The cultural group selection hypothesis
A new paper by Adrian V. Bell, Peter J. Richerson, and Richard McElreath published online in PNAS (doi: 10.1073/pnas.0903232106) entitled "Culture rather than genes provides greater scope for the evolution of large-scale human prosociality" (Restricted access) in which they argue that cultural group selection is much mores likely than genetic group selection to have promoted the evolution of altruistic and cooperative behaviours in humans. In essence: "What is the scope for group-level selection on cultural variation and how does this compare to the equivalent for genes? […] Despite good reasons to believe our estimates of cultural variation are underestimates, we find much greater scope for multilevel selection on human culture than on human genes."
Abstract: Whether competition among large groups played an important role in human social evolution is dependent on how variation, whether cultural or genetic, is maintained between groups. Comparisons between genetic and cultural differentiation between neighboring groups show how natural selection on large groups is more plausible on cultural rather than genetic variation.