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Bantu speaking people moved into central and western Africa

Bantu speaking people moved into central and western Africa...

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Bantu speaking people moved into central and western Africa. A slash and burn agriculture opened up habitat for mosquitoes and along with them came Plasmodium the malarial agent. Consider a large population with the above fitness exposed to malaria for the first time. f(A) ~ 1.0 f(S) and f(C) very low, thus all S and C alleles will be in heterozygous states as AC or SC. Virtually No SS or CC genotypes will be present (the product of two very small numbers). Selection will lead to an increase of the S allele due to its higher fitness as a AS heterozygote. Expect no change in the C allele because heterozygotes have equal or lower fitness than other common genotypes. Can't "pass through" the heterozygote stage. Selection is "short-sighted" cannot "see" the best solution, i.e., the highest fitness
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Unformatted text preview: state where C goes to fixation. How do we get to the "best" condition? Consider the effects of population structure: Bantu people establish local breeding groups of small effective population size. This necessarily will bring on some inbreeding which serves to increase homozygotes and decrease heterozygotes. Some CC genotypes will be produced by the chance effects of inbreeding and now the "best" genotype is present in the population and selection can "see" it so the frequency of the C allele increases, and the population would go to fixation for C. The highest fitness state could not be reached by selection alone; Drift can affect the outcome of selection . This has been conceptualized as an Adaptive landscape:...
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