Note: I had to split this into two parts since as a single post the
listserver rejected it for exceeding the line limit. --Ward
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I primarily lurk on this list, so I don't have time to get involved in any
extended discussions (this posting is long enough by itself), but if I may
interject something here in Todd's and Amadeus' debate.
Amadeus, it seems to me that in your reasoning you are attempting to have
your cake and eat it too with evolution. On the one hand you acknowledge
that evolution towards a diet with greater levels of meat has taken place
in the last 2.5 million years of human evolution. Yet at the same time you
insist that the higher levels of meat are not something humans are any more
in need of, or can make better use of, than the diets of pre-hominids or
the very earliest pre-humans (Australopithecus, etc.) with lesser levels of
meat in their diet. At the very least, you seem to be saying that humans
can make just about as good use of the nutrients in plants as if they were
to get them from meat, so that the amount of meat in one's diet doesn't
really matter very much.
But evolution either happens or it doesn't. And when it does, there are
consequences that can't simply be brushed aside or ignored out of
existence. To acknowledge that humans evolved to where they were handling
more meat in their diets, but then to turn right around and say it doesn't
make any difference is a flat logical contradiction where evolution is
concerned. Evolution is driven by just such differences.
What is being ignored in the assumptions you are making is that when a new
trait evolves (adaptation toward higher levels of meat in the diet in this
case), it generally occurs at the expense of something else. Evolution is a
compromise among competing selective pressures. To some extent it's a
zero-sum game, where an advantage in one department comes at the expense of
a certain amount of disadaptation in another.
One very clear example of this is that as hominids became bipedal and
better adapted for locomotion on the ground, they became less well-adapted
for life in the trees. The same reasoning applies with the continuum of
adaptation between plant and animal foods. You wouldn't argue that humans
are as good tree-climbers as apes, but you are attempting to use the same
line of reasoning in saying they can be much closer to vegetarianism in
their omnivorousness as profitably as can apes. Now of course, humans are
omnivores, so we do have adaptations for eating both animal AND plant
foods, but the degree of adaptation to one or the other, and their relative
efficiencies will depend on the proportions of each that prevailed in the
diet over evolutionary time, particularly more recent evolutionary time.
What matters where evolution is concerned is what a species is *most
recently* well-adapted to. It is a "red herring" to focus too myopically on
how long something has been going on in evolutionary history. For purposes
of humanity's optimum diet, it doesn't matter as much what the creatures in
our lineage ate 4 Mya or even 2 Mya. What weighs a lot more heavily is what
we ate in the most recent evolutionary time period that was relatively
stable enough in terms of our food consumption patterns for that to have
been well-adapted to. To suggest that humans are more well-adapted to the
diet eaten by our progenitors 4 Mya than the diet we ate, say, 1 Mya, is
simply not reasonable--not if you are looking to evolutionary reasoning for
support, that is. (Which is what this debate is basically about, is it
not?) Especially not when the human diet changed considerably from that of
its ancestors during that time, as Todd has emphatically pointed out
previously.
When we consider that the human genus (Homo) saw its inception with Homo
habilis about 2.5 Mya, then evolved through Homo erectus (1.7 Mya), and
then through an intervening transitional stage of Archaic homo to modern
humans (Homo sapiens) about 90,000-150,000 years ago, certainly it doesn't
make any sense to go any further back than but a single species change at
the most (a species change by definition representing a new set of
adaptations). Going back to Homo erectus who existed from perhaps 1.7 Mya
to 300,000-400,000 y.a. in trying to get a handle on what humans are fully
adapted to is stretching it the most it could plausibly be stretched, and
even that is probably stretching it a bit. And Homo erectus is thought to
have had a diet with substantial amounts of meat.
But in going back to ape-like pre-human hominids, you are going back beyond
2.5 Mya in terms of inception dates for these species--to 4.5 Mya in the
case of the first known (non-human) hominid (Ardipithecus ramidus)--to
creatures about 3 or 4 species changes prior to our own. We have heard this
line of defense so many times before from numerous people in the
raw-vegan-fruitarian camp who want to support their diet with evolution
that it is getting to be a caricature of itself by now: "Why, to back up
our belief in evolutionary support for fruitarianism in humans, we'll just
go back to the APES!" :-)
I say: If one thinks near-fruitarianism, or near-veganism, or even a mostly
vegetarian "omnivorous" diet is the optimal evolutionary diet, then be my
guest and become an ape or pre-human Australopithecus for whom these *were*
optimal. But one cannot logically say these diets are reasonably optimal
diets for humans if the intent is to use evolutionary reasoning for
support. You can only support them as the optimal diets for the creatures
there is actually evidence for having eaten those diets, and the evidence
does not support the genus Homo (since Homo habilis 2.5 Mya) ever having
eaten a diet with those minimal levels of animals in it.
(continued...)
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