Nicholas G. Blurton Jones

Hadza Hunting, Butchering, and Bone Transport and Their Archaeological Implications

A study of Hadza hunting and scavenging practices, patterns of medium/large mammal carcass dismemberment and transport from kill sites to base camps, and subsequent processing and disposal of bones reveals archaeological bone assemblage formation processes among these hunter-gatherers in northern Tanzania. Body part transport patterns are highly variable, but they probably are understandable in terms of the goal of maximizing net nutritional benefit relative to the costs of field processing and transport. The Hadza data have implications for some widely held views about patterns of bone transport among hunters, for particular reconstructions of past human or hominid behavior based on those views, for the problem of distinguishing hunting versus scavenging as contributors to assemblage composition, and for current thought about the suitability of modern hunters as a source of inference about the prehistoric past.

Women's Reproductive Cancers in Evolutionary Context

Reproductive experiences for women in todays affluent Western nations differ from those of women in hunting and gathering societies, who continue the ancestral human pattern. These differences parallel commonly accepted reproductive risk factors for cancers of the breast, endometrium and ovary. Nutritional practices, exercise requirements, and body composition are nonreproductive influences that have been proposed as additional factors affecting the incidence of womens cancers. In each case, these would further increase risk for women in industrialized countries relative to forager women. Lifestyles and reproductive patterns new from an evolutionary perspective may promote womens cancer. Calculations based on a theoretical model suggest that, to age 60, modern Western women have a breast cancer risk as much as 100 times that of preagricultural women.

Bushman birth spacing: A test for optimal interbirth intervals

Abstract Long interbirth intervals (IBIs) are reported by Lee and by Howell for !kung women, averaging around 4 years between births. Is this low rate of births maladaptive? An earlier analysis of the ecological constraints upon !kung women suggested that it might not be. Given the observed features of !kung ecology, shorter IBIs require a mother to carry much greater loads (backload) of baby and food on her foraging trips. Calculating this load for each IBI shows a sharp upturn in backload when IBIs fall below 4 years. It was suggested that sharply increased backload might lead to such a severe increase in mortality of offspring that the observed 4-year IBI actually maximized the number of offspring that the woman raised. This proposition is tested in this article using reproductive histories of individual !kung women collected by Howell. Backload calculated in the previous study is the best predictor of the observed losses of children at each IBI. Furthermore, mortality of the children is indeed so sharply related to IBI that the 4-year IBI appears to be the interval that maximizes reproductive success for most women.

Foraging Returns of !Kung Adults and Children: Why Didn't !Kung Children Forage?

Children of the hunting and gathering !Kung San seldom foraged, especially during the long dry season. In contrast, children of Hadza foragers in Tanzania often forage, in both wet and dry seasons. Because we have argued that the economic dependence of !Kung children has important consequences, we must try to understand why they did not forage. Experimental data on foraging by !Kung adults and children show that children would have had to walk far from dry season camps to acquire much food. Interviews suggest that !Kung children risk getting lost if they wander unsupervised into the bush. Thus, foraging without adult company was a poor option for !Kung children. Foraging with adults might have been a better strategy. We calculate the benefits to a !Kung mother if her oldest child accompanied her to the nut groves. Because of the high processing costs, a childs work time was most profitably spent at home cracking nuts.

Bushman birth spacing: Direct tests of some simple predictions

Abstract Blurton Jones and Sibly (1978) developed a model of costs (weight of food and baby carried while foraging) of !Kung womens reproduction under ecological-economic constraints that were described by Lee (1972). Predictions are drawn from this model and tested on Howells (1979) data from reproductive histories of 172 individual women. Women were rated on a scale of dependence on bush or cattlepost foods. The ratings were compared with what is known about the places at which the women gave birth to their children. Agreement was good and the population was divided into two groups for study: 65 women most dependent on bush foods and 70 women substantially dependent on agricultural produce. Thirty-seven women of uncertain or intermediate status were omitted. As predicted by the model, among the women who were dependent on bush foods: (1) first interbirth intervals (IBI) were shorter than were later IBI; (2) the survivorship of children in first IBIs was not strongly related to length of IBI, with shorter IBI giving as good survivorship as longer IBI; (3) IBIs lengthen as the number of surviving children increases, until the fourth child; (4) after the fourth child IBIs do not differ significantly although they tend to be shorter (contrary to the prediction, a null hypothesis whose statistical support is consequently poor); (5) for IBIs after the first IBI, mortality increased markedly as IBI decreased; (6) mortality was even more closely related to backloads entailed by each IBI, as calculated by Blurton Jones and Sibly (1978); (7) mortality was less closely related to backloads calculated from an alternative version of the model from which weight of food was excluded; (8) as reported by Howell (1979), a new pregnancy followed rapidly after the death of the preceeding child but (9) as predicted, a new pregnancy did not follow so fast after the death of older children; (10) for the cattlepost women IBIs were shorter than for women dependent mainly on bush foods; and (11) there was no significant relationship between IBI and mortality for the cattlepost women, and mortality at short IBI was lower than in bush women. The assumption that the benefit accruing from more births will be balanced against the costs (costs to survivorship assumed to result from the work entailed by caring for each child) was successful in giving many predictions confirmed by the data. The significance and limitations of this “optimization” study are discussed.

