This article in the Japan Times mentions:
The next question is, how did love evolve? It’s quite easy to see why a mother who loves her child will be favored by natural selection. A deep degree of caring, nurturing and protecting — in short, loving — clearly helps the survival of a child. A mother might (and sometimes does, in animals as well as humans) sacrifice her life for the sake of her offspring. Such actions by a mother are likely to increase the survival of her offspring (and therefore her genes) and if so they, and love, will be favored by natural selection.
So much for the evolutionary advantage of love. As to the proximate, immediate cause of love, scientists have found that the mother-offspring bond in humans and other animals is mediated by the hormones oxytocin and vasopressin.
What researchers at University College London have now found is that romantic and maternal love activate many of the same regions of the brain. The implication is that maternal love is the evolutionary basis, the foundation, for romantic love.
The researchers, Andreas Bartels and Semir Zeki, of UCL’s Laboratory for Neurobiology, also found that love leads to a suppression of neural activity associated with critical social assessment of other people and negative emotions: The brain is told to go easy on people. The findings suggest that once you fall in love, the need to critically assess the character and personality of that person is reduced. The work could provide a neurological explanation for why love makes us blind.
Is it any wonder why so many men love to hear their mate call them Daddy? And why women have nurturing feelings towards their man?