Hello, Arjen ~

In general, I like your thinking, but some points confuse me.  A few
johnny-come-lately comments...

> However, there is a way that
> eating junk food can become established in humans when
> we keep in mind that natural selection doesn't lead to
> optimum health but to maximum reproduction. In that
> case the negative health consequences of junk foods
> don't matter, since somehow it enhances the
> reproductive success of the junk food eater. This
> seems to be the exact situation: we all can observe
> that junk food eaters breed more than health conscious
> people, whatever the reason might be. So this can lead
> to a trait becoming established in humans, while it
> actually has negative health consequences!! This is
> extremely important, because the same situation might
> apply to cooked foods!!

The likelihood that the growing incidence of junk food eating is the result
of the high birth rate among junk food eaters seems to me to be rather slim.
I think the spread is much too rapid.  It's more like the spread of a
religion or a drug.  Plenty of people get born into junk food eating
families, for sure.  But I think that many more are converted.  Certain
tastes (like certain ideas) have a wide appeal regardless of how healthful
(or sensible) they are.  Even folks who were fed decent food as youngsters
will often leap at the chance to eat delicious crap day in and day out.

> Originally human ancestors
> evolved in the tropics and had a mainly frugivorous
> diet, probably including greens and possibly some
> invertebrates. They also developed a huge brain
> capacity

Why, I wonder.  And why haven't lots of other animals also evolved huge
brain capacities?  Was a bigger brain advantageous for our ancestors but not
for other creatures?  Or do different species have widely differing rates of
mutation?  I don't see how plain ol' natural selection puts all these pieces
together.

The idea of evolution is, to me, very much like that old paradox about
Zeno's arrow (was it Zeno?).  The arrow has to get halfway to the target
before it gets to the target.. but it has to get halfway to halfway first..
and halfway to THERE first.. Since one can chop the distance in half an
infinite number of times, the arrow should never get to the target!
Evolution is rather like that in that it gets very problematic when you zero
in on the small scale.

Say you've got a band of medium-brained human ancestors.  They have some
variation in brain size, but none of them has a brain as large as their
descendants will have.  So, at some point, in order to add this new size to
the mix, you have to have a mutation.  **Something which isn't there cannot
be selected for.**  So you have to have this larger brain show up as a
mutation in order to add it to the gene pool, don't you?  And a larger brain
in full working order probably requires not just one, but several mutated
genes.  How often does an advantageous mutation occur?

If an advantageous mutation happens as often as once in every 100,000
individuals (very unlikely, I think), how does one individual end up with
the whole mutation cluster needed for these bigger, better brains?  (And
would only one of those required mutations survive on its own to await the
arrival of others, or do they all have to happen together?)  And then how
does this new brain spread far and wide?  From that one individual?  It
seems to me that it would be mighty difficult.  Even if you could get that
one unlikely individual, he or she would have to have to have an awfully
large number of offspring, wouldn't it?  So you've got the unlikeliness of
just the right group of mutations getting together in the first place
coupled with the odds of that mutation cluster being passed on to enough
offspring to make it common enough to be the object of future selection
pressures.  Just looks mighty tough to me...

> It is
> interesting to notice that Chimps and Gorillas have
> extended canines, even though the amount of meat they
> eat is minimal. This implies that even the smallest
> amount of meat eating requires extended canines.

That's a big leap, isn't it?  Anatomical features can become specialized for
purposes that are quite different from those for which they originally came
about, as you mentioned yourself with the antler example.  Other examples
would be outrageous display feathers in some birds or worm-mimicking tongues
in some fish.  Who is to say that these canine teeth have to maintain their
dietary usefulness at all?  Couldn't they be simply display teeth?

> The argument that humans are only scavengers is not very
> convincing either, because even then you expect them
> to have extended canines, since it makes it a lot
> easier to rip open carcasses (especially before we
> started using tools).

But one of the reasons for being a scavenger and not a killer is precisely
because someone has opened up the carcass for you!  I doubt that most of the
animals scavengers feed on just dropped and died intact.  Most probably had
help from someone with sharp teeth and/or claws.

> I also would like to point out that
> eating of animal products, especially when raw, have
> nowadays serious risks involved, like Mad Cow's
> Disease,

The mainstream theory on Mad Cow says that cooking is no defense, that
prions can remain infective even after autoclaving.  I'm not sure what the
Purdey answer to the question of cooking would be.  (The Purdey theory of
Mad Cow, the one mentioned by Anwar, is about how rogue prions are created.
I don't know if it addresses how to eliminate them.)

Fun stuff, Arjen!  Thanks for spicing things up around here. :)

Carol