Here’s a little something I’ve been thinking about recently and would like to see an intelligent debate on. Why does it seem (however subjective) that man the animal is becoming less fit for survival, when we have no reason to believe that laws of selection and the progression of evolution do not apply to us?
Let’s set a bit of a foundation for the discussion first. I’m aware that ‘Anti-evolution’ doesn’t exist per se. Just because an organism adapts in ways we don’t expect or understand, doesn’t make them mal-adaptive. I used the term to underscore the perception, but it’s not scientifically accurate. I am also aware that some people don’t believe evolution or selection occur at all – I’d be happy to debate that another time. For this discussion, the question is: If we are evolving, why do we observe the following?:
-The incidence of being overweight by an unhealthy margin is on the increase. [reported numerous time in the NEJM, most recently Mar 22, 2001] What benefit would outweigh the increased risk in cardio vascular and other diseases? [a correlation made in numerous publications, including the NEJM]
-My first thought was that, especially in more developed nations where the incidence of unhealthy weight is the highest [WHO study 1998], a greater emphasis on education and white collar industry was overshadowing the health aspect. But this raises other problems…
-Success at propagation is the tenet by which selection operates. So, if education and white collar success are the new adaptive traits, why do we find the birthrate higher among the less privileged and educated? [MIT study of 62 countries in 1999]
note: that these ‘adaptations’ have enough data attached to them that trends can be established and we can rule out the possibility that they are short lived flyers. I’ll save a couple other points and make them if the discussion gets rolling.
So what gives? Are we exempt from the law of evolution because we are sentient? I personally think not. For the better or for worse, we are responding and adapting to something, even if it has negative connotations for our society as a whole….
Overweight: You are failing to differentiate between a genetically caused increase in weight and an environmentally caused increase in weight. It is clear that the increase in weight is because people are eating more and exercising less, not because there has been a change in allele frequencies. The answer to this is that our bodies evolved in a different environment than we live in. Take all those fat out of shape office workers and put them to work hunting and gathering on the african savanna and the pounds will just melt right off.
Now, the inverse correlation between “success” and children. You claim that education and white collar success are the new adaptive traits. But that is not true. You can be the richest man in the world and if you don’t have kids, or perhaps help support your other relatives who do, then you are an evolutionary failure.
But so what? We can chose our own goals, we don’t have to work for evolution. Is the species better off if Bill Gates has 20 kids? I doubt it, especially considering that the mix of talents that has made Bill Gates the richest man in the world isn’t neccesarily going to make people successful in the future. Obsessive/Compulsive nerds may rule for right now, but will that be true always?
As I understand it, evolution generally means a species adapting to their environment and changing on a genetic level thus creating a new species. This is the best quote I could find from origin of species to illustrate it:
Our Knowledge base is increasing at such a rate that our actual bodies are becoming somewhat secondary. By this I mean we are creating a world where comfort is pretty much the primary goal(the changing environment). We are adapting to this by our asses becoming larger and our muscles weaker(as a whole) because they are not being used. This seems to coincide with the definition of evolution .
So to answer your question, we are in fact evolving, it just isn’t positive. In the definition of evolution it simply says “usually more complex or better form”. The key word there being usually.
Correct. But for this discussion does it matter? Unhealthy weight is in evidence. Neither genetically nor socially induced should it be favored by laws of selection… yet it is on the rise.
Correct. It was a possible hypothesis, but if you read my next point, you will note that I already debunked it. Higher education has a negative relationship with birthrate.
The conundrum is: what the heck are we responding to, if anything? Looking at the data would suggest that overweight and less educated are the favored traits.
Mayberrydan, my thinking is more in line with yours.
What Lemur said. We are not reponding and adapting. Millions of overweight people are evidence of us NOT adapting to a change in the enviorment. We are using the same old survival strategy - eat everything you can, partuicularly calorie dense fats and sugars- that worked great when food was scarce and appling it to a different enviorment where it no longer works.
When we start getting people with an innate aversion to saturated fat or something, then you could say we’re adapting- though it’s hard to see how that trait would arise and get passed on since people die young from being overweight, but not before they’ve reproduced. (And anyway, long before that has a chance to happen civilization will have collapsed and we’ll be back to subsistence living .)
