> Crying spells and slowed movements attract attention.
Only if you're already around people. Slowed movements put you in the path of fewer people, especially in a pre-modern environment (say, hunter-gathering). The natural inclination of a depressed person is, afaict, not to leave the house at all.
> Flat affect reads as ingratitude.
Only matters in a particular type of social environment, which a person suffering depression would likely rather avoid.
> Emotional deadening tends to leave you with the one emotion that will get you in the most trouble, anger.
This doesn't square with any account of depression I've ever heard. I think it's an entirely different kind of deadening.
And it's not about "submissiveness". If you're getting that from the one example in the article, I don't think you understood it. I think the theory is that depression is about avoiding negative stimulus/continuing damage/trauma. "Conformation" as the prime way to avoid damage, rather than staying out of the way of predators or, I don't know, conserving strength after an injury, is extremely modern. Depression can get behind sugar-craving in the line of things that just recently became maladaptive.