on Earth arose and changes over time, and how humans are related to it and part of it.

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