 These theoretical considerations were soon followed by field examinations of drift (there were also laboratory studies, but these were less contentious). Two sets of studies of natural populations are particularly notable. One set, referred to in the introduction to this essay, is composed of the studies of the polymorphic land snail, Cepaea nemoralis; these studies, and debates over the prevalence of drift, began in the 1930s and became quite heated in “The Great Snail Debate” of the 1950s and 1960s (Millstein 2008, 2009 gives more extensive discussion, from which the following is drawn; the moniker “The Great Snail Debate” is due to Provine 1986). Early researchers, most famously Arthur J. Cain and Philip M. Sheppard (1950, 1954), sought to demonstrate the adaptedness of the color and banding morphs of the snails as well as the sizes of the populations in which they lived. But these were challenging to determine; adaptedness was primarily studied indirectly, by seeking correlations between variants and their backgrounds (presuming camouflage and selection by predator), and population sizes varied considerably. And any correlations found were statistical ones, with lots of “noise”. This left the door open for drift; Maxime Lamotte (1959) argued that by examining the populations as a whole, one found greater variation among the small populations than among the large. This was a distinctive signature for drift, but such outcomes are hard to find and require a very special set of circumstances to obtain (large numbers of populations of varying sizes that are easy to count). However, Lamotte’s study is not the only classic evolutionary study to exploit this unique drift outcome; Cavalli-Sforza’s studies of blood groups in humans did so as well (Richardson 2006). Notably, this was not drift as an alternative to selection (Cain and Sheppard had suggested that selection precluded much of a role for drift), but rather, an argument for a substantial role for drift in addition to a substantial role for selection.