In this book Rutherford explains what the latest research in DNA tells us about humans – how we evolved, where we came from and how each of us is both unique and closely related to everyone else. He sets out his programme in the introduction:

The first half of this book is about the rewriting of the past using genetics, from a time when there were at least four human species on Earth right up to the kings of Europe into the eighteenth century. The second half is about who we are today, and what the study of DNA in the twenty-first century says about oour families, health, psychology, race and the fate of us. [p.9]

But don’t expect a simple linear account. Like genetics (= study of individual genes) and genomics (= study of entire genomes), the story is messy, tangled and confusing. In fact since Watson and Crick’s elucidation of the helix structure of DNA scientists have come to appreciate that our genes are far more complicated than they ever imagined in those early days. Just as the ‘Evolutionary Tree’ and your own family tree isn’t a simple branching structure, so this book branches out, loops back, criss-crosses and overlaps.

You’ll find out how it is that if you are European, you are related to everyone who was alive in Europe only 1,000 years ago (actually, the roughly 80% of those whose offspring survived to today). Go back 10,000 years and you – yes you, me, everyone – is descended from every human alive on Earth at that time. So when a celebrity on TV weeps to find she’s descended from Alexander the Great, or Charlemagne, or Socrates – well, so am I and (if you’re European) so are you.

You pick up other nice insights along the way.

• Icelanders are a rather closed group, and the country has almost complete records of every Icelander since the first settlements. There’s now an app for smartphones which will tell one Icelander how closely related they are to another. It’s popular for dating.
• Charles II of Spain, the last of the Hapsburgs and a sickly, deformed and crazy man, was more inbred than a child of two otherwise normal siblings.
• The ability of adults to digest lactose (milk) has spread in Europeans since the first farming of domesticated cattle about 5 – 6000 years ago – an example of continuing evolution.
• Your ear-wax says a lot about your genetic origins.

Towards the end of the book Rutherford gives a strong debunking of the concept of race, which he explains has no basis in genetics. Relatively small groups of humans migrated out of Africa to populate the rest of the planet, meaning that two black Africans are likely to be genetically more different from each other than a blonde blue-eyed Scandinavian is from a native of Borneo. Genes that we associate with ‘racial’ characteristics can be bred out of a family, or bred back in again, in a few generations.

Rutherford’s writing is authoritative, clear, witty, and informative. Follow him on the journey and you will reach the end impressed by what genetic research has achieved so far but appreciating how almost every new discovery raises even more complex questions.