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. 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. Allomothering by kin Hrdy states that the altruism of allomothers can be explained by Hamilton ’ s rule and therefore allomothers enhance their inclusive fitness by helping kin. However, in humans, bilocality and complex cultural norms around marriage or mating produce groups that may not be highly related suggesting that allomothering is not limited to kin. Despite varying and complex residential patterns, kin do appear to be strong sources of allomaternal care in many societies. Fathers, grandparents, older siblings and other close kin help in childcare, provisioning, protection and education. Allomothers are perhaps less important immediately after birth. Infants rely on the mother for milk to survive and mothers benefit from food provisioning by the fathers to produce sufficient amounts of milk for their infants. Infants whose mother ’ s die during childbirth have a low probability of survival, between 1-5\% in some pre-demographic transition populations, higher in post-demographic transition populations. If the mother dies during the first year of life the chance of survival increase to 35-50\%, and the effect of the mother ’ s death nearly disappears after the child reaches two. This indicates the important of parents during the first couple of years of life, but also demonstrates that once weaning is complete, allomothers are capable of rearing children to adulthood. Fathers The importance of fathers varies considerably, but many authors now agree that there is little impact on child survival from the loss of a father. Sear and Mace ’ s study of 15 populations found that in 53\%, the death of the father was not correlated with an increase in child mortality. The father does not directly feed an infant and it is possible that other males of the family or community can step in if something happens to the father. Kramer ’ s (2010) cross-cultural study found that in direct allomaternal care provided by fathers varies from less than 1\% (Alyawara) to nearly 16\% (Aka) with an average of 4.8\% across the populations studied. However, in many societies the father does play an important role. Among the Ache of South America, the loss of the father did affect the child ’ s survival. Meat sharing by hunters is an important part of Ache life and, while the majority of the meat acquired by a male may not go directly to the family, it is used to build relations and exchange for other goods. Interestingly, the father is not very involved in childcare among the Ache. The same study found that among the Hiwi (also of South America), where the father does provide direct childcare and food provisioning, the death of the father had no effect on child survival. A father ’ s most important contribution to children may be providing protection from other males, especially in groups that practice infanticide. Sear and Mace point out that many of the populations in the study look at the impact of the loss of a father on young children and suggest that since a father cannot provide direct nurshiment to breastfeeding children, their importance may come later in the child ’ s life. Fathers teach subsistence strategies to older children (for example, teaching hunting and trapping skills to older boys in hunter-gatherer societies). Allal et al. found that the marriage and fertility of women who do not have fathers may be impacted. Some hunter-gather populations in South America also have “partible paternity”, the idea that multiple men can impregnate a woman and all are considered the father, which could provide “back-up” fathers to children. Grandparents Grandmothers can care for children freeing the mother to engage in foraging or economic activities, or in the care of a child that has not been weaned. Likewise, grandmothers often continue to forage late in life to help with food provisioning for their grandchildren and a lactating mother. Child mortality in rural Gambia saw a significant decline when the maternal grandmother was present (see Table 4). In a comparison of nine populations on the proportion of direct childcare received by a child, Kramer found that grandmothers accounted for between 1.2\% (Maya) and 14.3\% (Mardu) of the total childcare. Sear and Mace determine that grandmothers do not have a universally positive effect on child survival and there is a difference between maternal and paternal grandmothers. Maternal grandmothers improved child survival in 69\% of cases while paternal grandmothers improved survival in only 53\% of observed cases. They also found that paternal grandmothers were detrimental in two cases and maternal grandmothers in one. Paternal grandmothers may on average be older than maternal grandmothers, due to common age differences in males and females at first reproduction. Paternal grandmothers may also be more reluctant to invest in their grandchildren due to the lack of certainty of paternity. The same study also found the timing of impact of paternal and maternal grandmothers varies, with maternal grandmothers having greater effects after the first year of life (allomaternal care) and paternal grandmothers having greater effects during pregnancy and in the first few months of a child ’ s life (help with tasks during pregnancy or causing high levels of stress to the mother during pregnancy). Grandmothers are often considered a significant source of allomaternal care and this fact has led to the “grandmother hypothesis”, suggesting that women developed long post-menopausal periods to help with their children ’ s offspring. This long lifespan after menopause is unique to humans and may help explain early weaning and high fertility rates. Hill and Hurtado argue that early reproductive senescence in females is an evolutionary dilemma since natural selection should favor continued reproduction. They test the grandmother hypothesis with data collected from the Ache and determine it does not support the idea that early menopause is maintained by natural selection favoring women who stop reproduction in order to invest more in their grandchildren. Despite Hill and Hurtado ’ s finding, grandmothers often account for a much of the allomaternal care seen in a variety of societies. Siblings Older siblings may be the greatest source of allomaternal care