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Comment by hh3k0 | Hacker News Reader

> I have long had the hunch that depression (and especially SAD) make sense from an evolutionary perspective as a sort of hibernation strategy.

Interesting, I've long had the hunch that an evolutionary purpose of depression could be to strengthen a tribe by weeding out individuals that are a burden to said tribe, as self-perceived burden seems to be closely linked to the disorder.

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That doesn't float. Natural selection can never select for suicide to benefit the group, unless the group is genetically identical - such a trait simply isn't adaptive.

Natural selection of whole group does make sense if they are genetically related (and you consider the fact that in addition to individual dying off, it is possible for whole groups to die off (over longer time scales))

Kin selection: https://en.m.wikipedia.org/wiki/Kin_selection

I have no idea if it applies to depression. I don’t really buy the simple story from GP.

I think you might be combining Darwinism with Dawkinsism here.

Natural selection isn't necessarily preservational of individual genes (nor of genotypes). It just argues that the survivors are more genetically fit for survival. This aligns with GP's comment.

The Selfish Gene theory argues that behaviours among the group tend toward preservation of the genotype. Family over strangers, generally.

I do take issue with GP's "evolutionary purpose" -- these two words cannot be combined in a meaningful way. But, interpreted as "evolutionary contribution", it could make sense.

All that said, I also don't think that GP's idea floats, nor does it hold water. Genetic predisposition to depression is very poorly understood, but seems (to me) to be just ordinary phenotypical noise in the signal. Quasi-random variation which is to be expected in any sufficiently complicated system.

You're looking at it from a very individualist perspective. In reality, genes don't belong to the individual, or a tribe or species for that matter. Genes belong to the ecosystem i.e. genes favor behavior which is good for the fitness of the ecosystem (you could say it's because of the other way around, but you get the idea), even at the expense of the individual itself or other lower level organisms or super-organisms. It will be clear if you look at it from a different perspective. White blood cells kill bodies own cells all the time. If you think the reason might be to protect the larger organism, it makes more sense. But there's more.

Think of the "freeze" response that, say, deer have when they get caught by a leopard. It would be best for the deer (and its family i.e. those with similar genes) if it didn't have a freeze response. It would be much better for them if they had a "fight till death" response. That way, every time a leopard caught a deer, it would get most likely get injured and leopards would be able to hunt fewer deer.

The deer has a freeze response because it has nothing to do with what's good for the deer and everything to do with what is good for the ecosystem. It's best if it outruns the leopard... but if it gets caught, it's best if it freezes while the leopard kills it.

P.S. The mainstream explanation of the freeze response is that "it helps the deer deal with the pain". However, they fail to explain what the evolutionary benefit to not feeling pain as one is being eaten is.

>genes favor behavior which is good for the fitness of the ecosystem

No, they don't. That's simply wrong. They favor their own survival.

And you really didn't need to post this twice.

That view is too teleological, as if there's a "better". I could see both being advantageous, depending on conditions. The "hibernators" would have a caloric or metabolic advantage should there be harsh conditions and little need to go out and face said conditions when finding food would essentially be fruitless. But given modern conditions that's not quite as advantageous now though could be in the future should we have caloric restraints and one's presupposed to "hibernating" the metabolism to some extent.

Depression != suicide. Depressed people don't usually kill themselves, even under modern circumstances where suicide rates are elevated because means of easy suicide are widespread[1].

1: https://med.stanford.edu/news/all-news/2020/06/handgun-owner...

> The lifetime risk of suicide among patients with untreated depressive disorder is nearly 20%. (Gotilb I, Hammen C. (2002). Handbook of Depression.)

https://www.dbsalliance.org/education/depression/statistics/

I'd call that significant, particularly considering the pace of evolution and how recently mankind started treating depression.

That being said, a (self-perceived) burden can free the tribe from their own weight without suicide: social withdrawal and isolation are fairly common in depression.

But as I said, that's just something I've occasionally pondered about. I might be wrong about it, as other users have already pointed out.

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