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Survival of the sickest - calling Dr Moonbear

Posted Nov2-10 at 04:10 PM by Evo
Evo Child bought this when it first came out and she enjoyed it. I'm just starting it.

It's interesting and very easy to read. Basically it tries to explain why some heritable serious diseases today such as diabetes and hemochromatosis may have resulted from a genetic edge the diseases might have given our ancestors.

Dr Moalem has doctorates in neurogenetics, evolutionary medicine, and human physiology.

Has anyone read this book, and have thoughts on it, from a medical perspective?
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  1. Old Comment
    Moonbear's Avatar
    I've never read it, but from the brief bit you posted here, it sounds consistent with what we've taught for many years. The diseases don't really give the edge, but those with a mild case or heterozygous for the alleles that cause it might have an advantage against other conditions. For example, someone with sickle cell anemia will be very sick, but someone heterozygous for it has a better resistance against the malaria parasite.

    There are a lot of medical conditions today that are side effects of a society where a lot of excess is available. Adaptations that might help one survive in times of famine are detrimental in times of excessive availability of foods.

    And then there are things that have more to do with us living longer. People die of things now that they just never lived long enough to have in generations past. The genetics may have always been there, but it didn't matter because nobody lived long enough to know they'd experience it.
    Posted Nov3-10 at 06:57 PM by Moonbear Moonbear is offline
  2. Old Comment
    Evo's Avatar
    Thanks MB!
    Posted Nov3-10 at 08:29 PM by Evo Evo is offline
  3. Old Comment
    The most interesting inheritable disease that gives an evolutionary edge might be favism. People with favism genetically lack a certain enzyme, and as a consequence, when they eat fava beans they get horribly sick, and can even die.

    One might think that this condition would be present mainly in regions where fava beans don't grow. For example, fava beans grow in Africa but not Sweden, so it would seem that if Swedes lacked the enzyme it would be no big deal--Africans would have evolved to have the enzyme, but Swedes would not need it, and could evolutionarily lose the ability to produce it.

    But the situation is quite the opposite! It is precisely in the regions where the beam grows that populations have a genetic predisposition to getting sick or killed by it.

    What is happening is that the bean seriously damages blood cells in suspeptible people in such as way as to make it hard for the malaria parasite to grow in them. The bean is native to regions where malaria is rampant, and the people with the suseptibility live in those regions. Indeed the time the beans "ripen" coincides with the malaria season. So favism provides chemotherapy (with severe side effects) opportunity against malaria.

    In a sense it is like the evolution of sickle cell anemia, but more complex and more interesting. Indeed because malaria has killed so many people there is a lot of selection pressure to counter it, even if countering it has negative effects. There are many genetic diseases besides sickle cell and favism that evolverd to resist malaria.

    Another set of interesting genetic diseases are ones specific to Ashkenazi (Central and Eastern European ) Jews. In those regions the Church historically restricted Jews to certain jobs, jobs which turned uot to require more inteligence than typical jobs. So there was selection pressure for those people to be intelligent. Indeed, it is the case that Ashkenazi Jews score much higher on IQ tests than Sephardic Jews. Some of the genetic diseases specific to Ashkenazi Jews are diseases due to two atypical genes, but it is thought that carriers of only one atypical gene are genetically smarter.
    Posted Jul26-12 at 07:41 AM by ApplePion ApplePion is offline