 By applying these sorts of considerations to the cultural realm we can attempt to understand the likely costs and benefits associated with various different forms of cultural inheritance (vertical, oblique, meme-like and so forth). We can also perhaps come to an understanding of the different evolutionary forces that might bring these different forms of cultural inheritance into existence. And, in turn, these insights may facilitate comparative work that seeks to document the general conditions that are required for a species to make use of cultural inheritance in order to build complex adaptations such as tools. This way of thinking offers the promise, for example, of explaining why few, if any, non-human species are able to build progressively more and more complex cultural features in a cumulative manner (Richerson and Boyd 2005, 107; see also Laland 2017). The exploration of the significance of these conditions in the cultural realm is contentious, partly because the conditions for evolvability themselves are disputed (see Godfrey-Smith 2009). Boyd and Henrich’s work brings out the fact that although population-level inheritance is important for adaptation, parent-offspring resemblance is not, in fact, necessary. Questions relating to evolvability are also tied up with difficult issues relating to the units-of-selection debate (Okasha 2006). As we have seen, natural selection at a higher level of organisation may be required to generate mechanisms that suppress the ability of disruptive ‘outlaws’ to go it alone at lower levels of organisation. Does something like this occur in the cultural realm? Does selection on human groups act so as to limit the ability of individual humans to go it alone? In what ways might cultural inheritance be involved in these processes? These questions are complex, both in terms of how they should be posed and how they should be answered. But some of the most interesting work in cultural evolutionary theory may come from efforts to answer them.