Introduction

Among the more controversial hypotheses regarding hominoid evolutionary relationships is a Eurasian origin of the euhominoidea (Begun, 1997; Begun et al., 1997). This hypothesis, while supported by or at least consistent with other analyses based on independent lines of evidence (Gebo et al., 1997; McCrossin & Benefit, 1997; Stewart & Disotell, 1998), runs counter to most other recent proposals of hominoid evolutionary history (Andrews, 1992; Moyà-Solà & Köhler, 1995; Moyà-Solà et al., 1999; Harrison & Rook, 1997; Ishida & Pickford, 1997; McCrossin & Benefit, 1997; Andrews & Bernor, 1999). A key aspect of the Eurasian origin hypothesis is the phyletic position of early and middle Miocene hominoids relative to the euhominoidea (see Figure 10.1). Begun, et al. (1997) investigated hominoid relationships using a data base consisting of 240 characters in 13 taxa. The results of this research indicate that Kenyapithecus is the sister taxon to the clade that includes all living hominoids and all Eurasian Miocene hominids (Begun et al., 1997, p. 404, figure 1). Proconsul and Afropithecus are even further removed from this clade.

As suggested elsewhere (Begun, 1996; Begun et al., 1997; Stewart & Disotell, 1998; Heizmann & Begun, unpublished data) there are several palaeobiogeographic implications of this hypothesis. Euhominoids first appear, and may have originated in Eurasia following a single dispersal event from Africa towards the end of the early Miocene (Heizmann & Begun, unpublished data). All currently known fossil Eurasian hominoids are cladistically hominid, being more closely related to great apes and humans than to hylobatids (Figure 10.1 and Table 10.1).