Ayres and her colleagues had infected each of the animals with the pathogenic bacterium Citrobacter rodentium, and within a few days, some of the mice began losing weight. Their colons became severely inflamed, and the animals died not long after. But other mice that were also exposed to the bacterium looked perfectly healthy. All the mice were genetically identical. They were fed the same food, kept in the same kinds of cages, and had no notable differences in the composition of their microbiomes. “Yet half the animals died, and the other half survived,” exactly what she was aiming for, Ayres tells The Scientist.
Scientists typically assumed that susceptible mice had more-severe infections—that random events drove up the number of pathogenic bacteria and this caused them to die—while surviving animals got lucky and managed to keep pathogen numbers low. But when Ayres tested her mice, levels of bacteria in the gut and other tissues were the same in both groups.Fortunately these mice didn't die in vain. The genome doesn't entirely dictate how an organism turns out, because there are many other factors determining which genes will actually be expressed. The treatment, though apparently quite simple, had more subtle effects than fortifying the mice against attack or killing off the bacteria directly. Rather it seems to have modified the bacteria so that they didn't cause the mice any problems.
Compared with mice that died from the infection, the mice that survived expressed lots of genes linked with metabolizing iron. This indicated to Ayres that iron might help the animals cope with the infection, so she and her team decided to treat mice that were on the verge of dying from the C. rodentium infection with an iron supplement. The animals recovered. Sequencing the genomes of C. rodentium in the control and iron-fortified mice revealed that the bacterium in the mice fed iron had accumulated mutations that tamped down expression of multiple genes for proteins in a virulence pathway, disabling its ability to cause disease. The bacteria, found in the colon, were, in essence, “just part of the [mice’s] microbiome now,” Ayres says.
Fighting infections doesn’t have to be all-out war. Instead of trying to obliterate pathogens that have invaded the body, she proposes, organisms may give them what they want and ultimately push them to evolve into something benign, lessening the damage done by the pathogen and the immune system. This phenomenon known as disease tolerance, is something that the body can do naturally by tapping into different physiological systems, such as metabolism, to prevent illness.If you want more details on disease itself, you should probably skip to the article now. But you might be wondering what all this has to do with steam engines. Well, personally I can't say I'm interested in diseases per se - I'm much more interested in how ideas spread through and influence societies. How policies and social structures encourage and suppress the flow of different ideas, and how we can try and determine which ideas are likely to be harmful and which will be beneficial, is essential to anyone trying to make the world a better place. And we know that any system dependent on transmission, be it diseases or ideas or wildfires, shares certain characteristics that be subject to network analysis.
In one of the Science of Discworld books, the authors note how the invention of the steam engine caused absolutely bugger all to happen. That is, Heron of Alexandria invented a spinning orb propelled by two steam jets. This was sometime in the first century A.D., and though it was recorded, it doesn't seem to have been anything other than an intriguing toy. There's a whole book on Ancient Inventions which is littered with similar examples : prototypes which look like they had enormous potential that was barely exploited, often in cases where the full implications now seem obvious.
The SoD authors expressed this concept as "steam engine time". If the wider society isn't ready for steam engines, then they may get invented sporadically but they'll never do very much. But if it is, then there can be multiple simultaneous inventions of the same technology, and even if there aren't, they can still spread rapidly through the network. So there's a state where the network can tolerate - even welcome - steam engines but not properly exploit them : using them as executive toys instead of improving mining techniques or transportation. In some societies, an idea can spread rapidly and have massive transformative effects; in others it might spread rapidly but not actually do anything, while in others it might be greeted with such universal hostility that it dies a swift death.
Of course there are limits to how far the disease toleration analogy holds in other situations. We certainly don't have to give in to hatred and giving extremists what they want is usually fabulously unsuccessful in integrating them. But we can, perhaps, give them what they need : a sense of social belonging, thereby rendering their craving for hostility impotent and unnecessary. We may tolerate people but not their ideas.
EDIT June 2020 : I feel the need to emphasise that this view does allow for fighting the systems and structures that engender despicable ideas. It should not mean passive toleration and acceptance of hatred, though this trap is all to easy to fall into (see below). And in extremis, is is absolutely necessary to fight the people as well as their ideas, but one should always target their supporting structures first.
And this goes the other way, of course. There's no particular reason to think that some ideas aren't still going the way of Heron's steam engine, apparently mere baubles but actually with revolutionary potential for those with sufficient vision. I'm reminded of this fascinating example of an answer on Quora, which indicates that the prospect of political revolution is critically dependent on the age distribution in society. There are sufficient problems in many Western societies, I think, that it's easy to imagine them degenerating from something more extreme than mere political chaos and into actual chaos, were the context but a little different. We are, in a sense, disease tolerant, but not necessarily in a good way. There are all kinds of social ills that spread and we do very little to stop them.
So disease toleration makes for a very interesting analogy to societies. Sometimes, letting an idea or belief spread but rendering it impotent could be an important way to parry the blow rather than fighting force with force. But at other times it could be a dangerous approach indeed, letting things fester until a slight change in circumstances causes a literal and lethal explosive transformation.
EDIT June 2020 : When I originally wrote this, I didn't really have racism in mind. Recents events would seem to indicate that it's applicable. Another, hitherto unrelated concept I've outline elsewhere on this blog is the idea of instead of trying to outright break the system, bad actors can try and pervert it into something half-broken enough that they get what they want, but no-one is angry enough to start a revolution - everyone just persists in using the equivalent of a half-broken toaster that's just too much trouble to fix. So it is, perhaps, with racism. As a society we've adapted to become disease tolerant by making ourselves into a broken toaster. We have made progress - real, demonstrable progress. Lynchings and slave ships are a thing of the past. But we haven't fully confronted the root issue. Large swathes of certain western nations have been placated but not convinced; their most egregious outrages have been stamped out but the underlying beliefs have been tolerated. As long as they don't cause physical harm, we've said, it's okay to let them hold their appalling views. Too difficult by far to genuinely win them round. That, it is obvious, was a mistake.