It is said that the diversity of certain genes evolves in human history. See:
Li H, et al. (2011) Diversification of the ADH1B gene during expansion of modern humans. Ann Hum Genet, 75(4):497-507.
My question is: what's the advantage of a higher diversity? Actually, what I am curious about is: what's the disadvantage if the diversity of certain genes, e.g. the genes on Y chromosome, recedes?
Thanks in advance.
Divesrsity happens because of mutation. In general, higher mutation rate, higher diversity. Then, evolutionary forces shape this random diversity (selection, small population size, non-random mating...). Higher diversity gives populations more opportunities to adapt to an ever changing environment (in general). And also more mutations that can be deletereous too, but if these are recesive that is less of a problem. Higher diversity in teh HLA systems for instance can give you resistanace to a wider range of microbes. Reduced diversity, i.e. higher homozigosity can bring together recesive deletereous alleles, and cause disease and/or reduced fitness, in general. It can also make the individual more apt for a given environment, but the environment always changes (in evolutionary terms).
Dear Prof. Alonso,
Thank you very much for your earnest help!
Your answer is from a general perspective. However, to tell the truth, what I especially concern is the specific genes on Y chromosome, i.e. those genes that are transferred only from father to son. Could the general law summarized by your answer also fit those specific genes?
Ning
Well, as the Y chromosome is non-recombining (most of it), strong selection on any single locus could drive homogeneity in the population not just on that gene but on the whole chromosome. Also if there are few males contributing most of the descendants to the next generation. Diversity can be observed if there is some population structure. Not sure if that is what you are after...
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