This is a special post for quick takes by Ben Goldhaber. Only they can create top-level comments. Comments here also appear on the Quick Takes page and All Posts page.
Depression as a concept doesn't make sense to me. Why on earth would it be fitness enhancing to have a state of withdrawal, retreat, collapse where a lack of energy prevents you from trying new things? I've brainstormed a number of explanations:
I'm partial to the explanation offered by the Predictive Processing Model, that depression is an extreme form of low confidence. As SSC write:
imagine the world’s most unsuccessful entrepreneur. Every company they make flounders and dies. Every stock they pick crashes the next day. Their vacations always get rained-out, their dates always end up with the other person leaving halfway through and sticking them with the bill.
What if your job is advising this guy? If they’re thinking of starting a new company, your advice is “Be really careful – you should know it’ll probably go badly”.
if sadness were a way of saying “Things are going pretty badly, maybe be less confidence and don’t start any new projects”, that would be useful...
Depression isn’t normal sadness. But if normal sadness lowers neural confidence a little, maybe depression is the pathological result of biological processes that lower neural confidence.
But I still don't understand why the behaviors we often see with depression - isolation, lack of energy - are 'longterm adaptive'. If a particular policy isn't working, I'd expect to see more energy going into experimentation.
[TK. Unfinished because I accidentally clicked submit and haven't finished editing the full comment]
Since we can sequence genomes we know how many changes need to happen for the difference between organisms. We know that gene drift destroys features for which there isn't selection pressure to keep them like our ability to make our own Vitamin C.
It seems to me like the moving pieces that are needed for computer models are there, so I would trust experts opinions of people on the topic more strongly then would be warranted 30 years ago where opinions were mostly based on intellectual arguments.