We have changed our environment such that we can get away without as much physical labor as our bodies are adapted for. We have also changed our environment such that we can eat food in larger quantities and of different qualities than our bodies are adapted for. We have also developed a whole medical system that allows those of us who aren’t as well adapted to our environments to live and propagate anyways.
To a large extent, we are ideed exempt from the law of survival of the fittest, as we can change our environment before having to adapt to it.
We’re talking about a very short span of time here. The rise of a seemingly “counter-evolutionary” adaptation that lasts for a few hundred, or a few thousand, years is not evidence of anything.
Of course, the human species isn’t particularly old anyway. Many, many unsuccessful species lasted 10-15 million years and then died out.
Yeah, that’s my feeling. Any species may go any number of changes over time, but if those chages don’t actually affect he birh rate negatively, the chages don’t matter much. If you die two seconds after producing offspring it is only a “bad” thing to you because you die. Didn’t stop the offspring (this is an extreme example, of course, so treat it as such).
As well, our brains being such useful tool-controllers/implimenters that they are far outweigh a few genetic setbacks. Where we stand now, we may be on the brink of overpowering any genetic setbacks, provided people get over genetic manipulation and let it happen.
Just a nitpick - for humans it’s not just pumping out children, it’s the ability to care for those children for about 15 to 20 years too. Although in the industrialized world that maybe less important, since children are generally cared for after the death of their parents - still you could argue that they’re not cared for as well, and an early death does impact reproductive success.
The OP didn’t intend it, but the overweight example is interesting, because overweight is not something that significantly harms survival until well after reproduction. So you could say that there’s no reason to think we SHOULD evolve any kind of protection against obesity. But we have, actually - humans don’t find obese individuals sexually attractive and I assume they don’t reproduce at nearly the rates as “normals.” If that’s true it should eventually limit the proliferation of obesity in the population. It’s not an effect that would kick in until there’s a consistent surplus of food. But I’d lay odds that in a few generations you’ll see a dramatic drop in the rates of obesity.
I can imagine a scenario where early death of a parent may positively affect reproductive success - at least in modern developed countries where the physical wellbeing of orphaned children is more or less assured by state intervention. It is often stated (though I supply no evidence to its veracity) that children with poor parental support will be more likely to engage in unprotected sex at an early age. If true then this would lead the offspring of those who die young to themselves have more (possibly unwanted) children making obesity a reproductive advantage.
I think in general when discussing human evolution, there is a danger in confusing success in biological terms with human measures of success.
**There does seem to be a weird inverse correlation in industrialized nations between “social” success/status and reproductive success. So your point is taken.
But I wouldn’t apply that to obesity, since when I said obesity impacts after reproduction - I meant well after the children are grown for the most part. So obesity wouldn’t have a reproductive advantage from that perspective (the orphaned child = prolific parent theory).
Also my main point was that obese individuals are at an extreme reproductive disadvantage because their likelihood of having sex in the first place is smaller.
Sorry, that comment was not supposed to be directed at you, more at the discussion in general.
Point taken, though to really stretch a point, any factor (including obesity) which places stress on family members could have a negative affect on preventing unwanted pregnancies.
The point I was trying to make was simply that many of the preconceptions we have about what is ‘good’ may not be what promotes biological success. I would not want to have to defend any particular such hypothesis, including my orphan/prolific parent one, just be open to the idea that some such convoluted relationships may exist.
Unattractive people can surely find partners amongst the similarly afflicted? Perhaps society puts pressure on them to feel inadequate and avoid seeking partners, in which case you would be correct.
sheesh The people here at my office need to leave me alone so I can follow up on this topic…
Let me start by thanking Phobos Simple, concise, and above all, accurate.
Evolution is merely change, it is natural selection that would seem to dictate that positive changes are favored. But that is not to say it is our myopic view of what is positive and what is not.
Thanks also to jab1. Your sickle cell resistance to malaria is an excellent example of a trait that on the surface seems maladaptive and to defy the rules of natural selection, but upon investigation we do find an advantage.
Which brings me to my theory of how we solve the this riddle:
No data this time, just MHO. We aren’t talking about taking an individual, family unit, or even a small community and isolating them. If we did, we might be able to make better predictions about who will thrive and who will not. But man is a social animal, and our modern societies are larger and more complex than ever. I humbly submit that low education and prodigious birthrate is a viable strategy in the first world where healthcare, welfare, and other help from the larger community can be relied upon. Likewise, one can survive in a state of lower health (such as obesity) for many of the same reasons – minimizing the negative effects. The more educated, despite also helping pay the way for others, have a viable strategy as well. Though fewer in number, their children are offered more advantages and more chance to be successful within society. It’s a tenuous balance to be sure, but this is the picture I see.
