Imagine that you’re at the mall and you see someone you don’t like – maybe an ex or that annoying kid from high school – but the mall is crowded that day and you can easily blend into the crowd and escape. Now imagine that the mall isn’t crowded. This unsavory person sees you and walks over. Because there aren’t a lot of people around for you to hide among, now you have to talk to someone you’d really rather avoid. In the case of infectious diseases, what actually happens is your body becomes the feeding ground of an organism whose numbers have been so long controlled by preventative medicine that they have all but faded from cultural memory.
I’m reading a book right now (Plagues and Peoples by William H. McNeill) that at one point compares the spread of early humans out of Africa to a disease. He has a good argument, saying that the ability of humans to use technology allowed them to mutate, in effect, faster than local wildlife could respond and comparing human expansion to a pandemic. I might have used an invasive species as a metaphor rather than a disease because in this case it wouldn’t really be a metaphor – humans were at the time an invasive species. But in a book about pathogenesis in humans, such a comparison is apt.
So here is the question: to what extent is our history as a species inevitable?