r/fatlogic derail

It's 1am so the numbers will habe to wait but on hibernation:

Because mammals who do this put their entire metabolism into absolute minimum use because they're adapted for it. Humans aren't. Our metabolicpathways for many things are different, see the fact that we can't synthesize VitC but most other mammals can.

AS for 'eat less than you burn' that's the difference between your BMR and total expenditure. The total is mostly determined by exercise and where fat burning happens. The BMR is your minimum requirements just for staying alive.

Anyhow more Details tomorrow

 

turtledove: I may be a CS major but I was raised by a doctor. Don't make assumptions about what I'm able to usefully read about.

 

Re: Hibernation. Has anyone else heard that Seasonal Affective Disorder might have been a useful trait back in pre-agricultural times? Everyone just huddled together and staring at the walls for most of the winter would cut down on energy needed.

 

I've .... never encountered that idea before, can't find any source for it, and am honestly baffled by it.

 

I think when you have SAD, you're still using as much energy as ever, you just can't do as much with it. Plus humans did the bulk of our evolving near the equators, anyways.

And you still need to do things in the winter! You need energy to keep yourself warm, you need energy to catch food and prepare it, to take care of the young and the elderly and the sick, to repair tools and clothes - having a 'sit down and watch the walls' mode is the worst parts of 'stay awake and aware the entire winter' and 'hibernate' with none of the benefits of 'continue to get shit done' or 'go into reduced energy consumption mode for the Meganap'

 

I've heard about the idea of "this might have been a useful trait back in pre-agricultural and early agricultural times", yeah, but what I heard it being referenced for was bipolar disorder - specifically the long cycle variant, where the mania would (ideally) be happening during the spring and summer, when there's a lot of work that can be done outdoors to help prepare for the coming winter. Then during the winter, depression-napping might help conserve energy or at least help stave off cabin fever, especially since a lot of tasks (repairing tools and clothes, making tools and clothes) can be done on a 'when you have spoons for it' basis and a lot of foods at the time would have had long cook times (which allows for sitting things in a pot and just letting them do their thing). An absence of mania would certainly have helped prevent the urge to go outside and do anything.

Also the fact that most other mammals who're carnivores or omnivores are also adapted for feast-or-famine diets, and can safely go a couple weeks at least without eating. Humans are not adapted for feast-or-famine diets any more, and our metabolisms tend to operate on the assumption that we're going to be getting food at least every few days.

Do feel free to point out where I was making assumptions. What I saw was:

which looks a lot like you stating that you don't know how those things work. And definitely looks like you arguing with a biology major about how the human body works, when they just told you (twice!) that your premise for "hey, the brain should be fine if you're running off fat reserves alone" is not something that would work in practice. That you were raised by a doctor has nothing, afaik, to do with whether or not you were asking for a layman-comprehensible explanation from someone you are - in the exact same post - arguing with.

In fact, what I specifically said was

Which isn't me saying you're unable to usefully read anything. It's me saying that you're engaging in a behaviour that doesn't look good. Being snarky at me about it doesn't change anything.

 

I certainly haven't, and considering human evolution, it doesn't make sense anyways. We did most of our evolving in equatorial or near-equatorial regions, where seasons as such are much less of a thing and stuff like rain/dry times are much more impactful than relatively small changes in light cycles.

Hinging on that: not everything that happens to humans has to be 'evoltionary sensible'. It's likely and even built into the concept that variation within the population just happens. As long as those variations aren't 1) deadly enough to take the carrier out before they can reproduce sufficiently 2) not beneficial enough to allow the carrier to outbreed people without the variation it will just continue to occasionally show up.
in relation to that: something are just logical followups to other things. We need VitD for a whole number of bodily functions, brain function included. Not getting enough will therefore impact brain function one way or the other. Personal variance here comes in at 'how much can the body cope with before showing symptoms' and 'how easily do we produce VitD under certain conditions'.

The only reason WHY there's pale skinned humans today is that in the northern hemisphere, in the absence of a diet rich in fish and certain meats (which contains VitD!), pale skin makes for better VitD production'
That's the entire evolutionary pressure behind it and also the reason why a number of indigenous people of the arctic circle are not pale. Being able to compensate through diet means they never had to acquire the paleness adaption.

 

Ah, yes. I forgot a bit of the details in how evolution works. There is an easy experiment to see if that theory even warrants further attention. If SAD is present in African-Americans, then it was just a random quirk. If it's confined to certain populations, it might have been a quirk that did more good than not, or it still might be random.

Just another random thing I've heard. Vitamin-D
absorption is a problem for African-UK, and really shows up in cases where a breastfed child has weak bones.

 

Generally speaking, whenever someone says that a particular mental illness was ~actually really useful~ for our evolution, it's a tenuous argument at best and total BS at worst.

*ETA* I get the impression that it's often motivated by a desire to feel at peace with one's issues, especially if you feel you're strongly genetically predisposed to them.

 

A condition which makes people kill themselves is not going to be evolutionarily helpful.

 

also, like... pre-agriculture means you don't have as much food stockpiled, you have to keep hunting and gathering all winter long. and foraging is harder in the winter, since there are fewer edible plants available-- it takes MORE energy to survive a winter, not less.

edit: this is all assuming you're living in an area that even HAS an appreciable winter, of course. as noted, humans evolved in sub-saharan Africa, where rain cycles have much more to do with food availability than an hour more or less light a day.

 

Well, that's not necessarily true. It could easily be associated with other beneficial traits (e.g., the genes that cause it also do things that make an individual successful in their environment). As long as people reproduce before they die, evolution doesn't "care".

 

Didn't think it did care, my point was more that dead people don't reproduce.

 

Not really, in the case of humans. Or else, the average lifespan would be the same as the time of meno/andropause. Social mammals in general usually outlive their direct reproductive usefulness to care for other members of the group.

 

Yes... But it depends when they die and what is linked with the trait that you claim is disadvantageous. That's my whole point. If in general people are reproducing before they kill themselves, then it's evolutionarily neutral.

 

Everyone wants to fight with the people with specific training in biology, including the one who is literally studying evolution.

 

What about caring for, say, your grandchildren? (Also, I should also point out things like the gay uncle hypothesis, in terms of "caring for other people's offspring)
Also, andropause is a thing, but it's a drop in fertility associated with lowered testosterone, it doesn't make people completely infertile.

 

That's why chorea-huntington hasn't died out yet (well that and the whole issue with treshhold mutations)
The problematic onset of the illness happens /after/ people have typically already reproduced making it evolutionary neutral despite the obvious drawbacks.

 

My thought was SAD is as likely to kill you before you've reproduced as after, but then that early in the evolutionary tree reproduction would be happening earlier than it does now anyway.