 Paul Griffiths (2002) has clarified what is ontologically at stake in this objection to nativism. Researchers who draw questionable inferences about the properties associated with innateness are assuming (implicitly, if not explicitly) that innateness is a natural kind. More specifically, they assume that innate traits form what Robert Boyd (1989) called a homeostatic property cluster. Such property clusters require the existence of some causal process that “holds together” the relevant properties in a coherent bundle, so to speak. For example, Weismann assumed that the only way for a trait to be modified by natural selection is if it develops “directly” from germline cells. He also assumed that germline cells were the only possible source of developmental stability since environmental factors were seen exclusively as a source of developmental noise (Johnston 1995). Thus, on Weismann’s picture, the properties of being an adaptation and being developmentally stable were a part of the same homeostatic cluster. It turns out that Weismann’s picture of development was too narrow. The environment is much more than just a source of noise. Certain environmental factors are a source of developmental stability (West-Eberhard 2003), acting as a “scaffold” for the development of particular traits (Sterelny 2003). The environment can also store information that organisms rely on during development to generate adaptive phenotypes (Mameli 2004). So, contra Weismann, there is no distinct causal process associated with germline cells that accounts for developmental stability and adaptation. Without a known process to unify the various properties associated with innateness, Griffiths (2002) argues, the assumption that they form a homeostatic cluster is unwarranted.