Let's say they invented a "Jetsons" food pill. It supplied perfect nutrition and they are all designed around individual nutritional needs. All scientists/dietitians agree that eating these pills instead of real food will make you healthier and live much long. Would you not take the pills because "cavemen didn't eat food pills" or "this tribe doesn't eat pills"? You might continue to eat food because you like it ... but anyone using cavemen or indigenous arguments would be a fool. It's no different with our diet today. It doesn't matter what people used to do (or continue to do in third-world areas).
Yea but we don't have a Jetson's pill. All we have to go on is looking at the nutritional intake of humans throughout evolution to give us insights as to the proper type of foods we should be eating now. Part of knowing what would be in the Jeston's food pill is knowing what makes us healthy, and why. Here again we can look at evolution to give us clues. People, just like all animals, should be eating the types of foods they evolved to consume. Dogs don't eat grains in the wild, but some birds do. Rabbits don't eat meat, but cats do. When you give an animal (humans included) foods it isn't evolved to eat, its health can suffer (or even kill it) In a proper, balanced eco-system predators and prey will tend to consume food types suited to their bodies. Figuring out just how humans fit into that equation is the reason for looking back at how ancestors ate for millions of years (moving from proto-human vegetarians to advanced meat eating modern humans using tools and fire.)
Of course looking at what ancient humans ended up eating isn't the whole story, its just one aspect. If early man had access to Oreos he would have consumed them as well. Environmental pressures and restrictions influenced our diets to a great degree. But there again, that resulted in evolutionary changes and adaptations that you take into account when trying to decide the best type of modern food intake. For example, fructose in the form of naturally bound fruit is a tolerable source of sugar since it was naturally limited in quantity in the wild. But when you remove the fiber from fruit and extract all the sugar into "juice drinks" you end up with so much fructose as to have negative impacts on health. So blindly taking the "some fruit sugar is ok, thus MORE must be better" approach is wrong. But what is does tell is that a more tolerable way to consume fructose is when it's in naturally occurring fruits.
To me the critical issue is not if humans evolved to eat meat - It's pretty obvious we did - it's a question of how much, what kind, how is it prepared, and how does it fit into the overall diet that matters. That's where the tough questions lie, since something like MTOR expression might hurt maximum longevity, but have no meaningful impact until middle age or beyond. There is no conceivable downside, as far as I can see, why including occasional/limited grass-fed beef in your diet would have any negative impacts. Low quality, hormone-laden grain-fed meat is another matter.
Only if someone consumed and ALL meat or NO-meat diet, THEN they would need to pay closer attention to getting the full spectrum of nutrients. Innuits on an all-meat diet didn't just eat muscle, they ate key organs as well. Similarly, vegans need play close attention to adequate B12, dietary fats etc. As far as I know, a pure vegan diet cannot get enough B12 for maximum health, but could easily manage it through supplements.
So it's up to you, if you want to avoid meat, don't kid yourself that it's because we "aren't designed" to eat it or it's unhealthy in moderation. If you don't like the taste, or think it's unethical, then no big deal.
Edited by hypnotoad, 19 September 2010 - 04:52 PM.