Life History Balance (After Lovejoy 1981:343) His argument about bipedalism is that by gathering and collecting food items for their female partners, male hominids would be better able to improve their kin selection. Unlike Hewes and Isaacs, Lovejoy suggests that the food would comprise eggs, small amphibians and reptiles, nuts and fatty fruits as possible food sources rather than animal carcasses (pers. Comm. 2003.) Lovejoy asserts that in order for female hominids to maximise their reproductive potential, one of their few options open to them was to enlist a resource that few other primates use, but that is commonly used in other orders (e.g. canids and aves (p345)) – that is the utilisation of a male food provider. Following on from this is the logic that bipedal locomotion would maximise the transportation of such food items. The model assumes that sexual pairing was already prevalent at this time and Lovejoy is quite explicit, although speculative, in proposing that early bipedal hominids such as Australopithecus afarensis were basically monogamous. (p345) However, the reliance of the provisioning model on monogamy is problematic as there is little evidence in the fossil record for it. Indeed the consensus view of A. afarensis has been that it exhibited a fairly large degree of sexual dimorphism indicating, if anything, a very different sexual social system (see, e.g. McHenry 1991). Analysis of sex ratio evidence suggests that australopithecine male-female numbers were unequal, another counter indicator of monogamy (Reno et al 2003).Carrying food as a model for early adopters of bipedalism has another general problem, however: It makes already terrestrially vulnerable hominids even more vulnerable to attack from predators. If walking alone through open woodland is dangerous, how much more dangerous would it be to do so with both arms loaded with food items?
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However, Lovejoy appears to overlook a couple of key factors which would alter the results of this table significantly. •The human menopause was not considered. Lovejoy’s equation assumed that females potentially could continue to give birth at the same inter-birth interval until the age of 60. If realistic figures for menopause were used instead, survivability levels even closer to 1.0 would be needed to give Homo the same advantage. •The mothering ability was not offered as a factor in the 1981 paper. Lovejoy reports that even in apes the success of raising a first infant is much worse than later infants. The presence of elder females around, especially grandmothers who have passed into the menopause, would be likely to give humans an edge in this area over other species. Perhaps this was the main point Lovejoy should have been making. Generally, even accepting the basic argument that a more ‘k selected’ species would be able to out-compete the old world monkeys, it is not clear that the provisioning model provides that selection, either through improved mothering (infant carrying) or through paternal provisioning. In terms of the survivability Lovejoy’s thesis relies upon, it seems unlikely that bipedal carrying of small infants is any safer, for a terrestrial primate, than quadrupedal clinging.