Loren Cordain wrote:

[..]

> In regards to the out of Africa hypothesis and its relationship to
> diet I think the data supports the concept that early humans left
> Africa by at least 1 MYA or possibly earlier and were replaced by
> anatomically and behaviorally modern humans in the past 40-60,000
> years.  Anatomically modern humans likely evolved in Africa and first
> appear in the fossil record ~100-120 kYA.  Therefore this population
> in theory would represent the last common ancestor for which all
> modern humans could trace a common gene pool and ideally could serve
> as the model for the genetic nutritional requirements of all present
> day humans before the confounding influence of various environments
> wrought by migration etc. on our genome.  It is inappropriate to
> dismiss the nutritional evolutionary experience of all hominids prior
> to the split between anatomically modern humans and their
> predecessors because we share more genes with these hominids than
> those for which we differ.

[..]

> either hunted or scavenged carcasses.  This consumption of animal
> based foods which led to a relatively smaller and less metabolically
> active gut is still with us today.  So presumably all hominids
> including modern humans share the basic gastrointestinal physiology
> that evolved in response to a high meat based diet.  Further, all
> modern humans have poor ability to desaturate and chain elongate 18
> carbon lipids to 20 and 22 carbon lipids (3).  Similar to cats
> (complete carnivores) the inability to efficiently desaturate and
> chain elongate plant based 18 carbon lipids to the 20 and 22 carbon
> lipids needed for membrane and eicosanoid function has occurred
> because the selective pressure for desaturation and chain elongation
> has been relaxed.  Humans like cats eat higher up on the food chain
> (ie. other animals) in which 20 and 22 carbon lipids are present thus
> there is little need to retain genes for lipid desaturation and chain
> elongation of plant based 18 carbon lipids.  Similar arguments can be
> made for the synthesis of taurine (a conditionally essential amino
> acid) and the conversion of beta carotene to vitamin A.
>
> Thus the basic physiological adaptation to a meat based diet occurred
> early on and was likely complete by the time early hominids migrated
> to northern latitudes.  Fruit eating hominids could not have left the
> environs of the tropics until they began to utilize a food source
> that was present not only in the tropics but elsewhere.  The remains

[..]

Looking back before the paleolithic era at our evolutionary roots:

One physical anthropologist claims that the predecessors of the first
primates were insectivores and that the whole of the primate
evolution has been influenced by that gastric formation.  I assume
that these insectivores were rather similar to cats in many ways and
may have had a common ancestor with cats a few million years before
ie: maybe 20-50mya.  But we see that some primates are essentially
herbivorous eg: Gorilla gorilla, various Australopithecines (by
dentition) eg: A. boisei.  Perhaps some species have adapted at least
partially to a more herbivorous diet.  There's great dentitional
difference between gorilla and Australopithecine thus more to study
on their herbivoral adaptations.

Depending on one's cladistics perhaps the robust Australopithecines
were not ancestors of various Homo ie: perhaps there's another line
of descent from the pre-primate insectivores to H. sapiens than
through Australopithecus or perhaps a branch early in the development
of Australopithecines.

source: Syracuse University lectures in physical anthropology by
Prof. Mark Fleischman spring 1997.

I'd be interested in analyses of the success of the herbivouous
Australopithecines and their apparent replacement by early Homo.  Is
this simply a result of encephalization or are there other factors
eg: social adaptations, climatic and other environmental changes etc?

Both Dr. Cordain's scheme and the descent from insectivorous
ancestors lead me to suspect the high protein and fat intake we
associate with paleo diet might be most appropriate for most modern
humans; something our physical nature requires or is best adapted
for.

Dick
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