> It is not some theoretical, unexamined
> issue that we are discussing here. Large populations of human beings
> have lived, quite healthy and long lives, on entirely vegetarian diets.
> And they have come upon their diets through an evolutionary process, but
> have no method or need to quantify and track components, today.
Ravi,
It is well-established (cf Guns, Germs, and Steel et al) that agriculture emerged around 8000 BC (slightly later in the Americas). Before then, humans did the hunter-gatherer thing. Men hunted for animals and fished, Women collected nuts, berries, roots, weeds, insects, honey, etc.
Hence, only the emergence of the agrarian lifestyle allowed for humans to adopt a more grain- and legume-oriented diet. This was a mere +/- four hundred generations ago (10000 yrs / 25 yrs). All the evidence I have ever heard of suggests that we have the same metabolism as did the hunter-gatherers. We have the same teeth (molars for crushing nuts and stuff), incisors for tearing flesh. We have the same digestive tract; halfway in length between a lion's (a carnivore) and a cow's (a ruminant).
It furthermore appears that humans generally require some form of animal-derived food to remain healthy. As Ms. Info has pointed out in this thread, certain things that we require -- B12, certain amino acids and omega fats -- aren't readily available and/or easily assimilated in vegetable form. And little Ivan -- just as everyone else at his station in life -- most definitely requires animal-derived food; in fact, that is probably his chief source of sustenance at this point, thanks to the good offices of Lisa.
That a small percentage of the population can survive and do well on strict vegan diets I don't argue. However, it is also clear that not many people are suited to it. Also, the epidemiological verdict on its viability is still out. Do vegans suffer long-term effects from lack of certain nutrients? We don't know yet. If you can point to a society which has lived and thrived as vegans for many generations, please do, as I am unaware of one. At the same time, we do know that people of at least one blood group, 'O', don't do well on vegetarian diets; they grow pale and weak. They need at least a small amount of animal protein a few times a week to flourish.
At this point, we can have the following debate: where should we get our animal-derived nutrition from? From one point of view (ethics), one could argue that one should not kill animals to acquire sustenance and rely solely on milk and eggs. From a different point of view (health), one could argue that dairy products are not suitable foods for adults; the casein is hard to digest, the calcium is not easily assimilated, the growth hormones stimulate tumors, etc., therefore we are better off eating the flesh of animals rather than their milk.
There are other considerations as well. Here is a utilitarian one: In times past, people in temperate climates kept a pig as an investment (is this where "piggy-bank" came from?); they fattened it up in the warmer months and then slaughtered it in the fall and lived off the meat to help get through the winter. Small amounts of dried pork protein and fat livened up endless dreary dishes of potatoes and turnips as well as providing certain essential nutrients. Such people may not have the option of keeping a cow around to milk.
The ethical question of whether or not to "kill animals" is just one element of a very complex equation. And sorry: I don't believe there is any evidence that evolutionary factors favors vegetarianism.
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Colin Brace
Amsterdam