In this excellent book, which is linked to the BBC TV series of the same name (available on DVD), Alice Roberts follows in the footsteps of our ancestors, who left Africa and ended up populating the whole world.
Roberts shows how the evidence from bones, artefacts and genes tells us that Homo sapiens (modern humans) evolved in Africa between 200,000 and 150,000 years ago and that all non-African humans throughout the world today are descended from one group of Homo sapiens who left Africa between 85,000 and 65,000 years ago.
On her journey Roberts meets people who personify and bring to life many of the debates relating to human evolution. For example, at Pinnacle Point in South Africa she meets one of the archaeologists who have been excavating Blombos Cave. It was here that shell beads and pieces of ochre with carved geometric patterns were found dating back 75,000 years. At the same place other pieces of ochre were found dating back to 164,000 years ago, showing that modern humans were painting by that date. This evidence shot down the theory held by some scientists that art (and therefore modern brains and behaviour) did not appear until about 40,000 years ago in Europe. (For more on this, see my review here on Amazon of Stephen Oppenheimer's book, "Out of Eden".)
Roberts meets some people who still refuse to accept the overwhelming evidence that all humans today are descended from African Homo sapiens. Some still cling to the untenable view that different so-called "races" of people evolved separately in different parts of the world from an earlier Homo species. For example, the Chinese government advocates the view that the people of China are special because they evolved separately from the rest of modern humanity, from Homo erectus in China. This has echoes of the time when Western racists claimed that white Europeans were superior and had come into existence separately from other "races".
But Roberts also meets the Chinese geneticist Jin Li, who "started off wanting to prove the patriotic theory that the modern Chinese had a heritage that stretched back, unbroken, to Homo erectus, a million years ago." To his surprise, Li's research actually proved that this was NOT the case. It showed that the "recent Out of Africa hypothesis" was correct. To his great credit, Li accepts the evidence, and Roberts praises his "open-mindedness and objectivity".
Roberts meets surviving hunter-gatherers and sees their egalitarian way of life. She then looks at the origins, only about 12,000 years ago, of settled societies and agriculture. She shows the contradictory nature of this change. The development of agriculture is usually seen as "progress", and it certainly created the conditions for a massive increase in population by producing a food surplus. This in turn provided the basis for the later growth of cities and "civilisation". But Roberts also shows that farming led to a worse quality and variety of diet and to a "general decline in health". (I would add that farming also paved the way for the development of class divisions, gender inequalities and war.)
Roberts shows that some questions still have to be resolved. For example: - Were modern humans responsible for the extinction of the Neanderthals? - Did modern humans interbreed at all with Neanderthals? - Exactly when and by what route did our ancestors first move into the Americas? - Did hunting by humans cause the extinction of large animals in various parts of the world? - Was it natural selection in relation to climate or sexual selection which led to the physical and facial differences between humans from different parts of the world? - Was it farmERS or farmING which spread across Europe from the Middle East?
Finally, Roberts shows throughout the book how the climate and climate change have had an effect on both the biology and culture of our ancestors. And she ends by warning that global solutions are needed now if we are to avert the dangers that climate change is facing us with today.