Evolutionary psychology of parenting

According to the parental investment theory, mothers are inclined to provide optimal care for their offspring due to the certainty of a genetic relationship. In regards to this, polyandry is rare in most societies as women will not take more than one husband in order to ensure the father with knowledge of the child's paternity and assistance with future care of their child from the father.[3] Brain circuitry also evolved to favor monogamous attachment around the same time that our ancestors developed upright bipedal abilities. The development of upright movement led to the development of females caring for their children by carrying infants in their arms instead of on their backs.[3]

Holding their infants in their arms led to greater bonds between mother and child. Upright bipedal abilities also developed stronger pairing-bonds between males and females as it became easier for males to protect just one female on the land instead of multiple females as they had done while living in trees. Natural selection favored males and females who had genes regulated towards forming pair-bonds because their young were more likely to survive, and brain circuitry gradually evolved to include attachment in parenting styles.

Women have adapted the ability to recognize infant facial expression of emotion, most especially negative emotion. This adaptation allows for the primary caretaker to develop a bond with their child leading to secure attachment during development. The "tend-and-befriend" hypothesis, which allows for the mother to care for and protect the child during detrimental situations, ensures offspring survival. Women are also able to create and maintain social networks that offer social protection for their offspring.[4]

Grandmothers have evolved mechanisms that allow them to invest in their grandchildren. Menopause might be an adaptation for older women to invest in care of their offspring and their children's offspring. A desire to improve inclusive fitness allows grandmothers, especially maternal grandmothers, to invest the most since they are guaranteed that the child carries their genes. Aunts will also invest more than uncles. Specifically maternal aunts will invest more than paternal aunts.[4]

Males have less investment in potential offspring and are generally less adept in their nurturing skills due to a greater emphasis on genetic reproduction, because any children that their mate births may or may not be their own. This phenomenon is termed paternal insecurity. However, "Human males do spend a lot of time investing in their kids and they invest quite heavily...That is a sharp contrast with other mammals, including our closest primate kin."[5] Research has shown that for this reason, fathers tend to invest more resources in children that look and smell like them.[6] Studies have demonstrated that when an infant is first born, males will experience decreased testosterone levels, making them less likely to be abusive, to commit infidelity, or seek divorce.[3] Increased levels of investment when a child is first born may be due to the fact that males want to protect their genes and assure the reproductive success of their offspring in order for their genes to be spread.

Human fathers are involved with their family life as social connections are beneficial and alleviate access to resources. Long term monogamous relationships between parental units are necessary for children's improved development. From an evolutionary perspective, the well-being of children during their development improves the probability of reproduction for the child, and therefore the continuation of the father's genes. Evolutionary perspectives do not see the behavior of fathers who abandon their families, solely based on passing down genetic information, but also through a social perspective as father involvement is an adaptation that has been shaped by the environment and experiences.[7]

In the modern case of divorce, fathers may feel less obliged to care for their children if guardianship of the child or children is granted to the mother, leading men to feel as if they do not need to be involved in the upbringing of their child. Remarrying, entering new romantic relationships, and having children with other women may also lead to fathers detracting from their parental investment towards their first born children. Divorced men finding new reproductive partners overrides their parental investment, as they focus on spreading their genes as widely as possible.[7]