By Sarah Blaffer Hrdy.
Belknap Press of Harvard University Press, 2009
Reviewed by Judith L. Hand, A Future Without War.
Review published by the International Society for Human Ethology (ISHE)
Humans care, share, and empathize to a degree not remotely approached by other Great Apes. Why?
In Darwin, Competition, and Cooperation (1952), Ashley Montagu proposed that Darwin had been shaped by the industrialized, competitive world of his times and consequently, he and others overstressed the role of competition as a driving force in evolution. This trend continues in the "man-the-warrior" concept as the key to human cooperativeness (e.g., Holmes, 2008; Bowles, 2009). Montagu argued, citing even earlier proponents of cooperation (e.g., Kropotkin, 1939), that cooperation may be an even more important force.
With respect to human prosocial tendencies (i.e., to voluntarily do things benefitting others), Dr. Hrdy comes down solidly in the cooperation camp in Mothers and Others. She marshals evidence that humans are descendents of a Pleistocene species of cooperative breeders. Cooperation became possible because we inherited high levels of mutual tolerance, perspective taking, and other prosocial impulses from ancestors with alloparental care and provisioning of young. Humans didn’t invent complex cooperation—we inherited it and have elaborated upon it.
Chapter 1 sets the stage. Hrdy describes folks embarking on a journey by airplane. How would they respond to a crying baby, to being bumped by someone’s backpack? The travelers are busily reading minds, empathizing, and accommodating themselves to the needs of others. Imagine, she suggests, if the passengers were all chimpanzees. Using similarly vivid examples, frequently presented with a wonderful dry wit, Hrdy builds her case. Like Darwin, she constructs a solid foundation by presenting a plethora of data; her elegant writing enlivens material that might otherwise be boring. The essential background provided in Chapter 1 includes a review of the human family tree and our likeliest hominin ancestor, Homo erectus. Multiple examples demonstrate our "giving" and cooperative tendencies, even extended to others unrelated to us. Hrdy reviews relevant human traits (our "theory of mind," and "intersubjectivity"—the eagerness to share in other individuals’ emotional states), and documents how critical mind-reading skills appear early in a baby’s development.
Cooperative breeding is defined as young being cared for and provisioned not only by parents, but by other members of the group (alloparents). In subsequent chapters, Hrdy provides examples from many species. Cooperative breeding doesn’t mean constant cooperation: competition and coercion can be rampant. But Hrdy argues that in early hominins, alloparental care and provisioning set the stage for infants in the human family tree to develop in new (and highly cooperative) ways.
Hrdy distinguishes between behaviorally, anatomically, and emotionally modern humans and argues that the traits did not evolve simultaneously. Being born with giving impulses and empathic attitudes expressed in keen interest in the mental lives of others is, for Hrdy, the hallmark of emotionally modern humans, and likely goes back to a hominin ancestor hundreds of thousands of years before the emergence of either our big brains or language ability (pp. 66, 283).
Basing her thesis mostly on studies of nomadic foragers, Hrdy shows how resource sharing is essential to survival when raising slow-maturing, relative large, and very dependent young; this human condition is also likely true of early hominins. She compares food provisioning by women and men. Exchange of "gifts" establishes trusted exchange partners who may later become critical to one’s own survival. A careful comparison explains why, in her opinion, a bonobo-like model (Pan paniscus) rather than a chimpanzee-like model (Pan troglodytes) is more plausible for reconstructing a line of apes with the potential to evolve extensive care young by group members other than parents.
Hrdy is concerned that the current emphasis on intergroup competition may overshadow factors such as childrearing which she believes are perhaps as or more important for explaining our hypersociality.
