 What’s more, some philosophers have argued that it is possible for traits to be adaptations in the standard sense even when they are not heritable according to the population genetic  definition[7].  Despite the claim above that heritability in the population genetic sense is required as a condition of the action of natural selection, technically all that is required for natural selection to occur on a trait T is for T to be heritable in the weaker sense, i.e. that it be robustly transmitted, such that the trait variant in a parent tends to turn up reliably in the offspring. The reason heritability in the population genetic sense was believed to also be necessary for natural selection was that genes were believed to be the only developmental resource transmitted to offspring, so only if variation in traits followed variation in genes would traits be subject to natural selection for the reasons described above. However, recently a variety of philosophers and scientists have argued (Odling-Smee et al., 2003; Sterelny, 2003, 2007, 2012) that natural selection can occur on traits even if traits vary most with the environment rather than genes, so long as environments can themselves be transmitted down lineages; Sterelny’s suggestion is that this might be achieved by robust niche construction. This has an interesting consequence: if highly reliably transmitted cultural traits could be subject to natural selection, standard evolutionary methods and models of the sorts used in behavioral ecology could be used to understand the evolution of such traits.