Doug Schwartz writes:
>I'm not trying to say that humans did not evolve in a meat-eating
>mode (I think you have pretty much demolished the "Garden of Eden"
>scenario). But I have a couple of questions:
>What about our dentition, why is it that we have the teeth of
>herbivores?
Doug, your question seems to imply that teeth can only be classified by
mutually exclusive categories in either/or fashion. Evolutionary scientists
rarely use classification terms like "herbivore," "frugivore," "carnivore,"
etc., in any exclusivist sense--they are a simply a convenient aid to
indicate *broad* dietary trends, but there are few "pure" diets in nature.
At least not in the realm of primate feeding, I can tell you that. My
understanding of the evolutionary data is that while hominid teeth share
characteristics with herbivores, frugivores, etc., they are also adaptable
to other foods as well. But the real key to all this is in your next
question:
>Does this imply that meat was intended to only play a
>very subordinate role in the diet, and/or that tool usage took over
>this role from canine teeth?
Yes to some degree to both of the above. The evolutionary picture is that
hominid teeth size and robustness have indeed decreased over evolutionary
time, and the strong likelihood is that this was indeed because the use of
tools reduced the need for extra-robust teeth. In fact, there is a very
interesting debate in paleontology right now whether homo habilis evolved
from the "robust" or "gracile" australopithecines, but in any event,
beginning with homo habilis--the first substantial tool-user
documented--the human line of descent has become more "gracile" in build
over time, right down to the present time.
How "subordinate" the meat intake was, however, is relative to one's idea
of what is "a lot" of meat. The Eaton research team, based on extensive
surveys of recent hunter-gatherer tribes, and assuming somewhat similar
foraging patterns for our ancestors, has arrived at an estimate of 65%
plant/ 35% flesh in late Paleolithic times, although it probably varied
greatly depending on the specific habitat. That's twice as much plant food
as meat, but a vegetarian would undoubtedly still consider that "a lot."
Even 10% or 20% would probably be considered "a lot" from that perspective.
>Granted that humans (& certainly other primates such as chimps)
>evolved eating meat. Does this necessarily mean that meat is
>necessary or even desirable?
If you accept evolution at all, then yes. The very definition of evolution
is that genetic adaptation falls in line with whatever behavior and
environment persist over the course of many generations. Those of one
generation who survive to pass on their genes to the next will more likely
be those individuals whose genes are most fit for the environment and
behavior that was engaged in. Thus over time, if the behavior and
environment persist from one generation to the next to the next to the next
(etc.), evolution ensures an increasingly close fit between genetic
adaptation and behavior. Within X number of generations, only those whose
genes are conducive to survival within the framework of the environment and
behavior that persist will remain as descendants.
This brings up the prevalent idea that gets bandied about a lot within
idealist-diet circles that any deviation from some "original" state of
evolutionary adaptation means an decrease in evoluitionary fitness the
further we get from our "real" or "true" adaptation "way back when." But
such ideas show a gross lack of comprehension as to how evolution works.
There *are* no original states of adaptation (unless you want to go all the
back to the first bacteria that sprung from the muck)--it's all relative.
Homo sapiens (modern humans) evolved from homo erectus evolved from homo
habilis, from australopithecines, and themselves from some primate ancestor
shared in common with the line of the descent that split off not only into
hominids but chimps and gorillas as well. Take it further back, and you are
looking at the apes of Miocene times (30 millions years ago? I forget
exactly), and before that the very first primates of 60-70 million years
ago.
To repeat: If you accept that evolution happens at all, then there is no
way around the fact that changes in behavior (often due to changes in
environment) are themselves what lead to new genetic adaptations and new
species. That this happens and is the mechanism for the origins of new
adaptations and new species is the very definition of evolution itself.
>I think it would be very, very
>interesting to take primarily carnivorous animals (such as cats or
>dogs) and raise them on an entirely vegetarian (preferably raw) diet
>to see what happens. I believe that many dogs are essentially
>vegetarians anyway (albeit grain-eaters) from their dog food.
I find this hard to believe given that dogs evolved from wolves and were
tamed only in roughly the last 10,000 years or so. Is this your own
speculuation, or can you present some science on this we could go look up?
>Sure humans can eat meat, but I would be very surprised if eventually
>their aging rate is accelerated & diseases such as cancer show a
>greater & earlier incidence.
I would like to see some peer-reviewed substantiation of this speculation.
The closest I know of is T. Colin Campbell's China Study which apparently
shows increases in cancer when meat represents over 5-7% of the diet.
However, studies of hunter-gatherers eating diets approximating what is
thought to be the Paleolithic norm with substantially more flesh than that
have shown very few signs of degenerative diseases. In fact they are among
the healthiest peoples known. I am not sure cancer was specifically a
subject of these studies because at the time many of these studies were
done, cancer was not the pandemic it is now. But at the time the studies
were done, rates of other degenerative diseases of concern such as
diabetes, heart disease, etc., were extremely low. Unfortunately these
kinds of studies are probably no longer possible to re-do and ask new
questions, since there are almost no tribes left now who have not been
assimilated into modern cultures, or whose lifestyles have not seen drastic
changes since "contact" with the "modern urban omnivore/ vegan/instincto."
:-)
--Ward Nicholson <[log in to unmask]> Wichita, KS
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