es3217w1

ES3217: The Loss of Childhood

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last updated 26.09.11.

Introduction

As we have seen, the historical trail leads to the conclusion that in Western culture, science in general, and human biology in particular, have inter-reacted with the rest of culture in profound ways. In each of the Western societies, the differential progress of these popultions through time and space have led to differing senses of national identity, tradition, and social preoccupations. To give but one example, the different reactions in Britain and the U.S. to abortion on demand. To put the matter simply, family life has become the site - not just of arguments about the making and maintenance of persons, but in addition, it has become a testing ground for working out the social, moral, and political meanings of the latest biological and psychological 'facts'.

The single book which I would ask you to consider puchasing for the first half of this module is Blaffer-Hrdy's Mother Nature. It is well written, and attempts to deal with these social dimensions while staying firmly within the 'Church of Science', to use a phrase of T. H. Huxley's. Hrdy's perspective is that of a biologist interested in the lives of primates as a principal source of evidence, but she also uses anthropology and makes a few references to paleo-anthropology - the study of prehistoric human groups. In order to immediately introduce you to the way in which she theorises about early childhood we start with a a sketch of some of the most important steps in her analysis of lactation - key concepts are in bold italic.

Lactation.

	Background Concepts
1	Principal background concept: the variable environments of evolutionary relevance: our form and nature has been formed over millions of years of primate evolution and has had to respond to multiple survival threats posed by various environments; this process is on-going.
2	John Bowlby's initial insight in the 1930's: *environments of evolutionary adaptedness (EEA)*. Bowlby attempted to characterise the lives of our Pleistocene progenitors as a means to say something general about the nature of motherhood, childhood, and family life. He also speculated that the closest approximation to our Pleistocene origin could be obtained by studying the life of contemporary hunter-gatherers. His main contribution was the perception that for an infant, the principal environment for evolutionary adaptedness was the mother herself.
3	Expanding the EEA: Bowlby's speculation has generally been found to be insightful and useful - many of Hrdy's own observations are based on evidence from contemporary hunter-gatherers, such as the !Kung.
4	However, the !Kung should be understood as representing one extreme in which there are extended birth intervals, with frequent suckling just to avoid dehydration, and infant survival depending on nursing extending into the fourth year. As Hrdy makes clear, present anthropological knowledge has established that even within the general survival strategy of hunter-gathering, there are many variations.
5	Present day humans should therefore be understood as an amalgam of responses to past selection pressures. Note that an amalgam is NOT the same thing as a completely new thing made out of a combination of parts - the word implies that the components are mixed together, may not be capable of forming a collective unity, and may tend to work against each other as separate entities in certain circumstances.
6	Hrdy uses the fantasy of the PPB - the perfect Pleistocene baby - to construct a contrast between what form human nature should have had if it had been constructed from scratch to meet the survival pressures of the Pleistocene, and what we actually had to hand to fight these same survival pressures.
7	Evolution since the Pleistocene has continued, and Hrdy draws especial attention to the consequences of moving to agrarian forms of subsistence and living in greater numbers and in closer proximity to one another: adaptations enabling some adults to digest milk, for instance, resistance to typhoid and malaria, and the possibility of developing resistance to HIV emerging.
	Lactation as a biological and social phenomenon
8	Balancing motherhood and work, Hrdy concludes, has perhaps never been harder than in contemporary societies based on the Western model of nuclear families as independent financial units. The reason for this is the enforced separation of women's productive capacity (work in factories and offices) from their reproductive capacity - children forced to stay away from such institutions, etc.
9	The concept of *allomothers* is introduced very early on in Hrdy's presentation. This is the notion of other adults, or semi-adults, capable of taking on some part of the burden of nurture temporarily, freeing the mother to carry out other tasks and functions.
10	What is lactation about? A sex-specific form of caretaking restricted to female mammals, with one exception, according to Hrdy. It evolved because it beat available alternatives, allowing mothers to both continue nurturing while not becoming unduly encumbered by the problems of storing the baby within her body - Hrdy suggests that in its basic form it allowed babies to be left temporarily while foraging could take place.
11	The merits of lactation: maternal provisioning through lactation spares immature forms the hazards of foraging and competing with more mature forms. (N.B. compared to other mammals, the human infant is effectively born some eighteen months premature.) It also buffers the infant from local scarcities, provides for a relatively stable immediate environment - the mother - and allows the mature physiology of the mother to convert a wide variety of foodstuffs into a form of nutrition that does not require a developed gut to handle it. Hrdy also points to the fact that once this adaptation had evolved, it conferred the potential for the animals possessing it to gain environmental flexibility: an animal evolving in the tropics could adapt to colder climates.
12	Storing fat, along with proteins and minerals, in parts of the body not likely to impede mobility unless stored in excess (almost impossible in a natural setting) is integrated with a development sequence: fat stores having reached a certain level some begin to secrete a hormone - leptin - which triggers the onset of an endocrinological cascade leading to menarche, shortly followed by full sexual fertility. In other words, *pregnancy only becomes possible once sufficient fat has been stored in the body to sustain an embryo through to full-term and to the lactation that follows*.
13	Details of lactation are closely linked to biological lifestyles. Animals dependent on extensive foraging to sustain their own survival typically produce highly nutritious and concentrated breast milk to sustain their young for extended periods while they are away. By comparison, human milk is relatively watery, containing diluted quantities of fat, protein, although relatively high levels of sugar; this implies its nature evolved in an EEA offering almost constant access. The intensity of suckling adjusts supply to meet demand, although many mammalian mothers adjust their infants birth weight to match their own level of physiological preparedness. Typically the healthier the mother the larger the baby and the greater and more immediate the lactation demand.
14	Prolactin is the hormone which promotes lactation itself, and Hrdy suggests it may have played a principal role in the evolution of lactation, since it is ubiquitous and could as easily be termed the 'stress' hormone, or the 'parenting' hormone. However, it is a hormone which also exists in fish, amphibians, and reptiles, where it is typically involved in maturation processes of one sort or another. In general, and across species, the higher the level of prolactin in both males and females, the more attentive the animal is to infant needs.
15	At the cellular level, the breast is equivalent to a pharmacy. In discussing the evolution of lactation in the monotremes (e.g. the duck-billed platypus), Hrdy identifies the probability that adapted secretions from sweat glands probably initially evolved to bathe the eggs within the burrow in an anti-bacterial and anti-fungal slime which conferred increased survivability. Subsequently, combining this with a nutritional boost would have further enhanced survivability. The final part of this bit of detective work is to suggest that colostrum, or 'first-milk' is the closest analogue humans produce to this form of secretion and it serves a related function in priming the infant's immune system. Although its nature changes after the first few days, human milk, like the milk of all mammals, continues to contain antibodies that the mother develops in her own body in relation to the infections her own infant is undergoing, thus allowing for the infant's own immune system to have time to develop.
16	Oxytocin: this hormone - the 'peace and bonding' hormone - is produced during birth and lactation. At birth it initiates the contractions of the uterus, and during lactation some of it enters into the milk being supplied to the infant and acts as a mild sedative. The hormone itself is specific to mammals. See the very clear diagram in Hrdy's book and the extended account of its actions.
17	Lactation, destiny, and social intelligence. Hrdy offers a contemporary socio-biological explanation for the evolution of social intelligence which comes in three steps: lactation is a caretaking provision linked to one sex; lactation increases the unavailability of females to male competition for successful mating; lactation prolongs the physical intimacy between infant and mother, and this entails increased levels of sociability.

