Matteo Mameli

(2) There is significant cultural variation in the way people reason, categorize, and react to various aspects of the world. A proper understanding of such variation has implications for theories about human nature – and cognitive architecture – and its malleability. In turn, these theories have implications for theories about the status and generalisability of psychological explanations (see Nisbett 2003), for theories about the extent to which social engineering and social reform is possible (see Singer 2000), etc.

Cultural traits are those phenotypic traits whose development depends on social learning. These include practices, skills, beliefs, desires, values, and artefacts. The distribution of cultural traits in the human species changes over time. But this is not enough to show that culture evolves. That depends on the mechanisms of change. In the cultural realm, one can often observe something similar to biology’s ‘descent with modification’: cultural traits are sometimes modified, their modifications are sometimes retained and passed on to others through social learning, until new modifications are added. In this way, new modifications are piled on top of old modifications, generating cumulative change. But, again, this is not enough to show that culture evolves. For culture to evolve, cumulative change must be the result of hidden-hand mechanisms similar to those that explain cumulative biological change. If cumulative cultural change cannot be explained in these terms, the analogy between cultural change and biological evolution is unhelpful. The best known biological mechanism is natural selection. There are reasons to think that cultural change is at least sometimes due to natural-selection-like mechanisms. The adaptive fit often found between cultural traits and the environment has in many cases been built gradually and in a way that involves natural selection operating at the cultural level. The parallel with morphological adaptation is compelling. No complete and universally accepted account of natural-selectionlike processes operating at the cultural level exists at this stage. But at least three kinds of processes seem possible.

A recent study by Castellani et al. (JAMA 302(23):2573–2579, 2009) describes the population-level effects of the choices of individuals who underwent molecular carrier screening for cystic fibrosis (CF) in Veneto, in the northeastern part of Italy, between 1993 and 2007. We discuss some of the ethical issues raised by the policies and individual choices that are the subject of this study. In particular, (1) we discuss the ethical issues raised by the acquisition of genetic information through antenatal carrier testing; (2) we consider whether by choosing to procreate naturally these couples can harm the resulting child and/or other members of society, and what the moral implications of such harm would be; (3) we consider whether by choosing to avoid natural procreation carrier couples can harm current or future individuals affected by cystic fibrosis; (4) we discuss whether programs that make carrier testing available can be considered eugenic programs.