Williams Marcel F
Mu Omega Enterprises, 748 Oakland Avenue #306, Oakland, CA 94611, United States.
Med Hypotheses. 2006;66(2):247-57. doi: 10.1016/j.mehy.2005.09.024. Epub 2005 Nov 2.
Amongst primates, kidneys normally exhibiting lobulated, multipyramidal, medullas is a unique attribute of the human species. Although, kidneys naturally multipyramidal in their medullary morphology are rare in terrestrial mammals, kidneys with lobulated medullas do occur in: elephants, bears, rhinoceroses, bison, cattle, pigs, and the okapi. However, kidneys characterized with multipyramidal medullas are common in aquatic mammals and are nearly universal in marine mammals. To avoid the deleterious effects of saline water dehydration, marine mammals have adaptively thickened the medullas of their kidneys--which enhances their ability to concentrate excretory salts in the urine. However, the lobulation of the kidney's medullary region in marine mammals appears to be an adaptation to expand the surface area between the medulla and the enveloping outer cortex in order to increase the volume of marine dietary induced hypertonic plasma that can be immediately processed for the excretion of excess salts and nitrogenous waste. A phylogenetic review of freshwater aquatic mammals suggest that most, if not all, nonmarine aquatic mammals inherited the medullary pyramids of their kidneys from ancestors who originally inhabited, or frequented, marine environments. So this suggest that most, if not all, aquatic mammals exhibiting kidneys with lobulated medullas are either marine adapted--or are descended from marine antecedents. Additionally, a phylogenetic review of nonhuman terrestrial mammals possessing kidneys with multipyramidal medullas suggest that bears, elephants and possibly rhinoceroses, also, inherited their lobulated medullas from semiaquatic marine ancestors. The fact that several terrestrial mammalian species of semiaquatic marine ancestry exhibit kidneys with multipyramidal medullas, may suggest that humans could have, also, inherited the lobulated medullas of their kidneys from coastal marine ancestors. And a specialized marine diet in ancient human ancestry could, also, explain the reactivation and enumeration of corporeal eccrine sweat glands and the copious secretion of salt tears. The substantial loss of genetic variation in humans relative to other hominoid primates, combined with the apparent isolation of early Pliocene human ancestors from particular retroviruses that infected all other African primate species, may suggest that such a semiaquatic marine phase, during the emergence of Homo, may have occurred on an island off the coast of Africa during the early Pliocene.
在灵长类动物中，肾脏通常呈现分叶状、多锥体的髓质，这是人类独有的特征。虽然在陆生哺乳动物中，髓质形态自然为多锥体的肾脏很少见，但具有分叶状髓质的肾脏确实存在于以下动物中：大象、熊、犀牛、野牛、牛、猪和霍加狓。然而，具有多锥体髓质特征的肾脏在水生哺乳动物中很常见，在海洋哺乳动物中几乎是普遍存在的。为了避免海水脱水的有害影响，海洋哺乳动物适应性地增厚了它们肾脏的髓质，这增强了它们在尿液中浓缩排泄盐分的能力。然而，海洋哺乳动物肾脏髓质区域的分叶现象似乎是一种适应性变化，目的是扩大髓质与包裹在外的皮质之间的表面积，以便增加因海洋饮食导致的高渗血浆的量，这些血浆可以立即被处理以排泄多余的盐分和含氮废物。对淡水水生哺乳动物的系统发育研究表明，大多数（如果不是全部的话）非海洋水生哺乳动物的肾脏髓质锥体是从最初栖息或经常出没于海洋环境的祖先那里继承来的。所以这表明，大多数（如果不是全部的话）具有分叶状髓质肾脏的水生哺乳动物要么适应了海洋环境，要么是海洋祖先的后代。此外，对具有多锥体髓质肾脏的非人类陆生哺乳动物的系统发育研究表明，熊、大象以及可能还有犀牛，也从半水生海洋祖先那里继承了它们的分叶状髓质。一些具有半水生海洋祖先的陆生哺乳动物物种呈现出多锥体髓质的肾脏，这一事实可能表明人类也可能从沿海海洋祖先那里继承了肾脏的分叶状髓质。古代人类祖先的特殊海洋饮食也可以解释身体外分泌汗腺的重新激活和数量增加以及大量分泌含盐眼泪的现象。与其他类人猿灵长类动物相比，人类遗传变异的大量减少，再加上上新世早期人类祖先明显与感染了所有其他非洲灵长类物种的特定逆转录病毒隔离，这可能表明在人类出现的过程中，这样一个半水生海洋阶段可能发生在上新世早期非洲海岸外的一个岛屿上。