Conclusion

There are two conclusions which I think should be kept in mind, although both of them are related to the Darwinian idea of an animal's nature being unintelligible unless it is considered in relation to its environment - and both the animal and the environment(s) have histories and futures.

The first conclusion which must be obvious from Hrdy's presentation is the extraordinarily close inter-relationship between aspects of human physiology and the survival of both mother and infant. Hrdy's presentation is largely conducted at the level of anthropological study, although there are some aspects of hormonal physiology introduced. In terms of its general appreciation, all of this complex adaptation aims to ensure the survivability of the infant, and this is matched by a corresponding level of complexity at the cellular and genetic level. (And usually, when problems do occur, they have their origin here.)

The second conclusion is one suggested in the introduction. You should consider Hrdy's presentation of lactation as a test case (and also an illustration) of her general thesis about the close involvement of physiological features of mammalian and primate infancy and birth with observable aspects of social behaviour - certainly - but also of covert aspects. Hrdy makes much of the fact that while a mother can be certain that a child is her own, at least within natural birthing situations, a father can never have that degree of certainty, and that as a consequence of this (and the fact that fathers do not give birth), there are marked behavioural differences between males and females, i.e., Hrdy's notion of what might be meant by the 'equality of the sexes' is well worth speculating about because of her emphasis on the biological constraints and opportunities unequally shared between the sexes.