Allomothering, or allomaternal care, is parental care provided by group members other than the genetic mother. This is a common feature of many cooperative breeding species, including some mammal, bird and insect species. Allomothering in humans is universal, but the members who participate in allomothering vary from culture to culture. Common allomothers are grandmothers, older siblings, extended family members, members of religious communities and ritual kin (such as godparents).

The life history strategy of humans involves a long period of dependency, termed "secondary altriciailty" by Adolf Portmann, which should result in longer interbirth intervals. However, compared to other primates, humans have short interbirth intervals resulting in numerous overlapping dependents all without an increase in child mortality. Allomothering explains how humans can have children spaced only a few years apart and manage to raise multiple children at once. Food provisioning, help with childcare and investment in the child's learning can be provided by members of the community to help ease the mother's investment. Allomothering participants and specific helping behavior varies widely from group to group.

Cooperative breeding is a reproductive strategy that has been observed in birds, insects, and mammals. In cooperative breeding, parents receive support in childrearing from other members of the community. The parental support of helpers other than parents is known as allomaternal care (from the perspective of the mother, in species where both maternity and paternity is known it is often referred to alloparenting/allopaternal care) and can be carried out by kin and non-kin members of the community. Cooperative breeding is often seen to arise in monogamous mating systems with high coefficients of relatedness between group members and where females give birth to multiple offspring. The presence of allomothers is associated with reductions in interbirth intervals, increases in litter size, higher annual rates of survival. Cooperative breeding reduces the investment necessary for the parents of an offspring allowing the freed-up resources to be directed towards producing more offspring. Studies among meerkats suggest that while helpers incur great short term costs, long term costs are minimal or non-existent. Help by allomothers can be conditional upon health at the onset of the reproductive cycle, such as weight in meerkats, and helpers are able to modify their behavior to offset some of the short-term costs, i.e., increased time spent foraging and alternate breeding cycles in which they help. Cockburn shows that helpers among birds may benefit from increased numbers of non-descendant kin, increased access to territory and resources, increased access to mating options, increases in social status and longer time to acquire skills.

Cooperative breeding is common in many mammal species, but the type of care can vary greatly. Isler and van Shaik's survey allomothering in placental mammals found that 46% engaged in no help, 10% only provided protection, 3% provided only allonursing, 24% provided all forms of help other than provisioning and 16% provided complete help, including provisioning (see Figure 1, pg. 55).  Allomaternal help with provisioning was most common among members of Carnivora and Primates. The study also looked at correlations of allomaternal care and brain size, finding mixed results among many of the orders, however among Carnivora there was a correlation between male help and brain size and in Primates there was a correlation between allonursing and brain size. It has also been demonstrated that increases in allomothering among chimps is associated with a reduction in lactation efforts and shorter weaning times.  Hrdy argues that in order for cooperative breeding to occur, the underlying neural circuitry must be present in both sexes as well as pre- and post-reproductive aged individuals. This neurocircuitry includes a tendency to be attracted to, hold and protect infants, all of which are common among primates in various degrees.

Humans produce offspring that develop slowly and are incapable of moving or retrieving food for a lengthy period after birth. In animals that have infant altriciality and extended development, interbirth intervals are often longer to allow the mother to fully invest in one offspring before conceiving another. However, humans do not follow the pattern seen in other apes: human life history features relatively short interbirth intervals resulting in child-rearing costs that the mother alone cannot provide. Allomaternal care is a universal feature of human reproduction that helps provide additional childcare and other resources for the parents. While short interbirth intervals can negatively impact child outcomes, increasing the risk of child mortality, allomaternal care can reduce these negative outcomes while allowing interbirth intervals to remain short. When compared to other living primates, humans have short interbirth intervals (IBI), averaging 3.1 years in natural fertility populations, and total fertility rates (TFR) of 6.1 offspring versus interbirth intervals and total fertility rates for chimpanzees (IBI = 5.5, TFR = 2), gorillas (IBI = 3.9, TFR = 3) and orangutans (IBI = 9.2). Humans also have a unique period in their prolonged dependency, childhood, which allows for increased development and social learning.

The emergence of cooperative breeding in early hominins may explain several key life history traits such as larger brains and our demographic success around the globe. Isler and van Schaik analyzed life history traits such as first age of reproduction and interbirth intervals in primates and applied the resulting data to ancestral hominins and determined that without cooperative breeding the first age of reproduction for Australopithecus afarensis would be around 12.6 years and for Qafzeh Homo sapiens around 26.1 years. The predicted interbirth intervals would range from 6 to 8.4 years. Assuming some form or allomaternal care as early as A. afarensis, first age of reproduction comes down to 10.9 years and interbirth intervals are reduced to approximately 3.4 years. For Qafzeh H. sapiens, first age of reproduction is reduced to 22.6 years and interbirth intervals are around 4.7 years. Based on their study, Isler and van Shaik conclude that a change in lifestyle resulting in substantial increases in allomothering occurred early in the Homo genus. This implies that cooperative breeding has been an important part of human history for nearly two million years.

Demographic reconstructions of hunter-gatherer populations in the Pleistocene attempt to analyze the probability of having allomothers in a community and rely on assumptions about residential patterns in early humans. Kurland and Sparks (pers. comm. In Hrdy, 2006) provide estimates of several relatives' presence assuming different mortality rates. Under low mortality rates, the chance of primipara, a woman giving birth to her first child, having her mother around is around 50% and under high mortality rates the chance drops to 25%. The chance of having an older sibling around is much higher, as are the chances of having cousins. While this indicates that a new mother would have a least some close kin nearby to help with childcare, residential patterns may change these likelihoods. If humans were majority patrilocal, where males remain in natal groups and females disperse, we would expect lower maternal kin available for allomaternal assistance. This suggesting that mothers would need to rely more on paternal kin and unrelated individuals as potential allomothers, or for at least some of the mother's kin to temporarily reside with the parents during periods of high need. However, we know that humans are ambilocal or bilocal, meaning either males or females may disperse, which can impact the availability of maternal or paternal kin. Bilocality may have led to the diverse use of both kin and non-kin as allomothers in humans. Allomothering appears to also be tied to the environment, with increased levels of allomothering seen in regions of reduced climate predictability and lower average temperatures and precipitation.

Human females respond to social conditions during and immediately after pregnancy and may decide to abandon, neglect or commit infanticide if social support is lacking, if the infant is not considered viable (low birth weight, twins) or under certain extreme conditions (such as famine). Nearly all individuals show a response to infant crying and laughing, including fathers, virgin females, older children and even strangers. Oxytocin and prolactin, hormones released by mothers during lactation that may facilitate bonding, are also produced by males and others in the presence of a crying infant.