Although there is substantial reason to believe that natural selection has directly equipped human beings with mechanisms that readily lead to individual violence, there is no evidence that warfare as such has been part of the biological bequeathal to us as hominids. On the contrary, there is abundant evidence that war is a comparatively recent cultural addition to the human repertoire, acquired within the last 10,000 years or so as a result of several factors, including the invention of agriculture – resulting in the accumulation of valuable material resources that lend themselves to being stolen as well as defended, along with enabling the construction of elaborate social hierarchies – plus increasingly effective technologies for communication, coordination and killing. (The evidence for the recent emergence of war is persuasively reviewed and summarized in War, Peace, and Human Nature: The Convergence of Evolutionary and Cultural Views (2013), edited by anthropologist Douglas P. Fry.)
The scientific finding that greed (under current social conditions) can stimulate feelings of pleasure similar to sex or drugs does help explain why capitalists seem to actually lust after profit and power, and why this lust will lead them to seek short-term gratification even if the long-term results of their action may be disastrous. The experiments by Knutson offer one explanation for corporate opposition to environmental controls, as the tycoons of oil industry and other capitalists risk global warming and the long-term destruction of human life on earth rather than give up even a portion of their current profits.