among kin. Kramer ’ s (see Table 1) comparison of nine populations found that siblings accounted for between 1.1\% and 33\% of the direct childcare received by a child. Older sisters appear to be more important than brothers for many of the groups in the study with sisters ranging from 5\% - 33\% and brothers 1.1\% - 16.3\%. Ivey (see Figures 1 & 2) found that among the Efe, both sisters and brothers contributed significantly to childcare. Sear and Mace found that five of the six studies indicated that child mortality increased survival of younger siblings. Older siblings, while still dependent on their parents. can engage in a variety of useful tasks depending on their age. It is possible that dependence on adult allomothers was not an early selective pressure for the development of allomothering in humans, but rather maternal – juvenile cooperation likely played a more important role. Extended family Other kin may be sources of allomothers when present, however evidence from the ethnographic literature demonstrates varied amounts of contribution and different impacts on the children. Aunts' and uncles' contribution varies depending on residential patterns, inheritance patters and resource allocation. Among the Kipsigis of Kenya, a child ’ s paternal uncle had a positive effect on reducing child mortality in the richer half of the sample but not on the poorer half, however for maternal uncles the effects were reversed with poorer families showing a greater reduction in child mortality. Local resource competition, namely conflict over land inheritance among the father ’ s brothers appears to account for the pattern of paternal kin effects. Others have found that the maternal aunts have similar effects in societies with female inheritance. Efe infants spend a significant amount of time in the care of aunts and male cousins. The second critique relevant to allomothering concerns human kinship distinctions. Schneider, along with other anthropologists, have argued that distinguishing between real and fictive kin does not always occur in human cultures and perhaps should be abandoned. The critique may be misunderstood to mean that humans cannot tell the difference between related and unrelated individuals. Maternity in humans, like many other animals, is known and the mother ’ s female relatives relatedness can be assumed by individuals with relative certainty. Humans are also unique as fairly stable pair-bonding allows for some degree of paternal certainty. In fact, Chapais argues that patrilineal kinship is a prerequisite for the flexibility of residential patterns seen in humans and this kinship is not culturally based but has a deep biological substrate upon which it is built. Gintis and Chapais arguments suggest that while kinship terms are often applied to individuals outside of related individuals, the relatedness of those individuals is known. A distinction is still useful and we see a difference in the contribution of allomothering by related versus unrelated individuals in many, if not most populations. Category:Wikipedia Student Program %DIFDELCMD < %DIFDELCMD < %%% Category:Parenting Category:Sociobiolog
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. 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. Allomothering by kin Hrdy states that the altruism of allomothers can be explained by Hamilton ' s rule and therefore allomothers enhance their inclusive fitness by helping kin. However, in humans, bilocality and complex cultural norms around marriage or mating produce groups that may not be highly related suggesting that allomothering is not limited to kin. Despite varying and complex residential patterns, kin do appear to be strong sources of allomaternal care in many societies. Fathers, grandparents, older siblings and other close kin help in childcare, provisioning, protection and education. Allomothers are perhaps less important immediately after birth. Infants rely on the mother for milk to survive and mothers benefit from food provisioning by the fathers to produce sufficient amounts of milk for their infants. Infants whose mother ' s die during childbirth have a low probability of survival, between 1-5\% in some pre-demographic transition populations, higher in post-demographic transition populations. If the mother dies during the first year of life the chance of survival increase to 35-50\%, and the effect of the mother ' s death nearly disappears after the child reaches two. This indicates the important of parents during the first couple of years of life, but also demonstrates that once weaning is complete, allomothers are capable of rearing children to adulthood. Fathers The importance of fathers varies considerably, but many authors now agree that there is little impact on child survival from the loss of a father. Sear and Mace ' s study of 15 populations found that in 53\%, the death of the father was not correlated with an increase in child mortality. The father does not directly feed an infant and it is possible that other males of the family or community can step in if something happens to the father. Kramer ' s (2010) cross-cultural study found that in direct allomaternal care provided by fathers varies from less than 1\% (Alyawara) to nearly 16\% (Aka) with an average of 4.8\% across the populations studied. However, in many societies the father does play an important role. Among the Ache of South America, the loss of the father did affect the child ' s survival. Meat sharing by hunters is an important part of Ache life and, while the majority of the meat acquired by a male may not go directly to the family, it is used to build relations and exchange for other goods. Interestingly, the father is not very involved in childcare among the Ache. The same study found that among the Hiwi (also of South America), where the father does provide direct childcare and food provisioning, the death of the father had no effect on child survival. A father ' s most important contribution to children may be providing protection from other males, especially in groups that practice infanticide. Sear and Mace point out that many of the populations in the study look at the impact of the loss of a father on young children and suggest that since a father cannot provide direct nurshiment to breastfeeding children, their importance may come later in the child ' s