Páginas: 15 (3703 palabras) Publicado: 5 de abril de 2011
The Primate Baseline
With regard to diet what students of human evolution and advocates of evolutionary medicine need most from paleoprimatologists is an estimate of the nutritional pattern likely to have characterized the last common ancestor of apes and humans, a hypothetical species thought to have existed in Africa between seven and five million years ago.
If members of this elusive taxonwere like current chimpanzees and bonobos, plant foods such as fruits, leaves, gums, and stalks probably comprised at least 95% of their dietary intake with insects, eggs, and small animals making up the remainder (Milton, 1993; Tutin & Fernandez, 1993). The general nutritional parameters of an eating pattern along these lines can be estimated with modest confidence, although certainly not withmathematical exactitude. Protein would have contributed a greater proportion of total energy than it does for most contemporary humans, but with much more from vegetable sources than from animal. (Popovich, 1997) Simple carbohydrate intake would have been strikingly below that now common, and, somewhat counterintuitively, such diets would have provided only moderate levels of starch and other complexcarbohydrates so that the total carbohydrate contribution to dietary energy would have been less, not more, than is typical in contemporary affluent nations. Dietary fiber would have exceeded current levels by an order of magnitude: 200 grams vs. 20 grams a day (Milton, 1993): for some ancestral hominoids, colonic fiber fermentation may have provided over 50% of total dietary energy. (Popovich,1997) Daily intake of vitamins and minerals is likely to have been considerably greater than at present with the likely exception of iodine, consumption of which would have varied with geographic location according to oceanic proximity, volcanic activity, prevailing winds and rainfall. As it is for all other free-living terrestrial mammals, sodium intake would have been only a fraction of thatcurrently common and would have been substantially less than that of potassium. (Denton, 1995) Availability of phytochemicals, like that of vitamins and most minerals would, in all likelihood, have been substantially greater than for Americans and other Westerners.
Total fat intake, especially of serum-cholesterol-raising saturated and trans fatty acids, must have been greatly below current Americanand European levels; cholesterol intake would have been minimal. Within the polyunsaturated fatty acid [PUFA] category, partition between the omega 6 and omega 3 (w-6 and w-3) families would have been reasonably equal or skewed slightly towards the w-3s. Polyunsaturated fatty acids from plant sources are predominantly, if not exclusively, 18-carbon or less in chain length; linoleic acid (LA,C18:2, w-6) and a-linolenic acid (ALA, C18:3, w-3) are typical. Accordingly, dietary intake of the longer chain C20 and C22 PUFAs such as arachidonic acid (AA, C20:4, w-6) and docosahexaenoic acid (DHA, C22:6, w-3) would have been low. (Eaton, 1998)

Scavenging, Hunting and Brain Expansion
Paleodental evidence suggests that after the divergence of early hominids from the hominoid ancestral line, agradual increase in consumption of harder and/or more abrasive foods occurred - most likely nuts and seeds. This change probably increased intake of vegetable fat (mostly non-serum-cholesterol raising in nature) and would, perhaps, have facilitated overall access to food energy, but probably had little other nutritional effect. About 2.5 million years ago, however, there is evidence that animalfoods began to occupy an increasingly prominent place in our ancestor�s subsistence. Decreased molar size, less mandibular and cranial robusticity, and alterations in incisor shape all suggest greater emphasis on foods requiring less grinding and more tearing, such as meat.
An increasing proportion of meat in the diet would obviously have provided more animal protein, a factor perhaps related to...
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