Norman Owen-Smith - Only in Africa: The Ecology of Human Evolution

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Norman Owen-Smith 2021

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This book is dedicated to my extended family: my much-loved wife Margie, daughters Trishya and Lynne, and all of my former students.

Picking through a pile of elephant dung with a twig, quizzically chewing a leaf from a newly identified plant, interrupting a conversation to clap binoculars to his eyes and scrutinise something moving in the distance that is the characteristic behaviour of Norman Owen-Smith in his preferred habitat, African savanna. His keen curiosity about nature is combined with an incisively analytical mind and seemingly inexhaustible capacity for integrating his observations and ideas into the published literature. Driven by his enthusiasm for science, it was inevitable that Norman would achieve the international recognition that he has today as a leader in the field of animal ecology. Now, this book exemplifies his meticulous style of investigation, analysis and inference. It is a personal synthesis of Normans observations, notes and photographs collected during a rich career involving extensive travels across Africa. Generously integrated with information and ideas from the literature, the book not only reviews African savanna ecology and human evolution, but also articulates an important message for humanity. The message that it is only in Africa that humans could have evolved is as provocative as it is compelling from the line of reasoning laid out with characteristic rigour in this book.

It all stems from a sequence of unconnected events and circumstances, like an asteroid slamming into a planet. That happens all the time, somewhere in the universe, but when a particularly big one slammed into Earth about 66 million years ago the implications for the biosphere were profound. Non-flying dinosaurs and many other groups of organisms quickly died out, opening a game-changing evolutionary opportunity for our mongoose-sized mammalian ancestors. Over the next 60 million years, while the mammals radiated into a diversity of taxa over a widening range of body sizes and trophic niches, plate tectonics moved the continents around and broke them up. Different assemblages developed on different continents that had different shapes and positions on the Earths crust. By the time the common ancestor of humans and chimpanzees evolved, it occupied a species range in the middle of the big and geologically complex continent we call Africa, positioned squarely over the equator. That was crucial, because climatic cycles caused by the eccentric Earth-around-Sun orbit drove advances and retreats of the equatorial forest, taking 100,000 years per cycle. When the forest advanced, it covered mountains, plains and valleys; when it retreated, it left refugia of montane forest in a matrix of savanna. That forestsavanna ecotone, advancing and retreating at a rate suiting the speciation of large mammals, was the species pump that drove the dramatic radiation of wildlife (as we now view it) in African savannas. And among those radiating species there just happened to be a bipedal savanna-adapted large primate making its evolutionary appearance in just the right place and at just the right time. It coexisted with perennial supplies of big carcasses to scavenge from, diverse plant communities to gather from, and dry grass and wood to fuel lightning fires that could be weaponised and harnessed, sparking a complex social system.

Such is the sequence of events and circumstances that allowed the highly branched tree of human evolution to take root, and could only have , in African savannas, as Norman Owen-Smith explains here. Paradoxically, the biodiversity of African savannas particularly the megafauna that sustained our ancestral scavengers is now being shredded by the very species it spawned. This important book, by outlining the unique significance of African savannas for humanity, should leave readers with added resolve to conserve our ancestral habitat.