Mother Nature: A History of Mothers, Infants, and Natural Selection
Publication Date:March 2001
Reviewed Title:Along the Evolutionary Biological Trail A review and commentary on: Mother Nature: A History of Mothers, Infants, and Natural Selection (1999)
Reviewed Publisher:Pantheon Books. 723 pages. ISBN: 0-67944-265-0.
Mother Nature: A History of Mothers, Infants, and Natural Selection by Professor Sarah Blaffer Hrdy, an emeritus professor of anthropology at the University of California at Davis, is a monumental multidisciplinary treatise that summarizes her life's work and which, I believe, is destined to become a classic in the field and a core text for many university courses and seminars on Mother Nature. How does one provide a fair "review", in about 2,500 words, of a monumental text with 55 pages of Notes and 44 pages of bibliography? It is a mission impossible. So the following observation, by necessity, has to be selective and limited. Because of my own research on some of the issues Hrdy investigates I have also added some analysis, commentary and suggestions.
Hrdy's treatise is really two books in one. The first part, a sweeping scientific overview of evolutionary biology and its implications for human maternal behavior, should have been left to the special interests of the scientific community interested in documenting the early "evolutionary trail", which has little predictive validity for human primate maternal behavior. As interesting as the maternal behavior of insects, birds and fishes may be, they have no predictive validity for human maternal behavior. Such material, invaluable in its own right, detracts from the ultimate mission and audience intended by this text-contemporary mothers who also have a "mission impossible" i.e. to do what is not only best, but necessary, for the healthy development of her infant/child.
That portion of the "evolutionary trail" most relevant to understanding the complexity of a homo sapiens mother is, of course, the primate order, not even the mammalian class. Hrdy has shown that the body of evidence about the primates is so extensive and characterized by such great variability, that predictive validity from infrahuman primate specific behaviors to human primate specific behaviors is fraught with great difficulty (Chapter 4: Unimaginable Variation and Chapter 5: The Variable Environments of Evolutionary Relevance). A problem I encountered is the ease with which Hrdy can move from insects, birds and fish to primates in her comparative analyses throughout the text. Hrdy has, however, identified some infrahuman primate maternal behaviors that have high predictive relevance and validity for homo sapiens maternal behavior, but not many.
One of the great challenges is sorting out the proportional relevance of genetic biology from non-genetic biology from culture in accounting for the high variability of maternal behaviors along the evolutionary trail. Another challenge is trying to determine the ultimate importance of Darwinian evolutionary biology for understanding the complexity of human maternal primate behavior.1
Hrdy quotes the sociobiologist Mary Jane West-Eberhard who maintains that, "Nothing is genetically determined in the sense of determined by genes alone. No gene is expressed except under particular circumstances. It's a kind of biological illiteracy to talk about a gene for anything other than a particular protein molecule" (p. 57). Hrdy reinforces this point, indicating that, "No gene or set of genes, or even any one mechanism influencing people to favor kin, has been identified. We do not know even a fraction of the ways that kin selection works" (p. 63). These observations are critical in understanding the crucial role that culture or environment plays in the ultimate structure of the complexity of maternal behaviors and the limiting role that Darwinian evolutionary biology must have on human maternal behaviors when compared to the forces of cultural evolution.
A comparison with homo sapiens closest living genetic relative-the bonobo chimpanzee is illustrative. Genetic (DNA) communality between the two species has been given at about 98% but some estimates, derived from the data in Jared Diamond's The Third Chimpanzee, is closer to 99.1% communality. The genetic distance between the bonobo and the common chimpanzee is estimated at 0.7% DNA with a difference from homo sapiens at about 1.6% of DNA. Yet, the bonobo chimpanzee is the most peaceful and non-violent primate on the planet while homo sapiens is the most violent primate on the planet. The bonobo is also the most nurturing of primates. The bonobo infants are breastfed to about 4 years of age and the male offspring (the female not as long) are carried on the mother's back until they are adolescents. This may well explain the non-violence of bonobo males against offspring, females and toward each other.
