What Do You Think You Are?
Good Fit
- Readers curious about science who shy away from technical books
- Anyone interested in family trees, DNA tests and the question «who were my ancestors?»
- Teenagers and young adults as a first look at many fields of science
Not a Fit
- Those who want to study one subject, such as genetics or consciousness, in depth
- Readers who tire of British cultural references such as TV shows
- Anyone looking for a fierce science-versus-religion polemic
Chapter one is the book's map. The author recalls asking readers of an earlier book to stand in front of a mirror and look at their body; here the idea is turned around and goes much deeper: what makes you different from other people, animals, even rocks? The scientific attitude is explained through Lee McIntyre's two conditions: empirical evidence and a readiness to change one's mind in the face of new evidence. Then comes the idea of «emergence»: none of the roughly 7×10²⁷ atoms in a body is alive, yet together they make life. The author says he will draw on fascinating experiments from the earlier book's website, while stressing that the two books stand on very different ground.
The chapter's boldest idea concerns the scale of our uniqueness. We share 99 to 99.9 per cent of our genes with other humans, about 96 per cent with a chimpanzee and 60 per cent with a banana. But Clegg warns that such comparisons are a reductionist trap: genes are only a small part of DNA, and «you» are also consciousness, personality and behaviour. Anyone with a relative living with dementia, the author notes, knows how hard such a change is.
Chapter two opens with a familiar scene from British television: working-class actor Danny Dyer discovers on a genealogy show that he descends from King Edward III and is thrilled. The author jokes that «you are royal too» and proves it with mathematics. Everyone has two parents and four grandparents, so ancestors double with every generation back. It is the famous story of the sage who asked for rice doubled on every square of a chessboard: 64 squares need 18.4 quintillion grains, about 600 years of the world's rice.
The role of family trees in history is explained in an interesting way too. For centuries a person's place in the world was measured not by biology but by lineage: it separated noble from commoner, landowner from peasant. The author illustrates England's three-class system with his own family. His father's parents were mill workers; his father started work without going to university, took evening classes and ended up running the company he worked for all his career. Class lines have blurred, yet the «upper class» still defines itself by the family it was born into rather than by achievement. That is where Dyer's delight comes from.
Apply the same arithmetic to 200,000 years of human history and the number of ancestors in one tree exceeds the number of atoms in the universe, although only about 110 billion people have ever lived. So family trees are not branching trees but tangled knots: the same ancestor appears again and again on different branches. In the middle of the chapter the author also explains evolution with two simple assumptions. He uses the millions of shades in a rainbow to show how arbitrary the idea of a «species» is, and stresses that «we did not descend from apes; we share a common ancestor».
The last part of the chapter is devoted to the concept of «race» and contains the book's clearest stance. According to the author, race has no biological basis. A 2002 study of 1,056 people from 52 populations found that 93 to 95 per cent of genetic variation lies within a single population. Skin colour is a simple pigment difference, like the author's own ginger hair as a young man. Clegg calls the «race» label «an excuse for xenophobia».
- Language that explains mathematical ideas (exponential growth, logarithms) with everyday examples
- Witty footnotes and personal family stories
- Respectful treatment of soul and religion with a clear scientific boundary
- Chapter endings that bridge into the next chapter
- A warm tone that addresses the reader directly as «you» throughout
The famous popular book on human identity through history and evolution
Covers genetics and genealogy in much more depth
The classic that tells science from atoms to humans with humour
Based on mitochondrial DNA, which passes only from mothers, the common maternal-line ancestor of everyone alive today, «Mitochondrial Eve», lived about 150,000 years ago. But the author points out that this follows only the female line. Yale statistician Joseph Chang shows that with two parents per person very few generations are needed to reach a common ancestor: for 7.7 billion people, about 33 generations, or 1,000 years.
In 2004 Chang, Douglas Rohde and Steve Olson published a more realistic model in Nature. According to it, the world's most recent common ancestor lived around 1415 BC, and the point at which someone was an ancestor of everyone alive today falls around 5353 BC. For Europe the figures are 600 and 1,000 years, so anyone of European descent can count Charlemagne as an ancestor. By the same logic we can claim kinship with the royal houses of China, Egypt and even Sumer. The author ends the chapter like this: among your ancestors are kings, but also murderers, thieves and beggars.
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