Distribution of Refuse-Producing Activities at Hadza Residential Base Camps

Recent research on prehistoric hunter-gatherer site structure continues to be concerned primarily with the identification of discrete, activity-specific areas within sites (e.g., Carr 1984; Hietala 1984; Flannery 1986). However, an increasingly large body of ethnoarchaeological data suggests that such areas may be rare in the archaeological record, especially among middle- and low-latitude foragers (Yellen 1977; O’Connell 1987). Here we present additional data pertinent to this topic, derived from recent fieldwork among the Hadza of northern Tanzania. Preliminary analysis indicates that although activity areas can be identified within Hadza base camps, the range of activities associated with each are broad and broadly similar from area to area. Assumptions commonly made by archaeologists about the differential distribution of activities are only weakly supported by our data.

A suggested adaptive value of toddler night waking: Delaying the birth of the next sibling

Abstract In industrial societies around 20% of children aged 1 to 3 years wake at night and cry enough to wake their parents. We suggest that instead of regarding this common behavior as pathological we might consider whether it is, or could once have been, an adaptive response. We suggest that one outcome of this behavior, plausibly adaptive, would be delaying the conception of the next sibling. This could happen if night wakers would, given the chance, suckle more often at night than nonworkers, which in turn would delay the return of ovulation. The delay would be of greater advantage to vulnerable children whose survivorship would be most threatened by the arrival of the next sibling. This suggestion is compared to the view that sleeping apart from parents is an abnormal situation to which we cannot expect all children to adapt.

More Lessons from the Hadza about Men’s Work

Unlike other primate males, men invest substantial effort in producing food that is consumed by others. The Hunting Hypothesis proposes this pattern evolved in early Homo when ancestral mothers began relying on their mates’ hunting to provision dependent offspring. Evidence for this idea comes from hunter-gatherer ethnography, but data we collected in the 1980s among East African Hadza do not support it. There, men targeted big game to the near exclusion of other prey even though they were rarely successful and most of the meat went to others, at significant opportunity cost to their own families. Based on Hadza data collected more recently, Wood and Marlowe contest our position, affirming the standard view of men’s foraging as family provisioning. Here we compare the two studies, identify similarities, and show that emphasis on big game results in collective benefits that would not be supplied if men foraged mainly to provision their own households. Male status competition remains a likely explanation for Hadza focus on big game, with implications for hypotheses about the deeper past.

Workshop report: Evolutionary life history analysis of human behavior

On 21 May 1983 a workshop was held at the University of California at Los Angeles on the application of evolutionary life history models to the study of human behavior. There were 24 attendees, representing primarily the academic disciplines of anthropology, biology. and psychology. The major purpose of this workshop was to discuss the applicability of evolutionary life history models to the study of human reproduction and development, with a major emphasis on developing research methodology. There were nine presentations. [Abstracts of the papers presented at the workshop have been published previously in the HI/~~c~H Etholog\ Nm.s/rttcr. (vol. 3. no. IO: 1983). and are available from the authors upon request.] In his introductory comments. Konald Weigel addressed

Towards hypothetico‐deductive anthropology?

Winterhalder, Bruce, and Eric Alden Smith, eds. Hunter‐Gatherer Foraging Strategies: Ethnographic and Archaeological Analyses. Chicago: University of Chicago Press, 1982. x + 268 pp. including bibliography and index.