EEB214H1 Lecture 21: Human Evolution

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Ecology & Evolutionary Biology
Jennifer Carpenter

EEB214 Lecture 21 Pathogens have many of the same evolutionary patterns we’ve talked about before If there is heterogeneity in the host it will select for: sex • when the environment varies, sex is selected for because sex helps make new gene environments • snail example: variation with how much infection • these bacteria has to deal with different genotype • organisms that can have sex will have it at higher rate so there is sex for variation • in a population that is mixed heterogeneous we expect diseases to evolve • but similar population can select for increase virulence • If there is a competition within a host it will select for o whichever one that is more effective in exploiting the niche is going to spread o resources in the host are limited o e.g., HIV [affects white blood cells] o but only so many white blood cells so if someone’s infected with 2 strains and one grows faster, it can use up that white blood cells o selection makes it more efficient with the resources they have • If they make more virus particles, they’re more likely to spread and more likely to breathe in the more common one • If there are closely related pathogen strains living together o kin selection o if kin selection is acting and these guys are living in a host with another relative, they won’t use up the host because they want to increase their fitness [grow together] o e.g., Malaria in mice • Hygiene hypothesis states that lack of exposure to pathogens has caused our immune systems to become out of balance, causing autoimmune diseases o we are involve to be sick, now we aren’t which cause parasites • Type I diabetes is caused by destruction of insulin producing cells by the immune system o pancreas being attacked by own body o places where there are other infectious disease, less likely to have type I diabetes • If your immune system gets lower, there’s other things that could infect you • Guys with higher immune activity will do better • When immune system gets bored it will start attacking things o happening because we evolve where we always had tapeworms o we have evolve where our genome expected to have tape worm lowering our immune system but now we don’t have it anymore so the immune system attacks our own body o hence is why people suggest that being too clean is affecting our immune system • Multiple sclerosis is characterized by damage to nerve tissue by the immune system o over 4.5 years patients infected with worms did not get worse while uninfected patients did
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