Oftedal Olav T
Smithsonian Environmental Research Center, Edgewater, Maryland, USA,
Nestle Nutr Inst Workshop Ser. 2020;94:1-10. doi: 10.1159/000505577. Epub 2020 Mar 10.
Lactation is a defining characteristic of all mammals, and, indeed, mammals draw their name from mammae, or mammary glands. The evolution of mammary glands has been the subject of debate since Charles Darwin. The purpose of this brief review is not to examine all past theories of mammary evolution but to consider the evolution of the mammary gland in relation to (1) modern paleobiology, giving special attention to the mammaliaforms which had many mammalian features, including delayed tooth development suggestive of milk intake. (2) Comparative aspects of mammary development in monotremes, marsupials, and eutherians, which reveal the close developmental relation of mammary glands to other skin glands and hair follicles. (3) The evolution of caseins, which are now known to derive from secretory calcium-binding phosphoproteins, which have a long history in regulating biomineralization. (4) The evolution of lipid secretion, and especially the evolutionary incorporation of immune system components (such as xanthine oxidoreductase) into the fat globule membrane. (5) The evolution of lactose synthesis, and especially the synthesis of the wide array of oligosaccharides found in some milks, including monotremes, marsupials, caniform carnivores, and humans.
哺乳是所有哺乳动物的一个决定性特征，事实上，哺乳动物的名字就来源于乳腺。自查尔斯·达尔文以来，乳腺的进化一直是一个有争议的话题。这篇简短综述的目的不是审视过去所有关于乳腺进化的理论，而是探讨乳腺的进化与以下方面的关系：（1）现代古生物学，特别关注具有许多哺乳动物特征的哺乳形动物，包括提示有乳汁摄入的延迟牙齿发育。（2）单孔目动物、有袋类动物和真兽类动物乳腺发育的比较方面，这揭示了乳腺与其他皮肤腺体和毛囊之间密切的发育关系。（3）酪蛋白的进化，现在已知酪蛋白源自分泌性钙结合磷蛋白，这类蛋白在调节生物矿化方面有着悠久的历史。（4）脂质分泌的进化，尤其是免疫系统成分（如黄嘌呤氧化还原酶）在脂肪球膜中的进化整合。（5）乳糖合成的进化，特别是一些乳汁中发现的多种低聚糖的合成，这些乳汁包括单孔目动物、有袋类动物、犬型食肉动物和人类的乳汁。
