 Another nexus of topics in the philosophy of evolution involves  heredity and heritability.  Although it was not explicitly emphasized in the definitions of evolution given above, evolution is usually taken to be about heritable changes over time, i.e., characteristics that are able to be passed from one generation to the next. But there has been some discussion over which entities can properly be said to be heritable. Genes are uncontroversial, but are seen as too limited by some, who would consider phenomena such as learning and cultural transmission, epigenetic inheritance, and ecological inheritance to be heritable as well. The term “heritability” can likewise cause confusion, as it is a technical term within evolutionary theory, and understanding the term and its implications is not trivial. Classically, heredity has been thought of in terms of the  genotype/phenotype distinction,  with genotypes being seen as heritable and phenotypes being seen as not heritable. But to accept that distinction seems to accept a distinction between  innate and acquired characteristics,  and that distinction has been challenged, or at least shown to be more complicated than it would seem at first glance. Heredity also raises questions about  biological information—do  genotypes pass along information, and if so, in what sense?