September 14, 2009
In another comment to bring about important discussions on the flu Leonardo asked the following:
I was taking a look at the dates of pandemics: don’t you think these re-arrangements are a little bit connected to agriculture industrialization? Mainly to pigs and poultry farming? Packs full of antibiotics and vaccines? Isn’t it a favorable condition for such new lines of viruses? As far as this aspect is concerned, I guess this pandemic had already been a foreseen reality.
Well, that flu is surely a foreseen reality. Several articles have already discussed that topic. But I am going to let this great text by Reinaldo Lopes, journalist of Folha de São Paulo, originally published at the excellent blog Chapéu, Chicote e Carbono 14, explain it.
It is difficult to think about anything else than the porcine apocalypse this week (mainly when you are working as a journalist in real time. *Sigh*). So, we’d better make use of hysteria (?) in favor of a very important archaeological lesson: how has pigs and other animals taming transformed human societies health? In many cases, it has been transformed into a worse condition – much worse.
Summarizing and even simplifying it, it is almost certain that our species only faces quick development and potentially lethal infectious diseases because it learned how to create other animals in large scale. Flu (of course!), smallpox, whooping cough, measles, cholera, diphtheria, typhus, tuberculosis – before the development of antibiotics and modern medicine in general, we can imagine how much such list of diseases used to kill people. We can say that all these diseases started their “careers” as zoonoses, starting from the genetic proximity to the pathogens that are responsible for them, with viruses or microorganisms carried by domestic animals.
That thesis is one of the prominent elements from the already classical book “ Guns, Germs and Steel” by the American biographer Jared Diamond, from the University of California in Los Angeles – the origin of this post’s title. If we take a look at the process that transformed wild hogs (like the nice animal on the above picture) into domestic pigs we can realize that the epidemiologic dynamics turned upside down because of taming.
First of all, it is hard to compare human and animal population densities before taming events and after taming events. It is true that large mammals such as horses, wild hogs, wild ovines and bovines used to live in groups before becoming farm creatures, but many animals could rarely be confined in such small spaces like humans determined for them.
Of course there was a positive feedback between the domestic animal population and the human population. The amount of animal protein (meat and milk), fuel (feces), fertilizers (feces again), raw material (bones) and clothes (furs) available for large animals raisers is exponentially higher than the amount that could be acquired by the best hunter-collector. Join agriculture to all this and you will have, of course, the possibility of feeding much more people at the same space. Luckily, those exceeding people, thanks to animals, too, can become even more mobile and can move and colonize new lands riding on their horses, oxen, donkeys and buffalos.
Stop and think for a moment how anti-natural this entire situation has been (under the point of view of 6 million years of human evolution) during the ten last millenniums. The chance for close contact with large mammals or even with flocks of birds of the hunters-collectors had been minimal. The guy could thank all the gods if he could slaughter a bison a month. But nowadays you have a lot of people and a lot of animals piled up on the same ground – people dealing with dung, meat, blood, fat and who knows what else that comes from cows, pigs and goats. (The expression “who knows what else” does not have merely a dramatic effect. In Papua New Guinea, women from some tribes’ breastfeed orphan piglets. You see, they breastfeed piglets).
This inedited scenery not only facilitated disease transmission between humans and animals but also made epidemic infectious diseases become self sustainable for the first time. If you are a hunter-collector and are sorry for being infected by a murder pathogen from, let’s say, monkeys, you can be comforted if you are aware that a tribe with more than 50 people will die altogether, or become immune to it very quickly. And probably the sickness will stay right there because those poor people rarely have contact with other groups.
Everything changes completely when we have dense populations of animal raisers and agriculturists inter-linked by trading routes and constant extra-tribal interaction. Nowadays even murder pathogens may benefit from the population critical mass, spread to one or more whole continents and cause too much damage, a fact that was very unlikely to happen in the pre-taming period.
Winners and losers
Diamond extracts an interesting conclusion from all this thinking. (You can check the part of the documentary adaptation based on his book in the video below, which deals with this theme). When European invaders stepped on the Americas, Polynesia and Australia for the first time, the native inhabitants from those places were the ones who died, decimated by smallpox, flu, measles and other Euro-Asian scourges. There is not any sickness coming from those places that reached Europeans.
Well, none of these peoples has tamed animals on a large scale, with the exception of the lhamas tamed by the Incas (that are the only large* tamed mammals in the Americas). Diamond points out that with a smaller population density, the key is the lack of domestic animals. The Europeans inherited a whole lot of micro-organisms transmitted by animals, which killed many people in Eurasia that conquerors ended up by getting immune to them – what didn’t happen to the native inhabitants.
We can’t deny that the conclusion we come to from all this is quite gloomy. Modern hygiene measures and continuous monitoring may help. However, if we take history as our guide, extensive animal raising and the contact between human beings and animals are likely to scare us in the future, when talking about epidemics.
* As a commentator of the original text pointed out, Andean peoples also tamed guinea pigs. Besides that, almost all American tribes had dogs, and so did Polynesian tribes. However, in scale, nothing compares to the variety of mammals tamed in Eurasia.