Until a few generations ago, humans made their living by foraging, like other animals. We have therefore inherited genes that allowed our ancestors to thrive as hunters and gatherers. Thriving in a modern economy requires very different behaviours but we cope because the human brain evolved to be flexible with the ability to form cooperative networks with other humans and to maintain the shared body of information, expertise and values which we call "culture". We argue that human economic behaviour is influenced by both the genes and the culture that we "inherit" and that both are a result of a Darwinian evolutionary process. An evolutionary approach is therefore likely to be of value in developing theories of economic behaviour. We then use this approach to analyse in broad terms how people that are born with the brains of foragers living in a small-scale society become consumers in a modern society and where this behaviour is likely to lead our species.