Sneezing. What is it good for?
And how pathogens are the OG hackers.
Of the various feelings that I’ve discussed so far, the feeling that you’re about to sneeze is perhaps the most obvious in terms of what it’s motivating.
That fact does not, however, mean that the need to sneeze isn’t interesting.
Ok, first, let’s start with what sneezing is and what the urge to sneeze is measuring.
On Nostrils
Sneezing is pushing high pressure air from the lungs through the nostrils. The primary function of this is cleaning. We use the same idea for cleaning electronics such as computer keyboards, shooting compressed air through a tube to get rid of dust and crumbs.
Now, humans don’t need to breathe through their nostrils because they have an alternative—the mouth—but there is value in breathing through the nose. Nostrils are useful for keeping things that don’t belong in the lungs out. This list includes foreign particles such as dust and smoke as discussed in the context of Challenges and Insults, toxic chemicals and, of course, pathogens.
Certain cells in the nostrils detect the presence of irritants—these cells are measuring the presence of bits that don’t belong. Think of these cells as having a kind of a keyhole and anything that comes along and fits in the hole—binds to the cell, as biologists like to say —tells the cell that something it’s designed to detect is, fact, there. The cells then send this information along via the trigeminal nerve. Anything that binds to these sensors will affect this measurement and contribute to the accompanying feeling of having to sneeze. Pepper, for example, contains Piperine, which binds to these receptors. In turn, the trigeminal nerve activates the medulla oblongata, a part of the brain, and that leads to the urge—the motivation—to sneeze.
By squeezing air from the lungs through the nose at high pressure, stuff that doesn’t belong in the nostrils that might block breathing or damage the lungs is expelled. Mission accomplished.
Now, we also have to discuss mucus. The immune system is continuously identifying (again, with a lock-and-key system) foreign entities in the body—bacteria, viruses, dust, etc.—and collecting it in batches for disposal. In the same way that you accumulate trash in your kitchen garbage can and then take it out at the end of the week, the body collects the trash in mucus, expelling it as needed.
Now, when your body is under attack by pathogens—viruses and bacteria, especially—the mucus trash fills up faster because your body is packing all those cells into mucus, sending them out to the curb. Too much mucus makes it hard to breathe, which is why sneezing is frequently a symptom of certain kinds of infections. Once the mucus in your nostril is ready to go, achoo!
That might seem like it’s the end of the story, and a very short post.
But wait, there’s more!
The Angler Fish
Like so many systems, this one can be hacked.
Simple systems that measure and motivate are, at their heart, conditionals. IF this THEN that. Going back to the post on awe—one of my favorites, which I encourage you to go and read because it’s our least viewed post—the idea was that IF you detect something that is extraordinary, THEN you direct your gaze at it to gather more information. (And open your mouth, and raise your eyebrows, to signal to others that they should as well.) To put it very abstractly, measure and motivate systems are like this:
IF [conditions are met] THEN [do this thing]
Now, the tricky bit is the conditions. What if something is able to imitate the conditions?
One of my favorite examples is the angler fish. Say you are a fish and your brain is designed to measure the extent to which some stimulus you’re getting from the world is good to eat. If you’re swimming around and there’s little things here and there, then for each one your nervous system is measuring how likely it is that you can and should eat it—checking the size and maybe some other features, such as the texture and how it moves. If it fits the bill, you are motivated to eat it. You can think of this as a reflex or an instinct. Here is how a fish brain works:
IF [small, wriggly thing before me] THEN [eat it]
Therein lies the problem. These conditional rules are part of the “environment” of other organisms. That is, the process of evolution by natural selection can act to shape adaptations in other organisms because of this environmental feature.
So along comes the angler fish. The angler fish has a long structure coming off of its head, looping up and around to the front of its mouth. At the end of this structure—let’s call it a fishing pole—is something that fits the motivational system of other fish. When other fish see this structure—it appears small and wriggly—they are motivated to try to eat it.
This is good for the angler fish because the thing that is not food is, in fact, a lure. By luring the hungry fish near its mouth, it gets an easy meal, gulping the unsuspecting fish who was simply motivated to eat the morsel.
And so it goes.
A Complete Aside: Measuring, Motivating, and Capitalism
Here is the way capitalism works.
Firms create goods and services that fit into humans’ measure and motivate systems. For example, they produce food, which our systems measure as being nutritious, causing us to be motivated to eat them.
Firms also create goods and services that mimic whatever it was that the system evolved to detect. So, firms produce molecules that your mouth tells you contain usable calories—that’s the sweetness—but, in fact, it does not, or has very little. And so we have Diet Coke, a massive branch of the greater Coke empire.
Firms prosper when they produce things people want to consume better than rivals do.
Some of the things they produce are pretty close to what our systems were evolved to consume, such as actual, real food. And some of these products are good at motivating us to consume them but, at the same time, don’t affect our satiety system—the way we know that we are still hungry—in the same way that real food does. Tricksy!
