Out of Africa’s Eden: The Peopling of the World
by Stephen Oppenheimer
(Jonathan Ball)
Over the past century or so scientists have had many conflicting theories about human origins (and what we did next). Several studies on human genetics over the past two decades have, however, led us to one undeniable conclusion: the entire human race descends from individuals who lived in Africa.
This complex story, an intricate journey through time and space, is explored in great breadth and depth by Stephen Oppenheimer. You will need a basic grasp of several disciplines to follow his arguments, but it’s worth the effort.
Oppenheimer starts his book by putting us in a hypothetical queue: next time you’re standing in a queue in a bank, post office or supermarket, take a look at the incredible diversity of people around you. The ancestors of modern South Africans come from many continents: chiefly Africa, Europe, India, Asia. You probably believe you are unrelated to most of these people. You all look so different, you are from different races, cultures, languages, continents, far apart, separate. But you’re cousins under the skin.
Every human alive today is descended from one woman, who lived in Africa about 150 000 years ago. And every man alive today is descended from one man, who also lived in Africa aeons ago. How do we know? From scraps of evidence we each inherit from our parents and pass on to our children. This evidence is encoded in our DNA. We all inherit mitochondrial DNA from our mothers, but only daughters pass it on. Likewise, only boys get a Y-chromosome from their fathers.
Predictably, scientists have dubbed our ur-parents “Adam” and “Eve”, although they did not know each other, and were not alive at the same time, but we, their great-grandchildren, reflect the entire spectrum of human types.
These two genetic strands were both present in a group of about 100 people who migrated out of Africa about 80 000 years ago across a narrow strait at the southern end of the Red Sea — a place with the eerie Arabic name Bab al Mandab, the Gate of Grief.
Oppenheimer is a tropical paediatrician who has for more than two decades worked in genetic research in Asia. In the early 1980s, while working in New Guinea, he discovered that a mild inherited blood disease, a-thalassaemia, gave people immunity to malaria. In subsequent research throughout the Pacific region he realised that this genetic disorder was evident wherever people of the Polynesian type had settled. He realised that similar genetic markers present in the world’s diverse populations could be used to trace the human voyage around the globe.
Oppenheimer describes this ages-long journey in mind-boggling detail. Along the way, he examines other aspects of human existence: when we learned to walk upright, the growth of our big brains, the development of speech, the first stirrings of culture, and much more.
But it is the vast scale of our epic journey that makes Out of Africa’s Eden compelling reading. Our ancestors walked out of Africa towards the east, literally eating their way along the coastline, getting all the way to Australasia in a surprisingly short time, a mere 10 000 years. Along the way groups split off, settled, were fruitful and multiplied, especially on the Indian subcontinent and the fertile crescent of the Middle East. From there they migrated in all directions: north and east into Asia and the Americas, west into Europe, even back into Africa. In the course of these long, slow migrations, the various human types, usually called races, evolved.
Some of the discussion is highly technical, but Oppenheimer’s synthesis of the evidence from palaeontology, archaeology, climate studies, linguistics, genetics, geology and other disciplines makes wading through the heavy stuff worthwhile. The many maps and tables help to illuminate the text; pity there’s no separate, comprehensive bibliography and that the index is inadequate.
Still, next time you hear the song We Are Family, believe it.