Comment by jjk166 | Hacker News Reader

Comment by jjk166 | Hacker News Reader

Parent Full thread

I think it makes sense that our microbiome should be able to trigger such a response. If your microbiome is changing, it means that some microbe is gaining numbers it didn't previously have, and your current bodily functions, such as your immune system, aren't stopping it. That doesn't necessarily mean your immune system is compromised, but if it is then it would probably be good not to spend a lot of time around other individuals, especially large groups or strangers. Other reasons for your microbiome to be shifting, like a sudden change in diet or enviroment, could also be indicative of an issue like food shortages or territorial change where it would also be good to minimize your exposure to and reliance on others. Finally, depending on what exactly is gaining a foothold, you could potentially be a threat to your kin if you come around them. Developing a social fear response to certain changes in gut microbiome could thus be quite beneficial for most social creatures.

The problem with Evolutionary Psychology is that it’s easy to construct this sort of “just so” story for pretty much any causal link, and they are not falsifiable.

IMO the simpler hypothesis here is that this isn’t anything adaptive, it’s just another example of how biology is like spaghetti code; changing one chemical signal will affect an essentially random set of downstream systems, some of which can be causally connected to psychology/behavior.

Could also be like climate change, where it correctly describes a broad phenomenon, but cannot be used to identify or classify any individual event. E.g., Wildfires are probably getting worse because of climate change, but it's difficult to say if the Pacific Palisades fire would not have happened in a cooler global climate.

So, is microbiome-mediated social anxiety selected for as an advantageous trait for societies subject to communicable diseases and the travails of nomadism? Maybe. Did YOUR microbiome-mediated social anxiety arise because it was advantageous for your community? Probably impossible to say.

Also, a hole in GP's logic: you would expect protective social anxiety to arise in people whose situation hasn't much changed except that they've encountered people whose has (as with sedentary villagers encountering nomads who may or may not be about to ransack their settlement).

Wildfires are worse in areas where the wrong type of trees were planted as well which is common in logging areas or places cheaply "reforested" that don't do much research on what should be growing there. Wildfires themselves aren't bad per say either as certain trees only grow from fires. Not to say that climate change isn't a factor though, but there are a lot of varibles too.

> you would expect protective social anxiety to arise in people whose situation hasn't much changed except that they've encountered people whose has (as with sedentary villagers encountering nomads who may or may not be about to ransack their settlement).

No, you would not expect that. If rats that self-isolate when their gut micro-biomes change avoid diseases that other rats get afflicted with, then evolution will lead to the mechanism spreading through the rats over time. The rats do not need to know why self-isolating helps, they do not need to even know that self-isolating helps, and they do not need to be in the position where it would help the most.

GP's hypothesis is that diet/environment microbiome changes induce a protective social anxiety. However, a nomadic population - the most likely to exhibit those changes - are successful when exhibiting prosocial or confrontational characteristics, the opposite of social anxiety. Social anxiety is most protective for sedentary groups, who probably should be suspicious of outsiders.

Nothing you said contradicts this, and I'm not sure how to square the circle, even though microbiome-mediated behavior as an explanation for broad, otherwise irrational behavior patterns is attractive.

That isn't a problem because no one speaks of these suppositions in terms of "just so" but in terms of "could be due to." If you want to prove something as just so you have to do a lot more work describing a mechanism of action and that involves reaching into a different toolbox.

> IMO the simpler hypothesis here is that this isn’t anything adaptive, it’s just another example of how biology is like spaghetti code; changing one chemical signal will affect an essentially random set of downstream systems, some of which can be causally connected to psychology/behavior.

That's not a competing hypothesis. Obviously the change to the gut affects other things, some of which happen to impact psychology and behavior.

The question is why does this particular change to gut microbiome have such a similar impact on two different species that diverged many tens of millions of years ago? "It just does" is not a very satisfying answer.

Which would still be natural selection though.

Makes me wonder how many other "maladaptive" responses today actually had adaptive roots in a different context

Beneficial for the group, not the individual, I suppose.

How is it not beneficial for the individual to avoid threats to their health and safety?

I mean the individual who is sick is now sent into a downward spiral of anxiety and frustration instead of evolution helping them (e.g. by making others take care of them, etc.)

Which is to say, maladaptive. Despite all the people wishing evolution worked at the group level, it doesn't. Groups don't have offspring, individuals do, and thus things that are bad for the individual are extinguished regardless of their effect on the group.

If you look closely enough, even individuals aren't the true units of evolution, for the same reason; competing alleles is where the real action is.

When thinking about evolutionary forces, you cannot conflate "positive" outcome with survival and reproduction. An individual might survive and produce offspring via effects that make the individual unhappy in their own life and/or with shortened life.

It's only when an effect causes death or infertility prior to normal reproductive phases that we can really say it has a direct evolutionary pressure. Anything that happens later is always going to be through secondary, social effects on how their condition supports or hinders their offspring from reproducing further generations.

Alleles are shared with kin which gives rise to multilevel selection effects in rare but real scenarios.

Voting me down doesn't change the fact that group selection is a myth. A myth that some people are fervently attached to, but a myth nonetheless. Groups simply don't reproduce at a rate or fidelity to allow evolution at the group level over the time scales in question.

E pur si muove.

Reply on news.ycombinator.com