The child is the mother to the Homo sapiens.
By Sarah Blaffer Hrdy
Cambridge, MA: Belknap Press, 2009, 422 pp., $29.95, hardcover
The question, "What makes us "human?" keeps anthropologists, evolutionary psychologists, and philosophers in a continuing ferment of research, analysis, and speculation. New discoveries in human evolution make headlines in the New York Times, and the debates find their way into New Yorker cartoons--like the one of a woman at a cocktail party asking a man, "Are you a hunter or a gatherer?" In Mothers and Others, Sarah Hrdy aims to reconstruct the human evolutionary events stemming from ancient Pleistocene family life.
Hrdy proposes that some 1.8 million years ago, about the time when Homo erectus, a species now extinct, walked the earth, childrearing practices underwent a shift, so that the development of youngsters now depended not only on mothers but also on an array of other adults. This new mode of childrearing, which Hrdy calls "cooperative breeding," has psychological components such as mutual understanding, the impulse to give to others, mind reading, and other hypersocial tendencies. These cognitive and emotional transformations laid the groundwork for humankind's unique capacities for cooperation, intuition, sharing resources, and communicating ideas.
Hrdy says that she is drawing on new information
from comparative primatology and the ethnographic study of childhood in foraging societies, along with cognitive psychology, neuroendocrinology, and the flourishing new field of comparative infant development as well as from paleontology, sociobiology, and human behavioral ecology.
From these sources, she passes on a wealth of information to her readers. She comments that "new discoveries by evolutionarily minded psychologists, economists, and neuroscientists are propelling the cooperative side of human nature to center stage." She criticizes
textbooks in fields like evolutionary psychology [that] devote far more space to aggression, or to how men and women competed for or appealed to mates, than they do to how much early humans shared with one another to jointly rear offspring.
In a footnote she acknowledges that "this criticism could be applied to many of my own earlier publications."
Examining the dividing line between human and nonhuman apes, Hrdy explains that at one time, tool-use was assumed to be the factor that differentiated them--but the Great Apes use tools. Bipedal locomotion--walking on two legs--according to Hrdy, "bit the dust with the discovery of a fossilized trail of bipedal footprints left in volcano ash by australopithecines"--a four-million-year-old species that most anthropologists classify as a member of the human lineage, but that according to Hrdy was an ape with a brain "no bigger than a chimpanzee's." (Chimpanzees are humans' closest living relatives, and the two share a common ancestor with gorillas. The chimpanzee and human lineages separated between five and six million years ago, and a defining difference between the two is generally considered to be bipedal locomotion. So, although Hrdy labels the australopithecines as "bipedal apes," they are in fact on the human line. Their brains and body proportions are chimpanzeelike, as Hrdy correctly notes, because they lived only a million or so years after the separation between the human and chimpanzee lineages.)
But if using tools and walking erect do not distinguish human and ape, then what does?
Aha! In Hrdy's book, the care of infants and children holds the key to homininity. Ape youngsters, she says, are raised exclusively by their mothers. Ape mothers do not allow others to touch their babies, who are vulnerable to being killed by males or other females; understandably ape mothers are not trusting creatures. Apes are "self-serving," says Hrdy, whereas humans have peculiarly cooperative natures. Apes, she says, lack the mental and emotional capacity to cooperate, to read and share the feelings and concerns of others, and to coordinate action patterns--abilities necessary for cooperative child rearing.
In contrast to Great Ape babies, human infants take a long time to become independent. As they mature, they require provisioning and protecting--so much that a lone woman cannot provide everything they need. In the chapter appropriately titled "It Takes a Village," Hrdy (like Hillary Clinton, in her book of the same name) emphasizes the necessity of wider involvement in child rearing. She denies the once-widespread notion that hunter-gatherer mothers served as the exclusive caretakers of their babies. To the contrary, she says, human infants are held, provisioned, and tended by others in their social group. Among the Efe people of the Congo, recounts Hrdy, infants in their first days of life average fourteen different caretakers, including males--fathers, brothers, cousins, and sometimes grandfathers.
Because apes are raised exclusively by their mothers, Hrdy maintains that they are not the appropriate prototypes for reconstructing early hominin childcare. Instead she turns to marmosets, small-bodied monkeys from the South American tropics who belong to the family Callitrichidae. Callitrichidae helpers respond to noisily begging babies by providing them with beetles, spiders, frogs, and other protein-rich tidbits. This involvement of males as well as juveniles in infant care enhances maternal reproductive success for marmosets and, Hrdy argues, would also do so for humans. Cooperative breeding enabled hominins to wean babies sooner, and mothers could concentrate on keeping themselves fed. Both translate into shorter birth intervals, and over a lifetime, higher reproductive success. Humans, like these tiny distant relatives, breed unusually fast, and have, according to Hrdy, a marmosetlike ability to colonize and thrive in novel habitats.
