Human Evolution de Robin Dunbar
The way ahead
[...]The approach that I will adopt here is very different. It exploits our much improved understanding of how primates allocate time to the various core activities (feeding, travel, rest, social bonding) that are crucial to their ability to survive in a particular habitat. This approach builds on a series of time budget models that we have developed for a number of monkey and ape species – models that allow us to predict exactly how much time an animal should devote to each of these core activities in a particular habitat. The key issue here is that the length of the working day is limited (we all sleep at night) and all these core activities have to be performed within the waking day. The fact that we are dealing with a biological system here is a crucial advantage: in biological systems, changes in one component cannot happen without having knock-on consequences elsewhere in the system. A species cannot increase its brain or body size without affecting the time it has to spend feeding, and it cannot change its feeding time allocation without affecting the time available for other equally crucial activities like travel or socializing. In a word, the numbers have to add up. And this gives us a powerful tool for exploring species’ responses to changing circumstances.