 Maclaurin and Sterelny contend that the fundamental unit of biodiversity is species and specifically species richness. Notoriously, biologists and philosophers have debated the nature of species. However, Maclaurin and Sterelny defend an evolutionary concept of species which states that “Evolutionary species are lineages of organisms with their ‘own evolutionary tendencies and historical fate’” (Maclaurin &amp; Sterelny 2008: 33; see Wiley 1978). They suggest that this is the more natural approach to species because,