Hi,
a quick response to Barry repeating a number of points that I made on the
list a few months ago.
> On teeth, the article makes out that our teeth are designed to cope with
> plant foods. I defy anyone to clench their teeth together and then move
> their jaws sideways to "grind" in the way that herbivores do.
Herbivores that grind their plant foods with their teeth in that sideways
motion are usually folivores, that is they eat leaves with a high
cellulose and often silica content. There are many foods of plant origin
that do not require grinding to be palatable, ie fruits, tubers, shoots.
Not all herbivores need grinding teeth, ie a number of primates.
> If we take this one step further and compare our colons with those of our
> nearest relatives we find that our colon/caecum accounts for around 20% of
> our gut's total volume, whereas the colons of the fermentative chimps and
> gorillas is more than 50% of the total volume.
Yes, but as I have said before, primates that eat 'high quality' energy
dense plant foods have similar gut and colon/caecum proportions to us, eg
baboons and capuchin monkeys. Not all primates/chimps/apes are fermenters.
> Our gut is a simple tube with a bulge (stomach) at its beginning -- exactly
> the same as all carnivores. Its total length is approximately 5 times body
> length. That of the big cats is approximately 7 times body length. The gut
> of a herbivore, by contrast is some 27 times body length and, in the
> ruminants, much more complex. In our nearest relatives, it is also a similar
> length and, as I have already mentioned, it differs markedly in that apes'
> colons are much bigger than ours.
>
> In other words, our gut, in terms of length and complexity is even more
> "carnivore" than the big cats.
The 'simple tube' is not an accurate description of the human gut. The
proportions for humans are approx: 20% stomach, 60-65% small intestine,
1-3% caecum, 20-ish% colon, very different to carnivores (to be specific
the order Carnivora) in the small intestine part.
But not all herbivores have similar gut proportions. Some have aspects of
their guts similar to carnivores (eg no caecum), yet are definite
herbivores - eg hippos. I feel Barry is being rather simplistic in his
division of gut type and correlation with dietary group. We are not
more similar to carnivores than we are to herbivores, for the reason that
there is a lot of variation throughout the mammalian kingdom.
For an excellent discussion of this whole subject, complete
with very comprehensive and comprehensible diagrams, see
Stevens, C. E. and I. D. Hume (1995). Comparative physiology of the
vertebrate digestive system. Cambridge, Cambridge University Press.
I hesitate to say this, as I do not want to be offensive, but I venture
that Barry would rather that this simple division of carnivore/herbivore
does hold up, as it appears from his prior postings that he would rather
that we as humans are incontrovertibly carnivore. I have no problem with
this attitude towards human diet, unless the individual holding it twists
the science to suit their opinion.
Tamsin
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Dr Tamsin O'Connell
Research Laboratory for Archaeology
University of Oxford
6 Keble Road, Oxford, OX1 3QJ, UK
tel:01865-283641
fax:01865-273932
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