" ... how much sense would it have made for our Pleistocene ancestors eking out a living in ... tropical Africa to fight with neighboring groups rather than just moving? ... Small bands of hunter-gatherers, numbering 25 or so individuals, under conditions of chronic climatic fluctuation, widely dispersal over large areas, unable to fall back on staple foods like sweet potatoes or manioc as some modern foragers in New Guinea or South American do today, would have suffered from high rates of mortality, particularly child mortality, due to starvation as well as predation and disease. Recurring population crashes and bottlenecks were likely, resulting in difficulty recruiting sufficient numbers. Far from being competitors for resources, nearby members of their own species would have been more valuable as potential sharing partners. When conflicts did loom, moving on would have been more practical as well as less risky than fighting." (p. 19)
In Chapter 2, Hrdy sets up a question pursued for several chapters: "Why Us and Not Them?" How are we similar to and different from other Great Apes and why? Here she compares human and Great Ape capacities for "mind-reading," reviews theories to explain the emergence of social mind-reading: the Mind-Reading Mums Hypothesis and the Machiavellian Intelligence Hypothesis. She concludes that both hypotheses are inadequate to explain pay-offs needed to initially make social mind-reading adaptive. We learn about mirror neurons. We learn how babies use eye contact and smiles to bond with their mothers and that baby chimpanzees are similarly equipped, suggesting that the potential for such mother/child bonding by this means was likely present in young hominins.
Chapter 3 reviews relevant aspects of Attachment Theory. Hrdy contrasts the remarkable willingness of human forager mothers to let others hold their young with other Great Ape females’ obsessive constant-contact-and-care. Her survey of primates reveals that in 40 to 50% of 276 species, alloparents provide care, but stop short of provisioning, the young of others. Provisioning is characteristic of "full fledged cooperative breeders." In later chapters Hrdy gives examples of human alloparents not only breast feeding the young of others, but masticating and passing hard-to-digest foods to infants. She reviews genetics and behavior of callitrichids (marmosets and tamarins), the only primates other than humans that qualify as full-fledged cooperative breeders. For primates, the callitrichids are remarkably fast breeders and rapid colonizers—a provocative demographic implication of cooperative breeding not part of her definition, but which is also typical of our species (humans have the fastest reproduction of any of the Great Apes and have colonized most parts of the globe). Among the negative aspects of cooperative breeding: both callitrichid and human females that perceive themselves to be short of alloparental support will abandon their infants, a rarity for all other primate mothers.
Chapter 4 reviews the ways human babies, "connoisseurs of commitment," solicit the attention of parents and alloparents. We consider out-of-home day care, the positive effects of fathers, the positive effects of multiple caregivers on development of world view, Israeli kibbutzim, whether to sleep alone or not, what factors correlate with such traits (in adults) as empathy, dominance, independence, and achievement orientation, development of the concept of self vs. others, and the child’s perception of the world as insecure and dangerous or "giving."
Chapter 5 considers who are likely alloparents, why they help (the underlying social, ecological, hormonal conditions), and the roles of men and the nuclear family versus the extended family. Her conclusion: the key to maximizing human child survival has been flexibility—alloparents take up slack a mother cannot fill, and mothers move opportunistically to where they can receive the most help.
Chapter 6 summarizes the conditions conducive to the evolution of cooperative breeding in a wide-range of non-primate and non-mammalian species (from wolves, to bee-eaters, to paper wasps), illustrating how these species fit the definition. She reviews topics such as coercion and competition, and cases where alloparental care is nearly as self-serving as altruistic. She reviews behavioral and physiological changes associated with breeding status.
In Chapter 7, Hrdy argues that once selection favors parents and alloparents that are responsive to babies, a self-reinforcing evolutionary process starts in which caregivers become more responsive to infant cues and infants to the intentions and moods of caregivers. We consider the attractive qualities of young animals (including the cute baby phenomenon), and the neurophysiological responses of post-partum mothers and others to babies. In passages relevant to how important relatedness is to altruism, cross-species adoptions are described: " ... once members of a given population have been selected to respond to infant cues by helping, care-givers need not be close relatives in order to respond" (p. 212).
Effects of kin on infant survival are stressed in Chapter 8. Hrdy tucks into Chapter 8 a survey of behaviors used by women to cultivate potential allomothers that may not be kin: friend-"sisters;" honorary naming devices such as "god-parents"; and polyandrous mating. Genetic evidence is adduced to illuminate ancient residence and movement patterns. She describes the flexible, often bi-local, residence patterns of hunter-gatherers: when kin are nearby, it is safe to trust someone else with your infant and so residence patterns affect shared care. Moreover, infant survival is significantly affected by grandmothers (a maternal grandmother’s presence is more beneficial than a paternal grandmother’s). Hrdy also considers grandfathers’ potential benefits. She considers why human females live after menopause for an astonishingly long time. Throughout the book, the author presents human behavior as it is, warts and all, as when she describes the sometimes harsh treatment of grandmothers (or grandfathers) who have outlived their usefulness.
