Part IV
Figure IV.1
Evolutionary transitions from ape to human.
(from Wikimedia commons)
Primates (order Primata) are basically herbivores, but are mostly not so large and mainly forest-dwelling. They are represented by a dazzling diversity of species throughout tropical forests where fruits are produced and trees retain foliage almost year-round. The platyrrhine (‘flat-nosed’) monkeys found in South America split off from the haplorhine (‘simple-nosed’) suborder inhabiting the ‘Old World’ tropics early in the Eocene ~50 Ma. Prosimians (bushbabies, lemurs and allies) diverged even earlier during the late Cretaceous 74 Ma, based on genetic evidence, and are most diverse in Madagascar. The monkeys inhabiting Africa and Asia (Cercopithecoidea) are separated from the apes (Hominoidea), which lack tails, at superfamily level. Among apes, the gibbons, found solely in Asia, are placed in a different family (Hylobatidae) from the remainder (Hominidae). Humans are allied with chimpanzees (Pan troglodytes and P. paniscus) and gorillas (Gorilla gorilla) in the latter family, but allocated to a distinct subfamily, the Homininae. Ecologically, we have diverged from other apes in habitat, locomotion and diet.
Among the African monkeys, baboons are largely ground-dwelling savanna inhabitants, penetrating only the margins of forest blocks. Some other monkeys also spend quite a lot of time on the ground, most notably the gelada (Theropithecus gelada), but remain mainly quadrupedal. Most monkeys augment their vegetarian diet with insects, baby birds or other animals when opportunities present. While chimpanzees kill monkeys and baby duikers, gorillas remain strictly vegetarian.
The first two chapters in this concluding section of the book establish the adaptive foundations laid by our primate ancestry, covering evolutionary linkages and ecological relationships. Thereafter, attention will be focused on the origins of our lineage and how our adaptations in locomotion, diet and culture relate to features of Africa’s savannas. In the concluding two chapters, I attempt to make sense of the taxonomic complexity of early hominins and look ahead to the place of Africa’s diverse ungulate fauna in changing human lifestyles.