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Psychohistorian comments on What should I have for dinner? (A case study in decision making) - Less Wrong
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When people talk about diet, the phrasing often seems to be "fats are bad for you" versus "carbs are bad for you" or "this is bad for you" versus "that is bad for you."
The question that I came up with while reading this post was, why are these hypotheses in conflict? Why should there be an option that is "good for you"? Assuming that "eating" evolved by way of "things that eat tend to reproduce more" and "things that feel good when eating things that help them reproduce will eat them, feel good, and reproduce" (I realize that I'm abusing evolutionary explanations here but I will get to my point) I don't see any reason to believe that there exists a diet which will make people happy and healthy over the long long term.
On the one hand, the existence of food that would keep humans healthy significantly past reproductive age has only been selected for in the past 10,000 years. On the other hand humans that stay healthy past reproductive age have never been selected for (at least in men ).
So there's a lot of evidence that I don't fully understand in the background of this debate, and I have little to no knowledge of nutrition, so I'm hoping to learn a lot and change my mind at least twice based on replies, but...
So I guess my question is, do "mainstream" nutritionists maintain that carbs are good for you? Does Taubes maintain that fat is good for you? Does data suggest that there exists a diet which is good for you, that creates serious improvements in longevity and health?
This is a flat-out misunderstanding of human history. The existence of female menopause, plus substantial evidence from existing hunter-gatherer tribes, suggest that longevity is adaptive. In tribes studied, post-menopausal women gather far, far more than their daily calorie intake, helping their descendants by providing extra resources. The reason prehistoric man had a low life expectancy is more due to high infant mortality than dying early. If long lives were not evolutionarily relevant, the existence of human menopause makes even less sense than it currently does.
Menopause makes sense the way I've heard it explained. Being pregnant, or having a young dependent child, reduces the ability to care for preexisting children. This is so obvious in resource-poor cultures that infanticide (preferentially of weak or closely spaced children) has been commonplace through much of history. The drain on resources that a new child represents increases with age: it is easier and less costly to have a child while young. After a certain point, the expected extra descendants gained by the ability to bear more babies is less than the expected extra descendants gained by investing the pregnancy & subsequent resources instead in the last one(s) born.
That's the story I've heard too. I wonder just how many women in the relevant resource poor cultures aged long enough for it to matter.
That's the exact point. Menopause is very rare in the animal kingdom. The fact that it exists in humans shows that some portion of our ancestors lived long enough for it to be selected for to the point of total dominance in the population.
That's true.
The "don't bother with children when you are old" incentive is also helped along by the decreasing genetic value of children born to old mothers. The likelyhood of Down Syndrome is increased by an order of magnitude or two, for example.
I would like this whole comment thread a lot more if anyone linked to any studies or at least blog posts or books on amazon or something detailing where they got their ideas from (I don't mean to be picking on anyone I just have very little knowledge of the subject and I'm curious where people got their first notions of things like "there exists a good diet which will make people feel healthier and live longer by a significant margin")
My source is a book, and thus not terribly accessible. As Alicorn points out, menopause makes sense, but its existence strongly suggests enough women lived long enough for it to actually be selected for. It is not common in other animals.