In the final chapter, "Childhood and the Descent of Man," Hrdy moves her analysis to modern times by reviewing effects on human sociality when nomadic hunter-gatherers took up settled living: higher population densities, accumulation of "property" (she touches on how these changes would promote a shift from cooperation between groups to war between groups), emergence of patriarchy, and what we see in our postindustrial era, including altered patterns of child care.
The altered patterns of child care spark her surprising final twist: Hrdy speculates on whether we are losing the "art of nurture." Traits not used and not key to reproductive success can be lost (p. 293), and humans are continuing to evolve, quite rapidly (p. 292). What then, she asks, are the potential evolutionary effects of rearing children who are not living in intimate contact with a variety of caregivers? "Within the first two years of life, infants ... reared in responsible caretaking relationships develop innate potentials for empathy, mind reading, and collaboration ... . Such behavior is the outcome of complex interactions between genes and nurture ... .Thus, the development of (these) innate potentials is far from guaranteed." (p. 286)
Many children raised without extensive social contact display "disorganized attachment," poor empathy, and poor cooperative skills, yet reproduce just fine. She sees our very distant progeny as being bipedal, symbol-generating, intelligent, and at least as Machiavellian as chimpanzees. They will still be cooperating but, she wonders in the book’s last line, will they also still be "human in ways we now think of as distinguishing our species—that is, empathic and curious about the emotions of others, shaped by our ancient heritage of communal care?" (p. 294).
I find few faults with Mothers and Others. Hrdy is an exceptionally careful writer. She backs up assertions with solid citations and chooses words carefully; speculation is stated as such or is modified as "likely." The subject of the evolution of human cooperation and altruism, however, is controversial, and she chose to include material from an extraordinarily broad range of subject areas. The text occasionally evokes unanswered questions, although end notes often provide further insights without making the book’s size too formidable. I expect that experts in some subject areas will find points of conflict or issues they would have liked her to cover more thoroughly. I found the text occasionally repetitive, a small quibble.
For example, I’m interested in gender differences that might influence social behavior relating to aggression, conflict resolution, and the origin and causes of war (Hand, 2003, 2006). Empathy is a key trait. I argue that greater empathy characteristic of women in general compared to men in general may facilitate a stronger female (than male) aptitude/preference for creating social stability (e.g., a more ready willingness to negotiate or compromise, and greater foresight – e.g., Kolb, 1997; Rosener, 1997; for opposing views see Watson, 1997; Powell, 1997) that, in turn, opposes fighting and killing to resolve conflicts. Because Hrdy’s text often stresses the contribution of females, much more than males, in alloparenting, I would have liked to see an exploration of whether capacities for "mutual understanding" and empathy among hunter-gatherers differ between adult males and females. A book about cooperation might also have included recent theoretical models such as the work of Martin Nowak (Nowak, 2006; Wax, 2008) that support the adaptive importance of cooperation to evolution at all levels: e.g., molecular, ecological, and behavioral.
The photos of interacting apes and of hunter-gatherers are often charming. The extensive citations make this book a must-have reference for anyone concerned with the evolution of human prosocial behavior and altruism. Those interested in the origins of inter-group aggression and war and their (potential) contribution to cooperative behavior should also consider this required reading. Clearly, Hrdy has made a strong, compelling case that sophisticated abilities for cooperation that could avoid fighting go back into our very deep past. I predict that "man-the-warrior" advocates will find reading Mothers and Others both thought-provoking and a pleasure. Mothers and Others is a major contribution to a rapidly surging appreciation for the adaptive power of cooperation as a force shaping evolution.
Judith L. Hand is a pioneering peace ethologist, the author of Women, Power, and the Biology of Peace and a collection of essay from her website by the same name, A Future Without War (www.afww.org). She completed her Ph.D. degree in Animal Behavior at the University of California, Los Angeles, in 1979, her subfields being ornithology and primatology. After completing a Smithsonian post-doctoral Fellowship in Washington, D.C., she taught briefly at UCLA and published on communication and conflict resolution. She is a published novelist under her name and also the nom de plume Judith Leon. Currently, she writes, speaks, and networks to promote understanding of why and how we can end war.
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