life. Fathers teach subsistence strategies to older children (for example, teaching hunting and trapping skills to older boys in hunter-gatherer societies). Allal et al. found that the marriage and fertility of women who do not have fathers may be impacted. Some hunter-gather populations in South America also have “partible paternity”, the idea that multiple men can impregnate a woman and all are considered the father, which could provide “back-up” fathers to children. Grandparents Grandmothers can care for children freeing the mother to engage in foraging or economic activities, or in the care of a child that has not been weaned. Likewise, grandmothers often continue to forage late in life to help with food provisioning for their grandchildren and a lactating mother. Child mortality in rural Gambia saw a significant decline when the maternal grandmother was present (see Table 4). In a comparison of nine populations on the proportion of direct childcare received by a child, Kramer found that grandmothers accounted for between 1.2\% (Maya) and 14.3\% (Mardu) of the total childcare. Sear and Mace determine that grandmothers do not have a universally positive effect on child survival and there is a difference between maternal and paternal grandmothers. Maternal grandmothers improved child survival in 69\% of cases while paternal grandmothers improved survival in only 53\% of observed cases. They also found that paternal grandmothers were detrimental in two cases and maternal grandmothers in one. Paternal grandmothers may on average be older than maternal grandmothers, due to common age differences in males and females at first reproduction. Paternal grandmothers may also be more reluctant to invest in their grandchildren due to the lack of certainty of paternity. The same study also found the timing of impact of paternal and maternal grandmothers varies, with maternal grandmothers having greater effects after the first year of life (allomaternal care) and paternal grandmothers having greater effects during pregnancy and in the first few months of a child ' s life (help with tasks during pregnancy or causing high levels of stress to the mother during pregnancy). Grandmothers are often considered a significant source of allomaternal care and this fact has led to the “grandmother hypothesis”, suggesting that women developed long post-menopausal periods to help with their children ' s offspring. This long lifespan after menopause is unique to humans and may help explain early weaning and high fertility rates. Hill and Hurtado argue that early reproductive senescence in females is an evolutionary dilemma since natural selection should favor continued reproduction. They test the grandmother hypothesis with data collected from the Ache and determine it does not support the idea that early menopause is maintained by natural selection favoring women who stop reproduction in order to invest more in their grandchildren. Despite Hill and Hurtado ' s finding, grandmothers often account for a much of the allomaternal care seen in a variety of societies. Siblings Older siblings may be the greatest source of allomaternal care among kin. Kramer ' s (see Table 1) comparison of nine populations found that siblings accounted for between 1.1\% and 33\% of the direct childcare received by a child. Older sisters appear to be more important than brothers for many of the groups in the study with sisters ranging from 5\% - 33\% and brothers 1.1\% - 16.3\%. Ivey (see Figures 1 & 2) found that among the Efe, both sisters and brothers contributed significantly to childcare. Sear and Mace found that five of the six studies indicated that child mortality increased survival of younger siblings. Older siblings, while still dependent on their parents. can engage in a variety of useful tasks depending on their age. It is possible that dependence on adult allomothers was not an early selective pressure for the development of allomothering in humans, but rather maternal – juvenile cooperation likely played a more important role. Extended family Other kin may be sources of allomothers when present, however evidence from the ethnographic literature demonstrates varied amounts of contribution and different impacts on the children. Aunts' and uncles' contribution varies depending on residential patterns, inheritance patters and resource allocation. Among the Kipsigis of Kenya, a child ' s paternal uncle had a positive effect on reducing child mortality in the richer half of the sample but not on the poorer half, however for maternal uncles the effects were reversed with poorer families showing a greater reduction in child mortality. Local resource competition, namely conflict over land inheritance among the father ' s brothers appears to account for the pattern of paternal kin effects. Others have found that the maternal aunts have similar effects in societies with female inheritance. Efe infants spend a significant amount of time in the care of aunts and male cousins. The second critique relevant to allomothering concerns human kinship distinctions. Schneider, along with other anthropologists, have argued that distinguishing between real and fictive kin does not always occur in human cultures and perhaps should be abandoned. The critique may be misunderstood to mean that humans cannot tell the difference between related and unrelated individuals. Maternity in humans, like many other animals, is known and the mother ' s female relatives relatedness can be assumed by individuals with relative certainty. Humans are also unique as fairly stable pair-bonding allows for some degree of paternal certainty. In fact, Chapais argues that patrilineal kinship is a prerequisite for the flexibility of residential patterns seen in humans and this kinship is not culturally based but has a deep biological substrate upon which it is built. Gintis and Chapais arguments suggest that while kinship terms are often applied to individuals outside of related individuals, the relatedness of those individuals is known. A distinction is still useful and we see a difference in the contribution of allomothering by related versus unrelated individuals in many, if not most populations. Category:Wikipedia Student Program %DIFDELCMD < %DIFDELCMD < %%% Category:Parenting Category:Sociobiolog
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