Guest post: Diseases like the Black Death change societies

Originally a comment by Claire on Ask Doctor Oz next. (Excuse two guest posts from the same person in one day but if you people will insist on being wantonly informative and clarifying this way it simply can’t be helped.)

Herd immunity. For a pandemic. Fuck.

Herd immunity is a population specific term. Herd immunity is used in humans for very specific reasons. Calculating the vaccination rate required to reduce infections in a population. In a retrospective manner, looking at historical data. Projecting into the future in worse case scenarios and measuring against interventions and their efficacy.

By the time you’re working with populations, they’ve stopped being people and have become mere numbers. Epidemiologists have to remind themselves from time to time that there are people behind the number, but not think about it too often because that way madness lies.

Herd immunity is the worst case scenario in a population that could become immune to the disease over time. This occurs not because people change or the virus changes but because the makeup of the population changes. Most of the people unable to become immune die, those left restrict the virus’ ability to find a human host. Here’s the problem – this virus is zoonotic. It can infect other animals, much in the way that flu does. So achieving extinction is impossible. It can sit there happily mutating in a bird or a mammal of any species – (probably but not exclusively) chickens and pigs, respectively.

Dr Atlas is proposing an attempt to achieve herd immunity through natural selection. Yes, good old fashioned eugenics. Consider the Black Death. That epidemic killed between one and two thirds of the population of Europe. It signaled the end of feudalism and severely limited the genetic pool in people of European ancestry. (We white people are like clones compared with the rest of humanity).

Diseases like the Black Death change societies. I don’t know if Dr Atlas will like the result. Nor will the white supremacists. Battling a disease that can literally almost wipe out a continent’s worth of people is easier the more genetic variation you have. People of African ancestry have the most (it’s the oldest population, older = more time to recombine and mutate DNA). White people have the least. Not because of age exclusively, but because of one epidemic effect 670 years ago. Evolutionarily a blink but in terms of historical impact, it was huge.

Herd immunity assumes the possibility of immunity either natural or through vaccination. If long term immunity cannot be achieved, modern civilization is heading for the biggest transformation since the fall of the Roman empire which plunged European civilization into the Dark Ages or the Great Flood of Gun-Yu which heralded the beginning of dynastic succession in what later became China.

And if long term immunity isn’t possible? We may see the greatest transformation of a civilization you’ve ever seen. A global transformation. The biggest, most beautiful, in history.

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