Doctor of Philosophy

dissertationIn this dissertation, I follow three avenues of inquiry regarding status competition among the Bardi - a group of part-time foragers living in northwestern Australia. The first focuses on how the current array of status-linked behaviors came to be so widely used. After a brief introduction, I present findings from a year-long ethnographic study of Bardi men. I review the recent, postcontact history of the region with special emphasis on venues of status competition. Relying upon comparative and historical evidence as well as theoretical inferences, I detail how two novel status-linked behaviors (i.e., wage labor and dealing with bureaucracy) emerged in the latter half of the twentieth century as well as the effects of religious and governmental interventions on more traditional activities such as big game hunting and gaining cultural knowledge. Describing how these options emerged provides key insights into the contemporary competitive environment in Bardi country, but a comprehensive picture of male competition there requires a sense of how men make use of these behaviors. The third chapter therefore engages the observation that men have many more options for seeking status when compared to other primate males, yet we know relatively little about how men cope with the sometimes-overwhelming array of opportunities. Focusing on whether men constrain their efforts to just a few behaviors or whether they make use of every available opportunity, I find that the most prominent men are known for their success in most, if not all, domains of status competition. In the fourth chapter, my coauthors and I build upon lessons from the Bardi case in reviewing distinctive attributes of men's competitive behavior. We begin with the observation that, as compared to status seeking among other male primates, men rely less on within-group violence, make use of a wider range of behaviors, and readily incorporate new opportunities into their behavioral repertoire. Through a survey of relevant ethnographic, primatological, and experimental evidence, we tie these characteristics to the uniquely human aptitude for and interest in sharing mental states with others

Evaluation of kochia as a high yielding forage crop for saline soils

Non-Peer ReviewedForage dry matter yields of up to 11,670 kg/ha, at a soil conductivity of 12 ms/cm, were measured in three years of trials at several saline sites in Saskatchewan. Feed values were comparable to common hays, based on in vitro analyses and a digestibility and intake trial done with sheep. Salt accumulation in kochia forage was higher than other forages but was calculated to be not significant in saline soil reclamation. Potassium was the major cation accumulated by kochia forage even though the saline soils were high in soluble sodium and magnesium cations. A Texas accession gave a much higher forage yield in a greenhouse trial than a Saskatchewan selection, and did not set seed in greenhouse and field trials. Further work is needed to turn this wild plant into a crop is discussed

Ovarian follicle loss in humans and mice: lessons from statistical model comparison

journal articleMenopause is triggered by the number of ovarian follicles falling below a threshold number and is irreversible because oogonial stem cells disappear after birth. Since it is the result of programmed disappearance of a limited store of follicles, menopause can be predicted using mathematical models based on total follicle counts at different ages. Our model shows follicle numbers decline bi-exponentially rather than as a simple exponential function of age, as had been assumed, with a first exponential rate parameter of −0.097 and a second of −0.237. The change occurred when numbers had fallen to the critical figure of 25 000 at age 37.5 years. The unexpectedly faster rate of ovarian ageing afterwards lowers the follicle population to 1000 at ∼51 years, and was adopted as the menopausal threshold because it corresponds to the median age of menopause in the general population. Had the earlier rate persisted menopause would not be expected until 71 years. The impact of step reductions of follicle numbers on the prospective span of menstrual life was predicted by the model. A reduction by 50% before age 30 years resulted in the threshold being reached at 44 years and 0.6 year later for every subsequent year until age 37.5 years after which it is reached at 48 years. A reduction of 90% in childhood before age 14 years could result in menopause as early as 27 years, with increments of 0.6 year per year afterwards until after 37.5 years when it is expected at age 41 years. The predictions are reassuring insofar as they confirm anecdotal evidence that long-term ovarian function is not substantially comprised by reducing as much as one-half of the mass

Grandmothers and the evolution of human longevity: a review of findings and future directions

journal articleWomen and female great apes both continue giving birth into their forties, but not beyond. However humans live much longer than other apes do.[1] Even in hunting and gathering societies, where the mortality rate is high, adult life spans average twice those of chimpanzees, which become decrepit during their fertile years and rarely survive them.[2, 3] Since women usually remain healthy through and beyond childbearing age, human communities include substantial proportions of economically productive postmenopausal women.[4-7] A grandmother hypothesis8-12 may explain why greater longevity evolved in our lineage while female fertility still ends at ancestral ages. This hypothesis has implications for the evolution of a wide array of human features. Here we review some history of the hypothesis, recent findings, and questions for ongoing research

A bioenergy success story: the energy savings implications of the increase in legumes in rotations since 1990

Non-Peer ReviewedThe energy savings achieved by the increase in field peas and lentil production in western Canada between 1990 and 1995 were calculated to be 4.46 PJ (petajoules) per year, equivalent to 1.7 % of the total energy costs of agriculture production in Alberta, Saskatchewan and Manitoba, and equivalent to 7.5 % of 1990 nitrogen fertilizer use. A modem ethanol-from-grain industry would have had to produce 380 million litres of ethanol to achieve the same net energy gain. The increase in soybean production hectares in Ontario since 1990 was calculated to be saving 3.92 PJ per year, equivalent to an ethanol industry of 330 million litres. The combined energy savings from these legumes in rotations in Ontario and western Canada were calculated to be 8.38 PJ, equivalent to an ethanol industry of 710 million litres. This is much larger than the existing 31 million L/year Canadian fuel ethanol industry, and equivalent to 17.7 % of present U.S. ethanol production. In addition, the energy costs of producing grain crops after a legume in the rotation were reduced. These reductions in energy costs of grain production would also reduce the overall energy costs of ethanol production