 with proposed numbers including 1/4, 1/2, and 1; in between values are thought to be where the two causes are more or less equal (Clatterbuck, Sober, and Lewontin 2013). Clatterbuck, Sober, and Lewontin point out that on the standard picture, the values of N and s do not predict one gene frequency outcome; rather, they predict a probability distribution of possible gene frequency outcomes. But, they argue, you can change this distribution by changing N or by changing s, with values “chosen so that the first change makes more of a difference, or less, or the same, as you please”; thus, it is “arbitrary to focus on comparisons that give drift the upper hand, or that do the same for selection” (Clatterbuck, Sober, and Lewontin 2013: 538). Here, the suggestion seems to be that N represents the drift cause and that s represents the selection cause—although it’s not clear why drift-as-cause should be equated with population-size-as-a-cause—with the conclusion that the causes are not separable. To say that they are separable would, Clatterbuck, Sober, and Lewontin say, would be akin to asking whether the result of four heads of a fair coin tossed ten times is due to the fairness of the coin or the number of tosses. They also suggest that it is impossible to have a population that is not undergoing drift, since even in an infinite population there could be deviation from selective expectations (again, making it hard to separate the causes). Finally, they argue that it doesn’t make sense to say that with identical setups that producing differing outcomes, that selection dominates in some (when the favored allele increases in frequency) and drift in others (when the favored allele decreases in frequency).