Jennie Brand Miller writes:

>In her last posting, Loren wrote:
>
>'This evolutionary strategy of molecular mimicry to deter
>predation or to exploit another organism has apparently been with us for
>hundred's of millions of years and is a quite common evolutionary
>strategy for viruses and bacteria.'
>
>Wouldn't this mean that the foods that we have exploited most often for the
>longest period of time, should be the highest source of these molecules,
>not >the foods (like cereals) that we've adopted most recently?

It might if one assumed that plants were constantly evolving strategies of
molecular mimicry while the animals that preyed on the plants weren't
countering the mimicry with ever-evolving immune-system strategies of their
own. One key evolutionary characteristic of the predator/prey relationship
(in this case foraging animals vs. the plants that are their "prey") is
that it is an *arms race*--i.e., it is *ongoing*, not a situation of
evolutionary stasis that allows one side to continue developing its arsenal
while the other side simply stands still becoming a victim. (Or more
accurately, if one side cannot cope over evolutionary time and *does*
become a victim, then it goes exteinct.) Each side tends to be continually
responding to the need to evolve new survival strategies in response to
whatever "opponents" they face change what *they* do over time.

Thus, just because plants that we have been associated with for long
periods of evolutionary time could be expected to evolve
ever-more-sophisticated strategies of molecular mimicry against a
long-familiar adversary doesn't mean that we the adversary have a biology
or physiology that is just sitting there doing nothing about it. Because we
are a moving target. Our bodies, too, are continually evolving new
strategies to counter the deterrent mechanisms of the plants that counter
ours. But of course when changes are introduced suddenly (as would be the
case with grains in the human diet right now) there is something of a time
lag where "evolutionary discordance" prevails while the species is still
working out an evolutionary coping strategy.

However, so far, this way of looking at it only considers *adversarial*
evolutionary relationships. It is easy to overlook--when characterizing
plants' and animals' evolutionary strategies in regard to each other as
adversarial--that just as importantly relationships may end up being
*symbiotic* instead. For example, take the classic example of fruits.
Fruits in some sense symbiotically exploit the animals that eat them by
using them as seed dispersers (through their feces). So the relationship in
this kind of situation is advantageous to both sides.

On yet a third hand, sometimes the relationship between predator and prey
is at the same time a complex mixture of both symbiois *and* that of
adversary. For instance, carnivores that prey on herbivores may help keep
the herds thinned out which keeps them from overgrazing the landscape and
going through seasonal die-offs from overshooting the landscape's capacity
to support them. Things can get complicated.

However, one would still expect as a general rule that those foods (or
environmental conditions, or any input or stressor for that matter) that a
species has had the least exposure to would be the ones with which *mutual*
evolutionary coping strategies would not yet have been worked out (mutual
is the key word here)--whether that mutual relationship be symbiotic in
nature or adversarial, or what-have-you (however complex).

Think of the cases where species alien to another environment (starlings,
Dutch elms, etc.) have been suddenly introduced. The result is normally a
period of instability before things settle down into some sort of long-term
balance.

No matter what the selective pressures are--whether they be food,
environment, or whatever--one of the foundational assumptions of evolution
as a paradigm (and of the things that gives it part of its explanatory and
predictive power) is that *anything* significantly new in evolutionary
terms is almost inevitably going to be *discordant* with the species
adaptation; and there will necessarily be a time lag before evolutionary
selective processes have a chance to weed things out to establish more of a
balance. Even if that "balance" is a dynamically shifting one as in an arms
race, or one of symbiosis, or both.

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

P.S.--By the way, Loren Cordain is not a she--he is a he! :-)