Human Evolution and Obesity ???

[Havok]

I was thinking about this and figured I would get some input from all you smarty pantses.

Assuming obesity becomes an overwhelming problem outside of the US as well as it is in it right now, and it becomes a world problem, how would the evolutionary process handle it?

The first idea I had would be that in order to deal with the extra weight that our lifestyles (lots of food, no exercise) create, the human body would eventually adapt by making us taller and wider to more evenly distribute the weight, as well as making us stronger over all, bones, muscles and especially joints) to deal with it as well.

The other idea I had, was that the metabolic process would adapt and would speed up and increase to keep us in the optimal weight ranges that humans have traditionally been in.

Are either of these realistic outcomes of our current path, or are we just going to eat ourselves do death? Any other ideas on what may happen? I'm certainly not even a dabbler on the topic of evolution aside from saying "Yes it is real and a fact", so is this even a feasible function of it?

Thanks for indulging me.

[Darth Wong]

You realize that the obesity problem affects only a very small percentage of the human race, right? The United States is not the entire world.

[Havok]

You realize that the obesity problem affects only a very small percentage of the human race, right? The United States is not the entire world.

Uh, yes, which is why I wrote... "Assuming obesity becomes an overwhelming problem outside of the US as well as it is in it right now, and it becomes a world problem, how would the evolutionary process handle it?"

There was just an overwhelming parade of fat assed people (like myself ) coming into the dealership today. I really don't think there was a single skinny or even average weight customer that came in.

I guess this is a "The World Gets Fat" RAR (I think that is what that means)

[SpacedTeddyBear]

It's kind of hard to say since evolution isn't an "active" process. Nature won't automatically mutate genes here and there to compensate because several generations of a certain species decides to get fat from whatever their vice is.

So unless some random mutation takes place in a person that produces dominate traits that allows an overweight person to be able to cope better with with the added stresses on the body, then you're shit out of luck.

[Darth Wong]

You realize that the obesity problem affects only a very small percentage of the human race, right? The United States is not the entire world.

Uh, yes, which is why I wrote... "Assuming obesity becomes an overwhelming problem outside of the US as well as it is in it right now, and it becomes a world problem, how would the evolutionary process handle it?"

But it can't become that kind of problem, because the world cannot produce the kind of extravagant wealth and food output that could possibly extend this problem to the entire human race.

[Superman]

The first idea I had would be that in order to deal with the extra weight that our lifestyles (lots of food, no exercise) create, the human body would eventually adapt by making us taller and wider to more evenly distribute the weight, as well as making us stronger over all, bones, muscles and especially joints) to deal with it as well.

I believe you're thinking in what's known as Lamarckian terms. Jean Lamarck was an early evolutionary theorist who believed that evolution basically occurred when the environment dictated that an organism must somehow improve to survive. I believe one of his illustrations involved a giraffe. He pointed out that since the leaves giraffes prefer to eat grow on the tops of taller trees, "fluids and forces" changed the giraffe by giving it a longer neck over time.

Biologists now know that this isn't quite how evolution works. In the case of the giraffe, you really have to look at its entire population. The stronger and most fit giraffes are the ones who can reach the leaves that are higher up. These giraffes might also gain some nutritional benefit by eating these leaves as well. These are also the individuals who will produce the most offspring, thereby passing along the genes that will produce offspring which resemble the parents.

So my point is that evolution, or rather natural selection, isn't going to "deal" with a population of obese humans. Humans would end up with more health problems, and rely more heavily on modern medicine to deal with them.

[Darth Wong]

I think what a lot of people don't realize about evolution is that it is based on death. In order for evolution to work, you need to be killing people off. So unless the fat half of the population murders the skinny half of the population, we won't see the human race becoming optimized for fat-assitude. And the same advances in medical technology and personal assistance technology which make it possible for fat people to live would also make it possible for fat people without these hypothetical changes to live.

