Parenthood

Parenthood is an innate function of reproducing humans. A stabile relation with the biological father of the child has been evolutionary profitable for mothers and children. Quinlan & Quinlan found in their studies a strong relation between the bond in biological parents and the duration of breastfeeding, independent from the ability of the mother to secure support of female kin. Allo-parenting is good for the health of offspring, because it extends the protection breastfeeding offers. The total mean duration of breastfeeding amongst humans, however, is much shorter than what is to be expected when compared to that of our closest related other primates. Obviously earlier weaning provided an evolutionary profit above breastfeeding until the age of eruption of permanent teeth. According to Kennedy this probably has a relation to the development of the brain being served better by a higher protein adult diet. Sellen adds, that it may be a flexibility in adjusting the duration of lactation to meet both infant and maternal needs, whichever needs protection most in the survival of the species.
Quinlan R, Quinlan M: Human Lactation, Pair-bonds, and Alloparents. 2008, 1991):87-102.
Kennedy GE: From the ape's dilemma to the weanling's dilemma: early weaning and its evolutionary context. Journal of Human Evolution, 2005, 48(2):123-145.
Sellen DW: Evolution of Infant and Young Child Feeding: Implications for Contemporary Public Health. Annual Review of Nutrition, 27:123 -148