Logistical mobility reduces subsistence risk in hunting economies

Increasing carnivory is frequently cited as one of the key trajectories in the course of hominin evolution, yet the ethnographic record demonstrates that hunting is a high-variance, risky strategy necessitating a fundamental re-organisation of the foraging pattern. Hunter-gatherers rely on intra-band sharing of hunted resources as well as inter-band insurance mechanisms to mitigate against the risk of resource failure. It is suggested that logistical mobility functions to increase encounter rates with both prey and representatives of neighbouring groups, and is thus a fundamental part of the hunting adaptation. Implementation of an ideal gas model of encounter rate demonstrates that, when logistical mobility is regarded as a basic group fission pattern, it increases encounter rates for all groups relying on greater than 34% hunting. This equates to a shift in the optimal hunting percentage, as defined by encounter rates, from 24% under residential mobility to 35% under a logistical mobility strategy. These results are discussed in relation to fission-fusion social systems in primates and social carnivores, with a view to highlighting the specific aspects in which these differ from human foraging strategies. (C) 2010 Elsevier Ltd. All rights reserved.