I want to echo maralinn. Pervasive obesity among humans has not been around long enough for us to judge its merit, or lack of. Obesity isn’t really pervasive in the human race, but only in the West. For these reasons it doesn’t qualify as an evolutionary adaptation.
We won’t be able to witness evolution of any traits over our lifetime. As a species, we now are less hairy, we walk upright, etc. but how long ago was it when we were, well, hairy apes? A VERY long time ago. No appreciable change in our “hairyness,” for example, has been seen over the past couple hundred years. All these differences we appear to be seeing between us and our recent ancestors are not proof of evolution, but merely variation, a response to a changing environment.
Since we are human, we are very well acquainted with ourselves and are aware of the tiniest little differences, and therefore tend to exaggerate them.
It’s fun to speculate about whether as a whole the human race will become more obese, less obese, etc. but we won’t be able to observe the results of this change, not in our lifetime.
Traits occur randomly. They just happen, there is no purpose. Good, or bad. If good, they get passed on because their owners survive. If bad, they die off, and we don’t hear about them because those species disappeared.
It’s not like, “hey, all my enemies are on the ground, therefore I will evolve wings and survive.” It’s more like, “hey, all my enemies are on the ground,” and all those individuals with wings survive, whereas those without don’t. And hence the “wings” trait get passed on.
It’s fallacious to say they are a “response” to the environment, although the environment plays a role in determining which traits get passed on, but there is no cause and effect.
Someone can correct me if I am wrong, but aren’t humans living longer lives than any time in the past? The human mind is our greatest asset in our survivability, because we scarcely have thephysical skills (spped, strength, razor sharp claws and teeth) to survive without our ability to use our minds. And I don’t just mean weapons and such, but our ability to understand and combat those things which afflict us. Medical research, medications, and medical procedures are advancing at an amazing rate. In fact, we may be getting “fatter” because the “cost” is going down, so to speak.
Waverly, having many children and hoping some of them will live has always been a semi-viable strategy. ( beware the rabbit ). Having few children to give them advantages has also been a semi-viable strategy (and also beware the elephant. )
But, just because something is happening, doesn’t mean that there will be an evolutionary “Reason” for it. As many people have tried to tell you, low health ( and, in some cases, your hot button topic, obesity ) is less affected because in the world we live in, you don’t die because of it. As a very easy example, we have no predators – if we did, people of lower health would be killed, and therefore we would evolve more. But, since we have no predators, people of lower health can live longer. This doesn’t make it an advantage, just not a disadvantage. As a further example, 100 years ago, diabetes was somewhat less common – because poeple who had it died immediately. Now, you can live with it, and reproduce – so having diabetes is no longer being selected against. But, there isn’t a “Reason” for diabetes – I can’t think of anyone who thinks there are benefits for it, but the disadvantages aren’t enough to kill you. As you mentioned, natural selection would seem to dictate that positive changes are favoured – but without selection ( read death *), those positive changes don’t come about.
And, people who are more educated have less children, true, but many of them have NO children. They aren’t doing it as a viable evolutionary strategy – they are doing it becuase they just plain don’t want children. Trying to find an evolutionary advantage for not having children is just plain laughable – as humans, we are too complex to do things only because of evolution. It would be like trying to figure out an evolutionary reason for Velvet Elvises!
Me’Corva
(* Yes, I know that it can involve sterilization, lack of ability to provide ( in some cases ), etc, but I’m trying to simplify )
**Tretiak[/b,] I believe that statement is correct, however length of life is not generally considered a direct measure of success. Speaking only in scientific terms, living beyond the years in which you have and care for children is a needless drain on resources (excepting the possibility of caring for grand children, etc.)
MeCorva
I eventually agreed with this point:
The reason I didn’t admit to agreeing with this earlier was that I was looking for an opportunity to post my idea that the effect of society must be considered. I didn’t mean to appear dense. I also don’t mean use the word ‘obesity’ in an offensive manner. It makes a good example because of the large amount of data on both trends and health implications.
On this, I disagree. We can make all the conscious choices we like, but in the [very] long run we will bend to the rules of selection.
.)