Defining the genus Homo
The definition of the genus Homo is an important but under-researched topic. Inthis chapter we show that interpretations of Homo have changed greatly over thelast 150 years as a result of the incorporation of new fossil species, the discoveryof fossil evidence that changed our perceptions of its component species, andreassessments of the functional capabilities of species previously allocated toHomo . We also show that these changes have been made in an ad hoc fashion.Criteria for recognizing fossil specimens of Homo have been outlined on a number of occasions, but these criteria have generally not been explicitlyderived from a genus concept. Rather, the course of action followed by mostresearchers has been to assign new specimens to Homo on the basis of a subset ofthe diagnostic traits that are considered to be key, and to then redefine the othertraits of the genus in the light of the morphological and functional attributes of thenew specimens. With a view to moving beyond this approach, in the next sectionof the chapter we outline six competing proposals for how genera should bedefined, and consider their impact on the species assigned to the genus Homo .Subsequently, we consider the pros and cons of the six genus concepts. We arguethat three of them are impractical and/or internally inconsistent, and that three areuseful. We go on to suggest that, while there is little to choose between the latterthree concepts on theoretical grounds, the one put forward by Wood and Collard(Science 284: 65–71, 1999 ) has practical advantages. In the last part of the chapter,we update Wood and Collard’s review of genus Homo in the light of researchpublished since their study appeared. We find that, on balance, the availableevidence still supports their suggestion that Homo should be reconfigured suchthat it includes H. ergaster , H. erectus , H. heidelbergensis , H. neanderthalensis ,and H. sapiens but excludes H. habilis and H. rudolfensis . We also find that theproposed inclusion of the collection of Late Pleistocene specimens from the site ofLiang Bua, Flores, in the genus Homo as a new species, H. floresiensis, is notcompatible with Wood and Collard’s definition of the genus Homo.