Provisioning and protecting the young are not limited to marmosets, Hrdy points out. The behavior embodied in variations on "cooperative breeding," is found in diverse species from honeybees to birds and mammals, including mice, elephants, brown hyenas, and dogs. To reconstruct the past, sociobiologists such as Hrdy look for similar behaviors to compare across species, regardless of evolutionary relationship; in contrast, physical anthropologists focus on closely related species that have a shared evolutionary history, in this case chimpanzees and humans--an approach that Hrdy apparently rejects, at least for this behavior.
Involving others in the feeding and protection of the young requires individuals to be able to decode and empathize with the mental states of others, an ability Hrdy finds wanting in chimpanzees. Mothers need to be able to figure out who will help and who will hurt their offspring, especially because, Hrdy says, infanticide by strange males is a major source of infant mortality. She emphasizes that to relinquish exclusive access to the babies safely, a mother needed the example of "others who were competent and trusted, perhaps her own mother--a full grown and experienced caregiver familiar from birth." Such an association could be accomplished through residential patterns, (matrifocal instead of patrilocal) so that grandmothers and great aunts could pitch in with childrearing and gathering food, such as underground tubers, to share. Females past the age of reproduction have received little attention in evolutionary theory until recently, when the "grandmother hypothesis" suggested that they acted as mother's helpers.
Of course, we have no time machine that would enable us to reconstruct when during human evolution the shift in childrearing practices occurred. Hrdy speculates that children were slow to develop and costly to rear, therefore requiring "alloparents" as well as parents, by the time of Homo erectus, about two million years ago. Although Homo erectus had a brain only two-thirds the size of that of modern humans, Hrdy maintains that she was emotionally very different from the ancestors of nonhuman apes. Hominin children's dependence on nutritional subsidies from caregivers long after they are weaned demonstrates to Hrdy that sharing is a human universal.
What is missing, which seems central to Hrdy's argument about the evolution of childcare, is a discussion of what constitutes a "child." Anthropologist Barry Bogin, for instance, argues that a childhood stage between the ages of three and seven--that is, after infancy and weaning but before the "juvenile" stage--is what distinguishes Homo sapiens from apes. When during human evolution this stage developed is a point of contention. Research on the growth and development of wild chimpanzees and on fossils of human ancestors such as Neanderthals suggests that the extended childhood stage may have developed as late as Homo sapiens. If this turns out to be the case, Hrdy's reconstruction would apply to Homo sapiens, who appeared about 200,000 years ago, not to Homo erectus, who is much older.
As Hrdy develops her argument, the meaning of some of her terminology may be unclear, especially to readers not well-versed in evolutionary psychology or animal behavior. For instance, "cooperative breeders," "allomothers," "eusocial," and "altruism," have specific meanings within subdisciplines and do not translate clearly into other contexts, especially with regard to human behavior. Many of these terms go back to E.O. Wilson's 1975 book Sociobiology, in which, Hrdy says, "cooperative breeder became the umbrella term applied to any species with alloparental care and provisioning." However, "cooperative breeding" may recall to some readers an aspect of animal husbandry rather than a style of taking care of the young; and women today may regard the label of "breeders" as less than complimentary. Narrow labels limit thinking about the totality of reproduction, not discussed by Hrdy, which includes reaching sexual maturity, finding a mate, and successful coupling, as well as care for infant and juvenile offspring. Hrdy's terminology regarding nonhuman primates and fossils is also confusing. She uses "ape," for example, to include Asian living gibbons and orangutans, and African living gorillas and chimpanzees. Usually the term "Great Ape" excludes the gibbons but includes the orangutans, which are distantly related to gorillas and chimpanzees. However, the context suggests that Hrdy uses Great Ape to mean African apes only.
During the 1970s and 1980s, when anthropologists were bringing "woman the gatherer" into the evolutionary picture and when there were many discoveries in Africa of fossils from two to four million years old, the focus was on the early australopithecine stage. With a growing geological record of fossils that are less than two million years old, attention has shifted to the genus Homo. Homo erectus was one of the earliest species in this genus, although it is far removed from Homo sapiens. The closest relative of Homo sapiens, which separated from its lineage about 600,000 years ago, is Homo neanderthalensis. Much research into the Neanderthal genes and genome is currently going on, and this is where breakthroughs on issues such as growth and development will come from.
Placed in the context of current discussions about human evolution, Hrdy's focus on postreproductive women and the support they may have provided in childcare takes us into debates about menopause and longevity of the human species. It raises questions such as whether there was natural selection for extended life after the ability to ovulate, conceive, and carry a pregnancy. With a wealth of research and the ideas, Hrdy weighs in on childrearing, the life stages of older women, and the association between emotions and social interactions. She encourages our continuing debate on what it means to be human.
Adrienne Zihlman is professor of anthropology at the University of California, Santa Cruz; she writes about the role of women in evolution and co-edited The Evolving Female: A Life History Perspective (1997).
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|Title Annotation:||Mothers and Others: The Evolutionary Origins of Mutual Understanding|
|Publication:||The Women's Review of Books|
|Article Type:||Book review|
|Date:||Jan 1, 2010|
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