Dean Esmay wrote:

> A review of modern hunter/gatherer diets(1) shows tremendous variation in
> diet based on these factors and I don't see how it's possible to argue that
> it has not always been so.  In fact I think it can easily be argued that
> one of man's primary evolutionary advantages has been the ability to adapt
> to an extremely wide array of foods.

I'm not sure if we have been over this ground already, but it is
perfectly possible to argue (and biologically it must be the null
assumption) that the vast majority of our nutritional requirements have
(in the evolutionary past) been satisfied by a relatively small number
of food items.

Optimal foraging theory suggests that when all food types are ranked in
terms of the time costs of processing them and nutritional benefits
resulting that a foraging indicidual can then be thought of as making a
choice when it encounters a potential food item, along these lines.
Should I stop and eat this item or would my time be better spent
continuing my search for a more rewarding item. Stop and eat now will be
common if the processing time is very small or the density of better
options is (or is likely) to be low. Leaving potential food items will
be common where processing times (including time taken to catch, dig-up,
clean and eat etc..) are high or the probablity of something better
coming along soon is also high.

Following this simpel algorithim thorugh suggests that species will tend
to minimize the number of food species to that most efficient set. This
is most likely to leave food resources for growth and reproduction after
maintainence. The assumption here is that the foragers is limited by a
macronutrient. Micro-nutrient limitation might complicate things.

Modern hunter-gatherers tend to live in environments where the costs of
moving on to the next potential resource are relatively high (!Kung
women appear to have reached the point where foraging distance has
compromised their reproductive physiology), they take many sub-optimal
items in their diet because the density of optimal items is low and
search costs are high, leading to dietary diversity. When there is a
rich and cheap source of food they concentrate on that (Mongogo nuts).

Our pre-agricultural ancestors in general did not live in the areas
currently occupied by hunter-gatherers. Because they occupied areas with
richer resources now overun by agro/pastoralists the dynamic between
food choice and foraging time would be different. Less food species
would be included in the diet as the density of higher quality items
increased. Therefore I would argue that dietary diversity amongst modern
HG's is derived and is not good evidence for the basic evolutionary
dietary strategy adopted by humans in the late Pleistocene.

If dietary diversity is a basic human adaptation then we have to
conceive of humans as living largely in an impoverished and marginal
environment with few or no 'keystone' resource species (such as figs)
providing resource refugia during seasonal resource restrictions. Why
would humans live in these places and where are they?

All this mainly applies to the female diet, males will on the whole do
more risky things, but then their reproductive sucesss is not so closely
linked to nutritional status as females. I am not arguing for an all
meat diet for these women, but I suggest that the basal dietary strategy
may have been based on the efficient exploitation of a few species at
any one time and place. These key species would clearly vary accross
space and through time but then that kind of diversity is not what we
are talking about when we look at modern hunter-gatherers.

Well there you go, I'm an unreconstructed evolutionary ecologist so what
would I know?