Paternal Care

Anthropologists and other evolutionary biologists have long suggested that the evolutionary origins to human pair bonds and paternal care entailed some version of a “man the hunter” hypothesis. The idea is that during hominin evolution a sexual division of labor, in which men and women performed mostly complementary economic and reproductive tasks, emerged, with males specializing as hunters and women as gatherers and in providing offspring direct care. From the standpoint of paternal care, this type of scenario highlights a presumed deep evolutionary history in hominins of male indirect care in the form of resource provisioning, particularly of meat. This type of scenario enjoyed support from analogies drawn from recently studied hunter-gatherers and archaeological evidence such as stone tool cut marks on presumed prey bones as well as postulated meat-processing benefits derived from stone tool traditions tracing back 2.6 million years.

However, others have challenged such “Man the Hunter” scenarios on various grounds. One contention is that in hunter-gatherer societies men tend to focus on large game for purposes of showing off or costly signaling rather than for purposes of provisioning one’s wife and offspring. There is support for the view that among hunter-gatherer societies some of men’s provisioning efforts have wider social benefits than family provisioning, with enhanced male status perhaps translating into reproductive fitness benefits. However, there is also evidence—such as men targeting resources such as small game and honey that disproportionately flow to their wives and offspring, and men providing more resources to biological offspring than stepoffspring—that is consistent with provisioning.

More full consideration of potential human paternal care in the form of paternal provisioning entails several other issues. The history of hunting technology innovation, with spears first found approximately 400,000 years ago, and bows and arrows around 30,000 years ago, means that hominin male hunting efficiency in the past was likely much lower than that observed among recently studied foragers. Furthermore, a major feature of human reproduction is that hunter-gatherers interbirth intervals (time between successive births) of approximately 3-4 years are considerably lower than would be expected for an ape of our body size. Orangutan interbirth intervals in the wild are approximately 8 years, the longest of any terrestrial mammal, whereas interbirth intervals of chimpanzees and gorillas in the wild tend to be around 4-6 years. A combination of enhanced hominin female foraging efficiency (e.g., through use of technologies such as digging sticks) and food provisioning by other group members such as grandmothers and husbands enables humans to reproduce at faster rates—the lower interbirth intervals—than would otherwise be expected. To the degree husbands contribute to these reductions in interbirth intervals, the main benefit of paternal provisioning may be in facilitating faster reproductive rates rather than having impacts on offspring survival. There is no good analogy or homology for paternal food provisioning among Great Apes, indicating that whatever the evolutionary timing of its origin among hominins, and cautious over the mixed role of paternal care/costly signaling, this is a derived feature of humans.

Apart from food provisioning and “Man the Hunter” scenarios, human indirect paternal care could entail protective services. Considerable attention has been given to the potential role of infanticide prevention as an indirect form of paternal care among primates. Among Great Apes, an interpretation that gorilla male infanticide protection services seems consistent with the attribution of infant mortality to infanticide among a fair number of cases, and apparent role fulfilled by males of offspring defense against potential male group intruders. Among humans, infanticide prevention as an indirect form of paternal care among recently studied hunter-gatherers or across a wider array of contemporary societies does not seem well supported: while stepfather presence is associated with elevated offspring mortality and abuse risk in various studies, these cases are relatively rare and seem incidental to low male emotional attachment rather than adaptive reproductive strategies.

An additional potential form of indirect human paternal care is defense against predators. While relatively few hunter-gatherers die at the maws of predators such as leopards or large bears, it is reasonable to imagine that male protective services help account for some of this reduction in mortality, but also difficult to quantify this potential form of indirect paternal care.

Another form of indirect paternal care—passing along non-food material resources such as land or livestock—seems to have been derived recently in human history, consistent with the expanded array of forms of heritable wealth. Fathers may help their sons marry by providing resources such as livestock or land to serve as bridewealth in many societies. Fathers may leave an inheritance upon death consisting of money, a house, land, or other such material resources; often these are left with a spouse, with benefits further extended to offspring, making this also a form of indirect paternal care. Since accumulations of wealth of these sorts would only extend to some fairly recent complex hunter-gatherers and other societies relying on non-forager subsistence modes, these don’t project far in evolutionary history, and have no apparent analogy or homology among Great Apes.

As far as forms of direct paternal care, these can be assessed in various ways. Through studies of time allocation among hunter-gatherers such as the Hadza and Aka, scholars have helped clarify the amount of time fathers spend with their children primarily during waking hours, but also in some cases forms of direct care such as holding or carrying. Hunter-gather fathers, with the main exception of the Aka, spend a relatively small fraction of their waking hours in direct contact care of their young offspring, or even in close proximity. Part of that pattern seems related to the sexual division of labor, in which husbands and wives are often spatially segregated across the day, focused on different economic and social activities. Other caregivers such as mothers, primarily, but also grandmothers and other female relatives including older sisters play important roles in direct childcare. At nighttime, hunter-gatherer fathers tend to sleep in close proximity to a wife and their young children, providing additional time to tend to form attachments with their offspring. It is noteworthy that hunter-gatherer fathers tend to spend more time in direct care of children than is true of many agricultural and pastoralist societies, in part a reflection of greater polygyny among such latter societies which comes at expense to direct paternal care.

A final, possibly uniquely human, feature of paternal care is that related to offspring social or moral development. Fathers can contribute to their offspring’s social success by facilitating their children’s incorporation into beneficial social networks and fostering the development of beliefs and behaviors that yield reproductive success in the local environment (e.g., practice at being a good hunter or honey collector, with later social and reproductive rewards to follow). These types of paternal care often entail mostly modeling rather than teaching in hunter-gatherers or other small-scale societies, and are often sex-specific, with fathers tending to spend more time with their sons than daughters during their children’s late childhood and adolescence. The nature of father-son interactions tends to involve fewer conflicts in hunter-gatherers, probably in part because of a lack of heritable forms of wealth, compared with agriculturalists, pastoralists, and other kinds of societies.