Finn C A
Department of Veterinary Preclinical Sciences, University of Liverpool, Neston, South Wirral, United Kingdom.
Q Rev Biol. 1998 Jun;73(2):163-73. doi: 10.1086/420183.
Although adaptive explanations for menstruation go back at least twenty-five hundred years, in the last decade two new hypotheses have been advanced. The first suggests that menstruation evolved to cleanse the uterus of pathogens introduced by sperm, and the second argues that the function of endometrial regression (with the associated menstruation in humans) is to save energy by getting rid of tissue, rather than maintaining it in the absence of an available blastocyst. Both these suggestions may be questioned on the grounds that they do not take into account the physiology of the reproductive processes involved. Menstruation is not an independent physiological process and is unlikely to have been selected for independently of the evolutionary events that led to it. Furthermore, most primitive menstruating animals would have menstruated infrequently, and many may have reproduced or died without ever menstruating. In order to provide a context for understanding how menstruation may have come about, the evolution of the female vertebrate reproductive tract is briefly reviewed. In later stages, the coevolution of the embryo and uterus resulted in an intimate association between the trophoblast and the uterine blood vessels. As the embryo became more invasive, the uterus responded with increased cellular growth and differentiation of the endometrium to accommodate it. This reached its peak in mammals (such as rodents and humans), where the embryo passes through the epithelium into the endometrial stroma, which responds with differentiation of cells and blood vessels. Progesterone, secreted after ovulation, plays a crucial role in preparation for pregnancy. In addition to its well-known effects on the uterus, progesterone may be important in suppressing the inflammatory reaction that would be expected in response to the presence of a foreign body, such as an embryo. It is also suggested that vascular and cellular differentiation of the endometrial stroma has evolved by adaptation of the inflammatory (granulation tissue) reaction. When progesterone levels fall at the end of the cycle, there is tissue breakdown and bleeding. The uterus then reforms for the next ovulatory cycle. It is shown that the female reproductive tract has multiple functions that must occur in sequence. The coevolution of the embryo and maternal tract thus led to the close contact of two genetically different tissues, and problems such as the inflammatory reaction had to be overcome. Menstruation is a necessary consequence of these evolutionary changes, and needed no adaptive value in order to evolve.
尽管对月经的适应性解释至少可以追溯到两千五百年前，但在过去十年中，人们提出了两种新假说。第一种假说认为，月经的进化是为了清除精子引入子宫的病原体；第二种假说则认为，子宫内膜退化（以及人类相关的月经）的功能是通过去除组织来节省能量，而不是在没有可用胚泡的情况下维持组织。这两种假说都可能受到质疑，因为它们没有考虑到所涉及的生殖过程的生理学。月经不是一个独立的生理过程，不太可能独立于导致它的进化事件而被选择。此外，大多数原始的有月经的动物月经都不频繁，而且许多动物可能在没有月经的情况下就繁殖或死亡了。为了提供一个理解月经可能如何产生的背景，本文简要回顾了雌性脊椎动物生殖道的进化。在后期阶段，胚胎和子宫的共同进化导致滋养层与子宫血管紧密相连。随着胚胎的侵入性增强，子宫通过子宫内膜细胞的生长和分化增加来做出反应以适应它。这在哺乳动物（如啮齿动物和人类）中达到顶峰，在这些动物中，胚胎穿过上皮进入子宫内膜基质，子宫内膜基质通过细胞和血管的分化做出反应。排卵后分泌的孕酮在为怀孕做准备方面起着至关重要的作用。除了其对子宫的众所周知的影响外，孕酮在抑制对异物（如胚胎）存在所预期的炎症反应方面可能也很重要。也有人认为，子宫内膜基质的血管和细胞分化是通过炎症（肉芽组织）反应的适应而进化的。当周期结束时孕酮水平下降，就会出现组织分解和出血。然后子宫为下一个排卵周期进行重塑。研究表明，雌性生殖道具有多种必须按顺序发生的功能。胚胎和母体生殖道的共同进化因此导致了两种基因不同的组织紧密接触，并必须克服诸如炎症反应等问题。月经是这些进化变化的必然结果，其进化不需要适应性价值。
