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The evolution of menstruation: A new model for genetic assimilation
Author(s) -
Emera Deena,
Romero Roberto,
Wagner Günter
Publication year - 2012
Publication title -
bioessays
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.175
H-Index - 184
eISSN - 1521-1878
pISSN - 0265-9247
DOI - 10.1002/bies.201100099
Subject(s) - decidualization , menstruation , biology , pregnancy , endometrium , physiology , fetus , endometriosis , evolutionary biology , endocrinology , medicine , genetics
Why do humans menstruate while most mammals do not? Here, we present our answer to this long‐debated question, arguing that (i) menstruation occurs as a mechanistic consequence of hormone‐induced differentiation of the endometrium (referred to as spontaneous decidualization, or SD); (ii) SD evolved because of maternal–fetal conflict; and (iii) SD evolved by genetic assimilation of the decidualization reaction, which is induced by the fetus in non‐menstruating species. The idea that menstruation occurs as a consequence of SD has been proposed in the past, but here we present a novel hypothesis on how SD evolved. We argue that decidualization became genetically stabilized in menstruating lineages, allowing females to prepare for pregnancy without any signal from the fetus. We present three models for the evolution of SD by genetic assimilation, based on recent advances in our understanding of the mechanisms of endometrial differentiation and implantation. Testing these models will ultimately shed light on the evolutionary significance of menstruation, as well as on the etiology of human reproductive disorders like endometriosis and recurrent pregnancy loss.