[Superman]

I think what a lot of people don't realize about evolution is that it is based on death. In order for evolution to work, you need to be killing people off. So unless the fat half of the population murders the skinny half of the population, we won't see the human race becoming optimized for fat-assitude. And the same advances in medical technology and personal assistance technology which make it possible for fat people to live would also make it possible for fat people without these hypothetical changes to live.

I think Sagan once said that 99% of all species that have ever existed are now extinct, which makes perfect sense.

[Havok]

I believe you're thinking in what's known as Lamarckian terms. Jean Lamarck was an early evolutionary theorist who believed that evolution basically occurred when the environment dictated that an organism must somehow improve to survive. I believe one of his illustrations involved a giraffe. He pointed out that since the leaves giraffes prefer to eat grow on the tops of taller trees, "fluids and forces" changed the giraffe by giving it a longer neck over time.

Biologists now know that this isn't quite how evolution works. In the case of the giraffe, you really have to look at its entire population. The stronger and most fit giraffes are the ones who can reach the leaves that are higher up. These giraffes might also gain some nutritional benefit by eating these leaves as well. These are also the individuals who will produce the most offspring, thereby passing along the genes that will produce offspring which resemble the parents.

So my point is that evolution, or rather natural selection, isn't going to "deal" with a population of obese humans. Humans would end up with more health problems, and rely more heavily on modern medicine to deal with them.

I think what a lot of people don't realize about evolution is that it is based on death. In order for evolution to work, you need to be killing people off. So unless the fat half of the population murders the skinny half of the population, we won't see the human race becoming optimized for fat-assitude. And the same advances in medical technology and personal assistance technology which make it possible for fat people to live would also make it possible for fat people without these hypothetical changes to live.

See, this is the kind of info I wanted from this. Like I said, I am not well versed in how evolution works aside from a few readings here and there and ths type of feedback helps me expand my thinking and go "Oh right. Duh!" on all the stupid "what ifs" that scramble through my mind.

I do however, want to subscribe to your idea of Optimized Fat-Assitude Mike.

Again, thanks for indulging me.

[Lusankya]

You could argue that since obesity leads to fertility issues, then people who are less disposed to gaining weight will outbreed those who are more disposed to gaining weight. Of course, this will be a minor discrepancy, so it would be a while before it made a noticeable impact on the population as a whole, and given the number of other selective pressures in the environment, I doubt it would be that significant.

[Superman]

You could argue that since obesity leads to fertility issues, then people who are less disposed to gaining weight will outbreed those who are more disposed to gaining weight. Of course, this will be a minor discrepancy, so it would be a while before it made a noticeable impact on the population as a whole, and given the number of other selective pressures in the environment, I doubt it would be that significant.

That would be true, except for the fact that we have modern medical technology. One example I've always thought about is all the food stamp collecting white trash types. As a whole, these are people who tend to have the most mental problems, the most physical health problems because of their lifestyle choices, lower intelligence, they tend to get involved in crime and the penal system, etc., and in this day and age (at least in this country) they outbreed everyone else. 100,000 years ago, natural selection would have taken care of much of this problem... but in this case, natural selection has sort of been defeated by our human ingenuity.

[Lusankya]

That would be true, except for the fact that we have modern medical technology. One example I've always thought about is all the food stamp collecting white trash types. As a whole, these are people who tend to have the most mental problems, the most physical health problems because of their lifestyle choices, lower intelligence, they tend to get involved in crime and the penal system, etc., and in this day and age (at least in this country) they outbreed everyone else. 100,000 years ago, natural selection would have taken care of much of this problem... but in this case, natural selection has sort of been defeated by our human ingenuity.

Oh, I agree. With all the social issues related to family size, I wouldn't expect fertility issues to do with obesity to rank high on selective factors. I'm also somewhat sceptical about whether or not this era of high food availability and low need for physical activity will last long enough to be particularly relevant in the grand sceme of things. I was just throwing an idea out there.

