What would really nail this theory home, for me, is if fMRI studies demonstrated some kind of reduction in processing the physical sexual attractiveness of one's partner and others during the postpartum, pair-bonded state.
Analogously, analysis of what we polys term "New Relationship Energy," which mortals call "being in love," indicates that this phenomenon is associated with deactivation of neural areas associated with critical social judgment of others. Once the "decision" to be in love has been made (by your body, not by "you"), the brain ceases evaluation of the love object in social terms. (See, e.g., Andreas Bartels and Semir Zeki, "The neural correlates of maternal and romantic love." NeuroImage 21 (2004) 1155–1166.)
This is what Héloïse d’Argenteuil is making concrete in what is still the most righteous expression of romantic love I have yet encountered, from her first letter:
God is my witness that if Augustus, emperor of the whole world, thought fit to honor me with marriage and conferred all the earth on me for ever it would be sweeter and more honorable to me to be, not his empress, but your whore.
Its elevation above the self-interested social congress of the world is at the heart of the righteousness of romantic love.
I refer to this only by analogy. NRE is not at all the same phenomenon as the postpartum pair-bonded state that I have in mind. The early stage of love, as we polys remind ourselves with our terminology, lasts no longer than a year, maybe two, if you're lucky. (See, e.g., Enzo Emanuele et al, "Raised plasma nerve growth factor levels associated with early-stage romantic love." Psychoneuroendocrinology Vol. 31 Issue 3 (2006) 288-294.) The state of mind that must support monogamous love and continued investment despite postpartum disfigurement occurs after, and lasts much longer.
I don't imagine a woman who has gestated a baby would be eager to see the brain scan of her lover while he looks at her naked body. Nonetheless, it's hard to deny that this is important information for people considering whether to have a baby.