That's precisely why the "nature intended us to" argument doesn't really work for me when I hear people trying to convince me to try the Paleo diet. Whatever the benefits might be (besides making the author of those books a good chunk of money), they can be garnered by other means. What I hate even more is when a few devotees of such diets go on a slant about vegetarianism/veganism etc. etc.

I went from being a vegetarian to the paleo diet (or, actually, the "primal" variant). I thought about making this really long, but instead, realize that primal/paleo people use the primitive human as a model, a "common sense" starting base, and then apply liberal amounts of scientific knowledge to get a working solution.

It has changed my life. When I follow the diet, it has been pretty impossible not to lose weight. That's with eating as many eggs, as much butter, and as much natural, delicious, other whole foods as I can stuff myself with.

Second this. I am as critical as anyone of the naturalistic fallacy, and don't generally subscribe to the idea that what worked for cavemen will work for me.

However, the metabolic science is there if you read it, and I can't argue with the profound effect switching to a diet based on meat, eggs and other sources of saturated fats has had on my body.

I eat as much as I want, whenever I want, I'm never really hungry any more, and I've been losing fat and gaining muscle without thinking about it at all. It's pretty incredible.

A good friend of mine made the same transition (vegetarian to paleo) and says the same: it changed his life.

Not only that, but our "nature" has changed considerably since those times. Evolution has been far faster, likely 100 times faster the past several thousand years than it was before civilization. 15,000 years ago, nobody was lactose tolerant, nobody had blue eyes and who knows what else was different.

That isn't evolution, it is a diversification of our genetics. There are lots of things that many humans are intolerant to which would have probably been a really big weakness in the past.

Humans are no longer subject to natural selection. There needs to be significant culling pressure for real evolution to happen.

It is evolution, and it speeds up with higher populations. As for natural selection, consider that only small changes in allele frequencies add up quickly through the generations. Also, sexual selection is very much a force.

http://www.scribd.com/doc/33322719/Cochran-Gregory-10-000-ye... http://www.nytimes.com/2007/12/11/science/11gene.html http://www.wired.com/wiredscience/2007/12/humans-evolving/

"Humans are no longer subject to natural selection."

What? Are you sure? Because we most certainly are subject to natural selection.

Yes. But not to any significant degree that will cause a change as a species.

I'm sorry, but anyone who says this has failed to understand evolution.

Evolution is a slow process. But there is no reason to believe that it is going any slower today than it ever did in the past - we're just being selected for different things than in the past. (For instance carelessness about birth control.)

No, he's right. The most powerful force shaping the future is intelligence. Natural selection on biological genes is orders of magnitude slower.

The fact that intelligence is shaping our future faster than evolution does not affect the fact that evolution is still proceeding at the current moment in our species.

No, he's wrong. Natural selection doesn't speed up or slow down, it just is. Each passing generation there are pressures put on the spreading of human genes, and those pressures are the manifestation of natural selection. Whether those pressures are different now than before, or whether they shape "the future" is irrelevant to the biological impact of natural selection.

Sure it does, in the sense that there are fewer selective pressures on us, and those pressures are weaker. Our intelligence is able to overcome many of the pressures our environment exerts on us.

I'm highly skeptical that there are fewer selective pressures. One example, aren't industrial countries having fewer and fewer kids?

Just to clarify, When I say "us" I mean the western world. True, industrial countries are having fewer kids, and thats an example of a new selective pressure. It's a result of a new environment we've created for ourselves. I'm sure there are many to go along with that. But the sheer number of (potential) selective pressures we've removed through technology doesn't compare: many diseases, muscle size, brain size, vitamin D synthesis (its put in everything now), body hair, skeletal structure, the list goes on. Our interaction with our environment is on such a fundamentally different level that there are many classes of environmental pressures that simply don't affect us anymore.

Think of it this way: we used to be directly reliant our the environment for survival, like animals are. But now, we process our environment to such an extent that small variations in it are overcome by our intellect. Those variations in the past would constantly be exerting selective pressure on us in many different directions. Those pressures are processed out now.

we most certainly change as a species. Something as simple as choosing who to reproduce with affects the distribution of genes that are passed on to the next generation.

A more obvious example of the sorts of changes we can still go through is sickle cell.

Natural selection is just one component of evolution. Genetic drift and, especially, artificial selection are certainly in full swing.

And anyway, I completely disagree that we're no longer subject to natural selection. We're always subject to natural selection. We're not immune to everything.