Similarly, AI girlfriends and boyfriends who are attractive, attentive, and devoted are being measured by your evolved system to evaluate possible mates. Changing technology has allowed firms to create, often at very low marginal costs, stimuli that, just like the angler fish, fit into the relevant measurement system.1
This argument applies across the sorts of things that motivate humans, from food to social approval to gossip to sex to comfort to status… Firms are competing to motivate you to consume the goods and services they create. The ones that can produce those goods and services efficiently prosper. All driven by your evolved systems to measure things that are fitness-good for you.
And that’s how capitalism works.2
And Back to Sneezing
The lesson of the angler fish is that when you see organisms doing whatever they were motivated to do, there are (at least) two possibilities that you have to consider:
1. The organism’s system is working as designed, for the benefit of the organism. Huzzah.
2. There is some other organism manipulating the motivational system, producing something that mimics whatever is being measured.3 Boo.
This is very relevant to sneezing. Let’s suppose that you are a pathogen. You’re exploiting your host, which is great for you, but if you don’t get your DNA (or RNA) into another host, then you’re an evolutionary dead end. Now, the environment offers various routes to the next host. For example, some species are pretty social, so one thing you can do if you’re a parasite is take advantage of proximity by flying, hopping, or crawling from one host to the next. Similarly, because organisms have to dispose of waste products, if, by some fluke, you can get your eggs into poop—and ride that poop into another organism—you can potentially pass your genes on to the next host.
Another route is, if you can swing it, to ride a burst of high-pressure air from a nose. The trick here would be to provide whatever it is that is being measured to make the host motivated to sneeze you out. In this way, your descendants can ride the mucus, spittle, and other gross bits that get expelled during a sneeze. So, for example, if you are a pathogen, evolution might favor genes that cause you to target the host’s respiratory system, causing the generation of mucus, stimulating coughing and sneezing.
From this we see that there are two possibilities when you are sneezing. The first is that your system is working just as designed, expelling something unwanted. The second is that, just as in the angler fish case, your system is being manipulated by a pathogen, which is using your sneezing to get to the next host. It’s not a coincidence that the symptoms of various viruses are runny nose, sneezing, and coughing. These effects are the pathogens at work, using your body’s defense systems to get to the next host through the expelled, eh, stuff. Bordetella Pertussis, a bacterium, causes coughing, whooping its way to the next victim.
Now, not all pathogens will be designed to go this sort of route. If you are a vector-borne pathogen, such as malaria, you don’t want to be sneezed out into the world. You want to circulate in the host’s blood stream, hoping the next mosquito will suck you up and take you to the next host. (This is why some vector-borne pathogens cause torpor; they are designed to make the host an easy target for the next mosquito by stopping all that inconvenient moving around and defending itself.)
Similar arguments apply to other escape routes from the body. Do you communicate from one host to another by air? Take the sneeze or cough train. Are you instead designed to get into the water and move into a new host that way? Then you should expect to be designed to motivate excreting fluids from the body, about which, because it’s gross, I’ll say as little as possible.
Conclusion
Having a bunch of systems that measure and motivate is useful. Each one gets a job done, as we’ve seen.
However, because each of these systems is essentially a conditional—if such and such a thing has been measured, then do such and such in response—each one is open to exploitation. If others can mimic whatever it is that’s being measured, then they can activate our motivational system.
My sense is that humans have an appetite for opportunities to pay a small cost to gain a big benefit. Who doesn’t like hunting for buried treasure? Somewhere along the line, someone figured out that while we like making these bets, we’re… not so great at the math. Thus was born lotteries, casinos, and various games of chance, manipulating our treasure-hunting appetite to benefit the house which, in the long run, always wins.
So, when it comes to your motivations…. Caveat emptor.
REFERENCES
Akerlof, G. A., & Shiller, R. J. (2010). Animal spirits: How human psychology drives the economy, and why it matters for global capitalism. Princeton university press.
Dawkins, R., & Krebs, J. R. (1979). Arms races between and within species. Proceedings of the Royal Society of London. Series B. Biological Sciences, 205(1161), 489-511.
Nesse, R. M., & Williams, G. C. (1996). Why we get sick: The new science of Darwinian medicine. Vintage.
Akerlof and Shiller put this very well in Animal Spirits: “But the bounty of capitalism has at least one downside. It does not automatically produce what people really need; it produces what they think they need, and are willing to pay for. If they are willing to pay for real medicine, it will produce real medicine. But if they are also willing to pay for snake oil, it will produce snake oil.”
I’m simplifying. For example, commodities such as oil don’t fit this model. Oil is an input to products that humans do want to consume. So this is really just an approximation.
In the scholarly literature, see the work of Krebs & Dawkins, for example. Citation at the end of this post.