This Element builds on the mainstream theory of attachment and contemporary understanding of the environment of evolutionary adaptedness to address the origin and nature of infant-maternal bond formation. Sections 2 and 3 propose that attachment behaviors for protesting against separation and usurpation were compelled by infants' needs for close and undivided access to a source of breast milk, usually mothers, for three years to counter threats of undernutrition and disease that were the leading causes of infant mortality. Since these attachment behaviors would not have been presented unless they were compelled by maternal resistance, their arising is also attributed to parent-offspring conflict. Section 4 theorizes that the affectional nature of infant-maternal attachment originated within contexts of breastfeeding. Uniform and universal features of exclusive versus complementary breastfeeding, that could entail diverse experiences among multiple caregivers, may have shaped adaptations so that love relationships with mothers differ from those with nonmaternal caregivers.