Actually, everybody was lactose intolerant 15,000 years ago: http://en.wikipedia.org/wiki/Lactose_intolerant#History_of_g...

"15,000 years ago, nobody was lactose tolerant"

Ugh, sorry, yes. Totally misread that.

Us not readily acquiring the malaria virus is not due to evolution of our genes; we just don't live in the areas where the vector thrives. If you and I were bit by an infected mosquito, there's a very good chance either of us would die in a relatively short period of time. Although, there are some in Africa who do have fewer chances of acquiring it due to them being heterozygotes for sickle cell anemia.

Anyway, I'm not discounting the underlying concept of your comment; I'm just saying that malaria wasn't a particularly apt comparison.

I think the point is that we don't fight it "natually", we fight it with medicine and vaccines. We also have access to clean water which, if we did get malaria, would prevent us from dying from rapid dehydration(which in my understanding is the primary cause of death from malaria.) This is the argument against the caveman diets...

The primary reason we don't die from malaria is none of the above: it is mosquito abatement via intentional habitat destruction and copious use of effective pesticides. Large portions of the US used to be malaria country: not a spe mof it is now, and if there was a malaria outbreak in a US suburb we would wring our hands about the consequences for about five minutes and then dump enough chemicals on that subdivision to save an African country.

Ditto Europe, by the way.

I believe the strains of malaria that existed in North American and Europe were far weaker than the African varieties, though

Medicine is a fine way to treat things like infectious disease, but our western use of it is particularly useless (and often harmful) at treating long term "lifestyle diseases" -- stuff like diabetes, heart disease, and cancer. Prevention is far more effective, and diets that consist mostly of "food as grown" with minimal processing and alteration are good prevention.

> we just don't live in the areas where the vector thrives.

Actually, an awful lot of us do. I see those fucking Anopheles mosquitoes on a regular basis, especially if I venture a bit north from here.

> If you and I were bit by an infected mosquito, there's a very good chance either of us would die in a relatively short period of time.

Actually, out of the 225 million cases of malaria per year, there are only about 1 million deaths.

I'm not discounting the underlying concept of your comment; I haven't gotten malaria yet because of public-health measures like draining swamps, because of cypermethrin on the walls, because of DEET on my legs and head, because of sleeping under a mosquito net or in a room without entrances for mosquitoes, because of sleeping during the day, and because I have enough leisure time to swat the mosquitoes that do land on me.

I disagree with your statement about dying in a short period of time if you catch malaria. I grew up in a country with a high malaria rate (Papua New Guinea). I caught malaria several times and didn't die. Malaria is a curable disease, all though it is evolving against the current cures.

It's definitely curable. My hypothetical was based on the assumption that treatment was not given to show that we actually have not evolved defenses against the virus.

It's not a virus, it's a protozoan parasite, Plasmodium falciparum.

I'm not arguing what "nature intended us to" do (the human body is more adaptable than what the advocates of the Paleo diet take into consideration). I'm referring more to certain people with health problems who eat mainly fast food or food from the box and barely eat an apple a week. I know a few people who are like this and they end up stressing themselves by sticking to some draconian diet to get healthy.

I'm saying there's no need to stick to some strict diet, just eat a wide variety of foods instead of just one subset. The whole "think like a primitive man thing" is just a helpful starting point to point you towards what kinds of food to look for, but I'm not advocating some strict following. I had three In and Out dinners this past week since I'm too short on time to hunt down a pigeon or pluck mysterious fruits from trees all day.

The difference here from malaria would be that our bodies evolved, adapting to the nutrients that we were getting. We're more efficient on them -- more capable of living 'natural' lives.

[Of course, whether a 'natural' life is desirable is debatable.]

Malaria, however, we attempted to evolve away from(sickle cell anemia).

It's more that we're taking health risks by eating novel foods (things that weren't available as we evolved). There is a lot of evidence that insulin response is responsible for metabolic syndrome. There is also some evidence that the lectins in grains promote malabsorption of dietary nutrients.

Only time I'm satisfied with the 'nature intended us to' argument is some combination of walking/running. The way a good, smooth runner's body flows when they hit a fast jog screams to me "my skeletal and muscular structure was built for this!" Otherwise, yeah, as best I can tell adaptability is our only real designed-in-feature.

We're not as fast as most animals out there, but I don't think that means we didn't run a lot in prehistory.