African beginnings

We saw in the previous chapter how climate-induced habitat and landscape changes acted as catalysts to human range expansions, shifts and contractions. This chapter explores these processes in greater detail.

Novelty in the genus Homo was generated repeatedly in eastern Africa. It is not unexpected that the sources of biological novelty should be tropical given the tropical nature of the primates as a whole (Foley, 1987) and the scarcity of species that reach away from the tropics. The nature of the distribution of the ape lineage and the distribution of open savannah-type habitats close to tropical forest make an African tropical origin a virtual certainty and this is well supported by the fossil evidence (Stringer & Gamble, 1993; Akazawa, 1996a; Klein, 1999). Novelties arose repeatedly in the Homo lineage but they also occurred deeper in time with the adaptations to open environments and departures from frugivory and herbivory of the pre-Homo forms.

Arid communities became established in East Africa by 23 Myr and there has been no real change in vegetation in the past 15.5 Myr. C4 vegetation, characterised by grasses and sedges in warm arid, open, habitats, appeared around 15.3 Myr bp (Kingston et al., 1994). Early hominid evolution took place in sub-Saharan Africa in situations of increasing environmental instability that led to forest contraction and at the expense of open environments (Foley, 1987; Foley & Lee, 1989; Bobe et al., 2002).