How can "evolutionary biology" explain this behavioral difference between bonobo and homo sapiens, when Hrdy observes, "scientists estimate that a mere 50 or so genes-out of the vast number of genes that chimpanzees and humans share in common-account for the cognitive differences between the two species; that fractional genomic disparity combined with differences in several regulatory genes that control the timing of gene expression make all the difference" (p. 392). Homo sapiens have the worst record for violence against infants and children, as the child abuse, homicides, abandonment and neglect statistics reviewed by Hrdy reveal. Parents continue to be the greatest perpetrators of child maltreatment (80%), as recorded by a recent Bureau of Justice Statistics report, Homicide Trends in the U.S. In that report, mothers and fathers were equal (31%) in the murder of all children under age five (1976-98). Yet, Hrdy notes, " no wild monkey or ape mother has ever been observed to deliberately harm her own baby" (p.179).2
What does this have to say about the relevance of Darwinian evolutionary biology to understanding human parental homicidal behavior? The small genetic difference between these species raises questions about the meaningfulness of attempting to explain these extreme behavioral differences in terms of "gene differences" or to attempt to extract meaning from larger genetic differences along the biological evolutionary trail in order to explain human maternal behavior-a fruitless inquiry, given the function of genes. Clearly, a bonobo genome project to compare with the human genome project that would identify the distribution of those genes on which chromosomes that are present in humans but not bonobo would be invaluable. Are there any mammalian or infrahuman primate universals of maternal behavior that can be reliably applied to human maternal behavior? Hrdy notes that lactation/ breastfeeding is one such behavior because there are no infrahuman primates which do not breastfeed their young. This fact seems to constitute a "maternal universal".
Yet, only 14% of American mothers are still breastfeeding at age one year of the child, which carries its own adverse consequences. In this respect, it should be noted that human breastmilk contains some 400 biochemical nutrients compared to about 30 in infant formula milk and contains numerous vital nutrients for normal brain and immunological development of the infant/child that are not present in infant formula milk. One significant example is tryptophan, an amino acid richly present in colostrum and breastmilk but absent in formula milk. Tryptophan is converted to brain serotonin, deficits of which, results in depression and violence. Unfortunately, Hrdy failed to note the significance of this aspect of breastmilk nutrients for normal brain development and behavior, particularly, when breastfeeding is considered to be a cultural option by many human mothers.
Hrdy rightly notes another universal maternal behavior in infrahuman primates, high mother-infant body contact. Carrying of the infant/child on the body of the mother is characteristic of all infrahuman primates and hominids. She notes, "Great Ape mothers carry their infants wherever they go. Fathers, by comparison, are rarely in direct contact with babies" (p.205). She adds, "It was the mother who continuously carried the infant in skin-to-skin contact-stomach to stomach, chest to breast. Soothed by her heartbeat, nestled in the heat of her body, rocked by her movements, the infant's entire world was its mother" (p. 98). Clearly, newborn/infant carrying is another "infrahuman primate maternal universal" that has been largely lost to homo sapiens mothers. Body movement (vestibular-cerebellar simulation) is the external umbilical cord-the primary sensory stimulation in utero-that conveys continuing basic trust and security to the newborn/infant. Experimental and cross-cultural data, not reviewed by Hrdy, clearly support the adverse consequences of this essential sensory loss in homo sapiens maternal behavior.
Hrdy did review the Harlow studies of experimental separation from their mothers about ten days after birth of newborn rhesus monkey, which were than reared in single cages but in a colony room, selffeeding from bottled milk and with no physical contact with other animals or humans. Yet she neglected to review what is probably the single most important study conducted in this genre of studies that of Dr. William Mason also at the University of California-Davis Primate Research Center-but from whom she quotes in another context. Mason's singular contribution in this most important study was the demonstration that the "maternal-social deprivation syndrome", associated with mother-infant separation, could be prevented by rearing the isolated infants on a "swinging mother surrogate", compared to rearing infants on an identical mother surrogate which did not move. This artificial body movement restored the tradition of the Great Ape Mothers and prevented the classic depression, chronic stimulus seeking behaviors and violence from appearing and permitted normal social interactive behaviors to develop.
Cross-cultural studies conducted which I personally have conducted, demonstrated that mother-infant carrying during the first year of life could predict with 80% accuracy the peaceful or violent nature of 49 "primitive" cultures that were distributed throughout the world. The peaceful or violent nature of the remaining 10 cultures could be accurately classified based upon whether premarital coitus was permitted or punished.
