Todd Moddy writes:

>For example, if a new food causes people to be somewhat sicker,
>without killing or incapacitating them outright, does it provide
>selection pressure toward adaptation?  Yes, it does, since sick
>people are less attractive as mates.  On the other hand, if that
>new food is plentiful enough to allow for population expansion,
>the population that consumes it, though sicker than the
>population that does not, will dominate in the gene pool.

I am just a lurker these days, and really don't have time to get into
post/counter-posts here, but thought I would offer the following. I think
it needs to be remembered that the above true with regard to what happens
in the _short-term_. However, in the long-term, more fit individuals (in
terms of health) will in fact eventually come to predominate once again.
For example, right now at this point in expansion of the human population,
humans have been proliferating all over the globe for the last 10,000 years
due to the exploitation of grains, dairy, etc., even at the same time these
have caused human health to deteriorate somewhat. On the other hand,
limited subpopulations have shown some small degree of adaptation already
(adult lactose tolerance; others have genes that enable greater consumption
of carbohydrates without precipitating hyperinsulinism, etc.).

Right now the human population globally is in a short-term state of
evolutionary discordance with respect to individual health, which the
differential reproductive advantages that flow from grain-cultivation/
grain-eating are temporarily outweighing. This has adversely impacted
health even as the population has successfully expanded, but the situation
will not stay that way indefinitely. 10,000 years is only a temporary blip
in the long-term.

>Furthermore, if you accept the neodarwinian assumption that
>adaptation is driven by random mutations, then there are no
>guarantees that adaptation will happen, no matter how long people
>are exposed to a given food.  This is especially an issue if
>adaptation requires multiple simultaneous mutations (i.e., if 3
>mutations are required to have no problems with a certain food,
>but individually those mutations confer no advantage).  This
>implies that the mere fact that people have been eating a certain
>food for a very long time does not imply that it doesn't make
>them sick; it only means that it hasn't killed them off.

Theoretically this might be a remote possibility. However, the above
assumes that there will be only one possible particular mutation or set of
mutations that could ever confer adaptation to a particular selection
pressure. But in the messy world of evolutionary events, there can be and
are different potential evolutionary/genetic solutions to a given selection
pressure. (Good example: most carnivores/omnivores have dental equipment
for shearing meats, etc. Humans use tools/higher intelligence
instead--something that came out of left field almost.)

Also, I am under the impression that examples of evolutionary events that
require 2 or more simultaneous mutations are not considered by evolutionary
biologists any more to be a reflection of how evolutionary events really
occur (at least not typically). For example, a big point of contention
between creationists and evolutionary biologists used to be (and for
creationists, probably still is) the split over whether the wing or the eye
could have evolved in successive stages. It seemed to creationists that it
would have required so many simultaneous interdependent mutations to have
occurred that it was an impossibility for random mutation to have produced
them. Now, however, we know that there are very plausible stepwise
sequences that could easily have produced the eye, for instance, and that
have been demonstrated by mimicking random mutational events in computer
simulations. (I believe the eye has evolved over 40 different times
separately in different branches of the evolutionary tree; and squid eyes
for instance, are not designed the same way--did not evolve the same
way--as human eyes.)

Again here, too, there is the short-term vs. long-term question.
Eventually, the sheer mathematics of probability that govern random events
such as mutations make the odds so high that at least _one_ kind of
mutation/solution will occur--and which confers at least some small degree
of relatively better fitness (and again, it has to be emphasized: not
necessarily the lone genetic solution we would predict, expect, or imagine
ahead of time)--that the above situation does not happen. That is, if one
is looking beyond short-term time horizons.

That is really the underlying issue here, or one of two. That and the fact
that evolutionary processes can/will/do come up with numerous different
genetic solutions to a given selection pressure.

Bernard Lischer writes:

> On another note, has anyone ever heard the notion put forth that an
> explanation for the good health of the Chineese, in the face of a
> carb. dense diet, might be lack of dairy (rather than the usual
> conclusion of low fat/ protein)?

I just received the book "Charles Hunt's Diet Evolution" from Amazon
yesterday. He quotes Michael Eades on the question (p. 53) as saying:

     Look at the three ways that keep [insulin] down. The main thing
     is restricting carbohydrate in the diet. You can also keep
     insulin down by exercise, or a low-calorie diet in general. The
     majority of rural Chinese work very hard and eat a low-calorie
     diet. Even though there's more rice in their diet, they still
     keep their insulin down because they work so hard and don't eat
     that much.

--Ward Nicholson <[log in to unmask]>