Hunting and the Role of Men in Human Reproduction
Male behavior plays a distinctive role m human life histories in two ways. First, hunting, the primary subsistence activity of adult men,, is the most learning-intensive foraging strategy practiced by humans. Second, unlike most higher primates, men plav a major role in the energetics of human reproduction. We know of no ethnographers who successfully dig roots or crack nuts at the rate of members of their study populations. Indeed, the same patterns are seen among captive animals released into...
Box A Formal Model of Natural Selection on Age at First Reproduction and
The modei treats two phases of the ire course, the juvenile and ' adult periods. The juvenile period begins after the high mortality phase associated with infancy and weaning, is dedicated to growth and development, and lasts a variable amount of time, r. upon which selection acts. During this time, all energy is invested in either embodied capital growth and learning affecting future energy production, P, or in reducing mortality rate, 1. The two choice variables during the juvenile period are...
Reduction in Juvenile and Early Adult Mortality Rates
Human foragers have longer maximum life spans than chimpanzees do suggesting that they may have lower mortality rates over much of the life span tw 67 Both groups experience minimum mortality raies in the late juvenile and early adult period, a pat tern typical of many living organisms.68 However, the minimum mortality rate of foragers is about 1 per year, whereas the minimum rate for chimpanzees is about 3.5 per year Fig. 10 . We propose that the character of food resources taken by humans...
The Grandmother Hypothesis
The present theory shares some features with a model of menopause and human life history recently proposed by Hawkes and colleagues,530 often referred to as the grandmother hypothesis. This hypothesis proposes that humans have a long life span relative to that of the other primates because of the assistance that older postrepro-ductive women contribute to descendant kin through the provision of difficult-to-ac quire plant foods. Women, therefore, are selected to invest in maintaining their...
O
co r- O O O O o o - O O d o d o d Lf CO r CO - t gt lt gt . OOOr CNOO-OO diets is vertebrate meat. This ranges from about 30 to 80 of the diet in the sampled societies, with most diets consisting of more than 50 vertebrate meat equally weighted mean 60 . The emphasis on vertebrate meat would be even more clear it any high-latitvide foraging societies were included in the sample. In contrast, chimpanzees spend only about 2 of their feeding time eating meal. Unfortunately, the diet of wild...
DISCUSSION Primate LifeHistory Evolution
The life-history traits and large brains of fully modern Homo sapiens may be seen as the extreme manifestation of a process that defines the primate order as a whole. Our theory organizes the major evolutionary events in the primate order and the specific changes that occurred in the hominid line. The early evolution of the primate order 60 mya to 35 mya was characterized by small increases in enceph-alization. Relatively little is known about early life-history evolution except that it appears...
The Hominid Line
The fourth major grade shift in primate evolution occurred with divergence of the hominid line, particularly the evolution of genus Homo. The brain and life span of modern humans are clearly outliers compared to those of other mammals, and even as compared to the relatively large-brained, slow-living primates. The evolution of these extreme adaptations in the hominid line is built on a hominoid base that already showed a significant tendency toward large brains, long lives, and exploitation of...
References
1 C narnov EL. 1993. L le history invariants some explanations of symmetry in evolutionary ecology. Oxford Oxford University Press. 2 Gadgil M, Bosser WH. 1970. Life historical consequences of natural selection. Atn Nat 104 1-24. 3 Janson CH, Van Schaik CP 1993. Ecological risk aversion in juvenile primates slow and steady wins the race. In Pereira VI. Fairbanks L editors Juvenile primates life history, development and behavior. New York Oxtord University Press, p 5 -76. 4 Kozlowski J, Wiegert...