The other body of experimental data not reviewed by Hrdy, but which I believe are significant to her thesis, are the brain-behavioral studies which I initiated when I was Health Scientist Administrator, Developmental Behavioral Biology Program, National Institute of Child Health and Human Development, NIH. A number of brain studies on mother-deprived monkeys documented structural and functional brain abnormalities when compared to mother reared monkeys. Much of this data is 25-30 years old and can be viewed at
The failure of mother love or lack of "bonding/attachment" in the mother-infant relationship is more damaging upon the infant/child and upon culture than even Hrdy has described. Certainly, a review of this data would have altered substantially her conclusions reached in Chapter 23-Alternative Paths of Development-and her section on Blaming Mothers for Sociopaths. While admitting that, "Even if a disproportionate number of people who grow up to be sociopaths were avoidantly attached, one has to wonder why their 'internalized working model' didn't do a better job of correcting itself when things improved" (p. 513), thus mitigating the role of mother in the development of anti-social personality disorders of her children. This does not mean that "mother is blamed" but rather, it is the failure of society, community and family to support mothers being nurturing mothers.
The reason that the "internalized working model" of John Bowlby3 does not self-correct is that there is developmental brain dysfunction/ damage induced by somatosensory affectional deprivation (S-SAD) through failed bonding/attachment in the mother-infant/child relationship; and the failure to rehabilitate the somatosensory affectional system-virtually all "therapy" is "cognitive". If she had surveyed this and other data, Hrdy could not have concluded, "We don't know if, at a physiological level, brutal monkeys and brutal men are motivated in anything like the same way" (p. 239). On the contrary, this is exactly the lesson that has been learned by the Harlow, Mason, Mitchell, and Suomi genre of primate maternal-infant separation studies.
However, this does not mean that there are not other causes of violence and brutality. Hrdy's rightful and strong defense of kinship allomothers in evolutionary times-to support mothers-unfortunately does not translate to our cultural time. Kinship allomothers are rare in our culture and stranger daycare allomothers are not allomothers at all-just strangers. Infant and early child day care is not the solution to the problem, as Hrdy and many feminists believe. Bowlby's observation is very relevant here, when he stated that it is "very difficult to get people to look after other people's children."
The sections on "Not So Coy Females" and "Mother's Sexual History as a Maternal Effect" are significant contributions to Hrdy's text. The reporting by Hrdy and others of the development of multiple male mating infrahuman primate females with its linkage to non-violence of such males against these females and to non-alpha male troop organization is of great bio-cultural evolutionary significance, in my view. Hrdy notes, "Consider the case of chimpanzees. A female chimp mates on average 138 times with some thirteen different males for every infant she gives birth to. Female bonobos also mate many more times than is necessary for conception, as do other species of primates living in multimale groups, such as barbary macaques and baboons" (p. 85). Clearly, the emergence of multiple male mating females dramatically alters the future of sexual function, which has had its primary purpose of reproduction in estrous-bound females living in alpha organized troops and other sexually estrous-bound mammals. The bonobos, our closest genetic relative, are the best example of multiple male mating infrahuman primate females whose sexual activity is not bound to the estrous cycle and is highly linked with male/female nonviolence and high nurturance of offspring. Similar relationships were also found in human "primitive" cultures which I have researched. Various matrilineal/matrilocal human cultures have been primarily characterized as highly nurturant to children, with low violence/warfare. These cultures permitted premarital and extramarital sex, had large extended families, had a low or absent bride price, and were characterized by the absence of a high god in the culture among other social-behavioral characteristics. The opposite relationships were found in the patrilineal/patrilocal cultures plus the presence of other social-behavioral characteristics, e.g. polygyny is common, abortion is punished with high desire for children, slavery is practiced, male genital mutilation is present and caste system is present.
