From the prehistoric past of the cave dwellers to the technological societies of today, what guarantees children’s survival and thriving better than anything else is the presence and the interest in them of their father. The presence and the interest of the mother is pretty much a given, but the father’s is not.
Bonding a man to his children is a process. At the very least, he needs to know the child is his. A mother is bonded to a child through powerful biological and chemical processes. A father, however, needs an extra reason to stick around. These extra reasons had to be so strong, they had to be spelled out at the level of sacred meanings to take root.
Monogamy is, thus, an evolutionary strategy and a survival mechanism. The biggest, most consequential pro-woman and pro-child revolution in human history – which is, of course, Christianity – came down so fiercely on the side of monogamy precisely because of this.