[Junghalli]

The most likely result (assuming no major medical breakthroughs or anything) is that people with genetic predispositions to gaining weight in a food-rich environment would tend to be more likely to die of heart attacks, diabetes complications etc., which would create a selection pressure toward lower genetic predisposition for gaining weight.

Interestingly, in modern society we see what might be a sexual selection effect against obesity, with skinny people generally being thought of as more desirable. This is undoubtedly purely cultural, at least at this point, but it may also create a selection effect against genes that promote obesity.

[Broomstick]

That would be true, except for the fact that we have modern medical technology. One example I've always thought about is all the food stamp collecting white trash types. As a whole, these are people who tend to have the most mental problems, the most physical health problems because of their lifestyle choices, lower intelligence, they tend to get involved in crime and the penal system, etc., and in this day and age (at least in this country) they outbreed everyone else. 100,000 years ago, natural selection would have taken care of much of this problem... but in this case, natural selection has sort of been defeated by our human ingenuity.

What most people miss in your example is that such types - uneducated, in the penal systems, etc. - are also the people most likely to get into situations where they die by violence or accident. Crazy/mentally dysfunctional people are also more likely to die by accident or crime. The question isn't "are they producing more babies?" but "are they leaving more descendants?" Not sure I can answer that one.

But, back to the OP - RAR! We have a world of fat people that form a stable breeding population. Nevermind for the moment how we got there, the question is, what effects will we see with a combination of obesity and evolutionary pressures.

Remember, evolution is all about how many descendants you have that also have descendants. Not so much a matter of children but grandchildren. If a woman births 18 children but they all die by the age of 5 from an evolutionary perspective she might as well be sterile. Only the kids that grow up to have more kids count.

So... the cons of obesity include reduced fertility, early death, heart problems, diabetes and its long list of complications, and less sexual appeal.

Hmm... well, the "less sexual appeal" will certainly reduce evolutionary fitness by way of sexual selection but if everyone is fat enough people will probably overcome their reluctance to to maintain a breeding population. This will tend to favor the less obese over the more obese, so any genetic component to lessening obesity in a fat-producing environment will be favored.

Early death from heart disease and/or diabetes will only have an effect if it kills you BEFORE you breed. High body fat is associated with early puberty. Even in very fat people, death from complications seem to hit after 30. Start producing children in the teen years (which human bodies are very able to do) and you'll still likely live long enough to raise the children even if you aren't living past 30 or 35. Even if fat kills you before 25 you still have a chance to pop out a few kids before you expire, and as long as those kids are able to do the same evolution is not eliminating your family line with its tendency towards extreme girth.

Alright, what about favoring the skinny? Skinnier people, assuming they are thin because they're healthy, will tend to be more fertile, will be able to breed more years of life, and will be better able to take care of those children which will tend to make the chances of offspring growing up to be healthy and leave more descendants higher. If the differential between skinny and fat reproductive rates is great enough over time the skinnies will tend to outbreed the fatties, although it's unlikely either type would wholly disappear because, after all, the fatties are living long enough to produce some children.

But as for the human body "adapting" by developing heavier bones, bigger muscles, etc.... no, I don't think so. The easiest way to deal with too many calories (other than eating less) is not re-engineering the body but simply by making digestion much less efficient. So a trait that results in poor absorption of nutrients would result in a skinny person who escapes the complications of obesity without having to change everything else. Just a tweak to the intestines would probably do the job. Also, any genetic traits (as opposed to cultural or learned traits) that result in smaller appetite or different food preferences leading to fewer calories ingested would also be dispersed over the generations as well. Of course, then you might get the occasional person with malabsorption, no appetite, and a liking only for lettuce dying of malnutrition/starvation because evolution doesn't care about the individual, only that enough of a group survive long enough to leave descendants. From the perspective of evolution it doesn't matter if you have a short life full of pain and suffering as long as you leave grandchildren.

Likewise, unless you're suggesting a society where people are SO fat as to die of complication by the mid-teens, thereby cutting off possibility of reproduction, you're never going to see the fatties disappear.

