There are many challenging aspects to explaining human evolution including the origin of anomalous features such as the large brain, diving reflex, bipedalism, relative hairlessness, subcutaneous fat (especially in neonates) and development of speech. The shore-based hypothesis views at least two of these features (neonatal subcutaneous fat, large brain) as being dependent on nutrition. Animals including primates do not develop these features on terrestrial diets but do on shore-based or aquatic diets. A fully aquatic habitat would not be necessary to derive the benefits of the shore-based food supply. However, positioned as it is between the two extremes of fully terrestrial or fully aquatic evolution, a shore-based existence would permit humans to evolve in near constant contact with water or quite remote from it. It would support the development of bipedalism (through enhanced buoyancy, especially in infants) and could plausibly promote hairlessness and development of speech. The shore-based hypothesis only attempts to explain human brain evolution and, in parallel, neonatal fat stores. In so doing, it accounts for the known and ongoing vulnerability of the human brain and neonatal fat stores to undernutrition. Competing hypotheses need to explicitly address these important physiological and metabolic limitations or explain clearly why they are not relevant; otherwise, they are untenable. (02/24/02)
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