 Adaptationism (Failure to adequately consider causes of evolution other than natural selection). Causes of evolution other than natural selection must be tested. For example, even if there are behaviors that are correlated with specific genes it does not follow that the behavior is the result of natural selection and hence is an adaptation. Genes commonly have multiple effects and it is possible for natural selection to select for only one of those effects. In this case the other effect will increase in frequency in the population even though it is not selected for. A similar case can occur when two genes are linked on the same chromosome. In this way a behavior may be very common not because it confers an evolutionary advantage, but because it is associated with a different beneficial trait. Other causes of evolution include random drift, mutation, and immigration of individuals between populations. Recall that Elisabeth Lloyd (2003) identified adaptationism as a problem with Thornhill and Palmer's arguments about the evolution of rape.