Warfare shaping human evolution?

Have a look at this article relating to warfare and how it has shaped humans today! It seems that it developed as a result of human culture. There also seems to be some unanimity relating to this subject by anthropologists, archeologists, primatologists and psychologists. Could this be the result of cooperation and the ability to work towards a common goal?

http://www.newscientist.com/article/mg20026823.800-how-warfare-shaped-human-evolution.html

To test my idea I have decided to complete research of free ranging white-faced capuchins and whether they show evidence of laterality (handedness). In humans it is thought that right-handedness is dominant due to the development of language, or due to the the ability to manipulate objects requiring complex motor skills (throwing theory). There have been a multitude of experiments on both new (eg capuchins) and old world monkeys (eg chimps) showing mixed results. My idea is that there may be some propensity for handedness in the wild if given the right environmental conditions. So for those capuchin monkeys who are forced by pressures in their environment to use more manipulative skills - handedness will be apparent. Sounds easier than it actually is.... because only few instances of tool use have been observed in the wild (eg nut cracking, oyster eating, crab eating).

So my goal is to try and find instances of tool use in wild capuchins in Costa Rica! Pity I can't do a comparison of two populations in differing habitats as I think this will have a bearing on my results. See what we come up with!