These relationships were statistically significant where sample sizes ranged from 15 to 395 cultures with varying degrees of percentage of common variance among the variables. In the statistical analysis of the relationship between premarital sexual relationships being permitted or punished, it was found that 67% of 24 cultures that permitted premarital sex were non-violent while 73% of 11 cultures that punished premarital sex were highly violent. These relationships were stronger for extramarital sex where 74% of 19 cultures that permitted extramarital sex were non-violent and 78% of 23 cultures that punished extramarital sex were very violent. The peaceful cultures were predominately matrilineal/matrilocal, the violent cultures were predominately patrilineal/patrilocal. These studies can also be seen at
Unfortunately, these published data were not reviewed by Hrdy, which would have strengthened and altered her interpretation and conclusions concerning the relevance of infrahuman primate multiple male mating females to human multiple male mating females where female sexual function is not bound to the estrous cycle. Hrdy's discussion of the Canela tribe of the Brazil Amazon by Dr. Crocker's, extraordinary detailed documentation of these relationships is given validity by the larger statistical studies of the relationship between high nurturance (pleasure) with non-violence; and low nurturance (pleasure deprivation) with high violence-from mother/ infant relationships to youth and adult sexuality. Given the hazards of living in a patristic authoritarian culture, the options of exercising sexual choice by human females for either reproductive or non-reproductive sexuality, dictates caution over the exercise of these newly found behaviors in the bio-cultural evolution/revolution of homo sapiens, a caution well-noted by Hrdy.
From my perspective, the evolutionary transition from a female sexuality that is bound to the estrous cycle to one that is not, where male/ female sexuality serves more than a reproductive function with male acceptance of multiple male mating females, may well mark the end of the controlling interest of Darwinian evolutionary biology that yields to the newer controlling interest of bio-cultural evolution-a "bridge too far" apparently for Hrdy to cross.
The greatest shortcoming of Hrdy's text on Mother Nature is the failure to indict the theistic/patristic cultures of modern homo sapiens. Under this rubric the female of the species is kept unequal and subordinated to the power and authority of the male of the species, particularly with respect to the free and autonomous expression of her sexuality. The role of the theistic/patristic religions in this process is the great enemy of woman as woman and woman as mother and is ultimately man, himself-as allofather and egalitarian. It is clear to me that if the fruits of the new bio-cultural evolution of homo sapiens are to be realized, it will be necessary to dismantle the tyranny of the theistic/patristic cultures of the world. The neglect of this topic by Hrdy is the major flaw in her monumental and important work on Mother Nature. What is Professor Hrdy's final position on Mother Nature, as a scientist, feminist and mother?-an impossible balancing act in my view. In her own words, "After the first weeks of living with a baby girl whom mostly slept or quietly nursed through seminars, it became increasingly apparent that in the world I lived in, caring for a baby was incompatible with concentrated work. A new baby's terrifying vulnerability, the magnitude of the responsibility, and the insatiable demands that kept me on-call twenty-four hours a day, came as a shock. Yet, as a primatologist in the post-Bowlby era, what could I do but turn my life over to her?" (p. xiv).
1. Some modern biochemists and biologists seem to have returned to the notion that perhaps the theories of Jean Baptiste Pierre Antoine de Monet Lamarck (1744-1829) and not those of Charles Darwin hold more credence. Lamarck's theory of evolution, or Lamarckism, asserts that all life forms have arisen by a continuous process of gradual modification throughout geologic history. To explain this process he cited the then generally accepted theory of acquired characteristics, which held that new traits in an organism develop because of a need created by the environment and that they are transmitted to its offspring.
2. But this is not true of males of the North Indian Langur and Hamadryas Baboon species. Although these primates do not seem to kill their own offspring, they do kill any infants previously sired by males whose harems they preempt by aggression.
3. As is well known, John Bowlby analyzes the impact of attachment, separation, and loss. He focused on the critical role of the bond between mother and infant in emotional development.
Among his numerous works perhaps the most famous are:
Attachment. Paperback - 448 pages. 2nd edition (January 2000) Basic Books; ISBN: 0-46500-543-8.
Loss: Sadness and Depression (Attachment and Loss) Paperback - 496 pages. Reprint edition Volume 3 (January 2000) Basic Books; ISBN: 0-46504-238-4.
The Making and Breaking of Affectional Bonds Paperback (November 1979) Routledge Kegan & Paul; ISBN: 0-41504-326-3.
A secure Base: Parent-Child Attachment and Healthy Human Development. Paperback Reprint edition (August 1990) Basic Books (Short Disc); ISBN: 0-46507-597-5.
Interestingly, Bowlby also wrote a biography of Darwin: Charles Darwin: A New Life. Paperback (October 1992) W.W. Norton & Company; ISBN: 0-39330-930-4.