 Another objection to adaptationist methods from Gould and Lewontin that has persisted as a criticism of behavioral ecology is that these methods do not allow scientists to consider non-adaptationist explanations for the traits to which they are applied, such as whether those traits were fixed by drift or are simply side effects of other traits (i.e. whether they are “spandrels”). In principle, correctly pursued, adaptationist methods can help identify cases where a trait is a non-adaptation: drift, for example, can be identified by comparing the distribution of traits expected under selection and under drift with actual population distributions (Sober, 2005); the question is whether the types of methods used in behavioral ecology are the most efficient at detecting these cases (Lewens, 2009). Some philosophers have argued that methodological adaptationism is more pernicious in practice than it looks in principle, because real evolutionary social scientists are not good at dropping adaptationist hypotheses for a trait even when there is a strong case to be made that they should (see, for example, Lloyd, 2005, esp. Chapter 8). For further discussion of all these problems, see the entry on  adaptationism.