In this 2015 article published in The Atlantic, author Adrienne Lafrance describes the biochemical reactions that take place within a woman as she starts her journey into motherhood. In fact, the Lafrance explains that the parenting instincts kick in for both new mothers and new fathers: "...the blueprint for mothering behavior exists in the brain even before a woman has children.Perhaps, then, motherhood really is like secret space in a woman's brain, waiting to be discovered. "Although only mothers experience pregnancy, birth, and lactation, and these provide powerful primers for the expression of maternal care via amygdala sensitization," researchers wrote, "evolution created other pathways for adaptation to the parental role in human fathers, and these alternative pathways come with practice, attunement, and day-by-day caregiving"...."
The research article on the father's brain being sensitive to childcare experiences can be read here:
http://http//www.pnas.org/content/111/27/9792.full