[Durandal]

What will probably happen is that segments of the first-world populations will, over time, adapt to high-calorie diets. We don't need to store fat for energy later as aggressively anymore, since we get a steady food supply year-round, not just during the Spring and Summer seasons. Before, we needed to store up fat for the Winter, when food would be a lot more scarce.

[Sarevok]

A related question...

Gaining weight fast is viewed as a detriment. People who can eat a lot without looking like Sumo wrestling trainees are envied.

However is the tendency to gain weight really a physical flaw ? In pre historic times food was scarce and people who got more out of less food would have an advantage. The naturally skinny people, the ones with inefficient digestion, would be dying more easily. So has an advantage for surviving in harsh hunter gather societies now turned into a disadvantage in an industrial society where food is plenty ?

[Junghalli]

However is the tendency to gain weight really a physical flaw ? In pre historic times food was scarce and people who got more out of less food would have an advantage. The naturally skinny people, the ones with inefficient digestion, would be dying more easily. So has an advantage for surviving in harsh hunter gather societies now turned into a disadvantage in an industrial society where food is plenty ?

Yes, that's exactly what happened. All our obesity problems are caused by the fact that our metabolisms and instincts are still designed for an environment where we don't know where our next meal is coming from.

[Plekhanov]

Seeing as in all but the most extreme cases obesity doesn't shorten peoples lives enough to stop them reproducing where's the selection pressure for obesity to affect evolution supposed to come from?

[Molyneux]

Seeing as in all but the most extreme cases obesity doesn't shorten peoples lives enough to stop them reproducing where's the selection pressure for obesity to affect evolution supposed to come from?

It doesn't have to stop their reproduction, just affect it negatively. If they tend to have only 1 or 2 children and the mean is 3 or more, they will still decline.

[Darth Smiley]

That assumes 'being fat' is 100% hereditary - which is not entirely true. Social factors make it so its more like 'person with Genome X will become fat in more situations than person with Genome Y'. So in order for there to be a statistically significant drop in BMI due to the effects of natural selection, you are looking at timescales on the order of thousands of years, minimum.

And, of course, we have assume humanity doesn't sometime in the couple thousand years
a) get killed off or knock back to the bronze age by nukes, asteroids, global climate change, etc.
b) get around natural selection entirely via uploading, cyborgization, or genetic engineering.

Which are two very big assumptions. So no - fatties don't go extinct.

[Plekhanov]

Seeing as in all but the most extreme cases obesity doesn't shorten peoples lives enough to stop them reproducing where's the selection pressure for obesity to affect evolution supposed to come from?

It doesn't have to stop their reproduction, just affect it negatively. If they tend to have only 1 or 2 children and the mean is 3 or more, they will still decline.

Does obesity even shorten peoples lives by enough to reduce the number of children they have? So far as I'm aware obesity rarely shortens peoples lives enough to kill pre-menopausal women or the years when men typically have children.

As for sexual selection so far as I can tell obese people may on average have to settle for lower status partners but they do still manage to hook up and reproduce.

[wjs7744]

b) get around natural selection entirely via uploading, cyborgization, or genetic engineering.

How about getting around natural selection by reducing mortality rates across the board, like we already have done? Is there any reason to believe that the mortality rate is high enough to even drive natural selection anymore? We may be well on the way to effectively ending natural selection in humans already, who says we need genetic engineering or fancy cyborg tricks to do so? After all, we have already basically stopped natural selection in a large variety of domesticated animals.

[Lusankya]

Does obesity even shorten peoples lives by enough to reduce the number of children they have? So far as I'm aware obesity rarely shortens peoples lives enough to kill pre-menopausal women or the years when men typically have children.

Obesity does have a negative effect on fertility. In fact, if a "larger" woman is having difficulty getting pregnant the first thing doctors will suggest is for her to lose weight.

As I've said before, however, I think that other factors play a greater selective pressure on humans than weight.