... The combination of hairlessness and subcutaneous fat seems almost totally confined to aquatic mammals and humans. Two other characteristics are covered in some depth in this article: The discovery that some prehistoric shell middens consist of deep-water shellfish, which must be the result of breath-held diving. This human skill, again unique among primates, is obviously quite ancient. Furthermore, recent experiments suggest that in humans, in addition to seals and ducks, vascular constriction is not limited to the arterioles but extends to the larger arteries, too. This indicates some degree of specialized adaptation to a diving life. Most animals with a sodium deficiency display an active craving for salt which, when satisfied, disappears. In humans, salt intake has little or no relation to the body's needs. Some Inuit tribes avoid salt almost completely, while people in the Western world consume 1520 times the amount needed for health. In other works, a single African species (assuming humans have an African origin) possesses a wildly different scheme of salt management. Humans are also the only primates to regulate body temperature by sweat-cooling, a system profligate in the use of sodium. Proponents of the Aquatic Ape Hypothesis believe that sweat-cooling could not have developed anywhere except near the sea where diets contain considerable salt, in fact much more salt than the body requires. This article also deals with certain skeletal features of early man that seem to indicate an aquatic stage. For example, the Lucy skeleton has a shoulder joint that indicates that Lucy spent a lot of time with her hands above her ...