 Philosophers interested in explanation have recently turned their attention to mechanisms: “mechanisms are sought to explain how a phenomenon comes about or how some significant process works” (Machamer, Darden, &amp; Craver 2000: 2). One way to secure explanatory status for selection would be to show that it functions as a mechanism. Whether natural selection qualifies as a mechanism is controversial. Skipper and Millstein gainsay the position: natural selection not organized in the right sort of way to count as a mechanism, exhibits a lack of productive continuity between stages, and further lacks the requisite sort regularity of operation (Skipper &amp; Millstein 2005: 335). Barros (2008) has argued that natural selection may be characterized as a two-level mechanism, with a population-level mechanism and an individual-level mechanism working together. Havstad (2011) responds that the account Barros offers is too general and so includes any selective process, not just natural selection. Moreover, the parts/entities and activities/interactions that supposedly make-up the mechanism of selection can only be specified by the roles in the selective process, whereas mechanistic explanation works by associating these roles with specific phenomena (Havstad 2011: 522–523). Matthews (2016) offers a case study of the debate over selection as a mechanism, while DesAutels (2016) provides a defense of a mechanistic view.