WHY ARE Africans black and Europeans white? And why do you have to dial the number "1" when telephoning the US from abroad?
Human groups have obvious differences that depend to some extent on their genes. But a deeper reason for our differences, suggests Luigi Cavalli- Sforza, an expert on human population genetics, comes from how we have adapted to our climate. Africans developed a black skin-colour to protect themselves from being scorched by the sun's ultraviolet radiation and developing skin cancer. Cereal-based diets left Europeans deficient in vitamin D and vulnerable to rickets. So they developed white skin to enable the sun's ultraviolet radiation to penetrate and provide the necessary vitamin.
Similarly, the face and body of the Mongols are the result of adaptation to Siberia's bitter cold. The body and head tend to be round, losing less heat. The nose is small, so less likely to freeze; the nostrils are narrow, so they warm inhaled air before it reaches the lungs; the eyes are protected from the cold air by fatty folds of skin.
All that means that belief in racial superiority is totally irrational. There are around 10 million social groups on earth that we can consider distinct from a genetic point of view. But none can be described as a "pure" race. Indeed, racial purity is impossible. Even partial "purity" would require at least 20 generations of inbreeding - brother-sister or parent-child mating - with devastating consequences for health and fertility.
Cavalli-Sforza maintains an active contempt for those who argue that their superior genes, chromosomes or DNA make them biologically superior. Such naivety emerged from the bad old science of yesterday. Only in the US, he suggests, are such beliefs still taken seriously - hence America's assertion of its alleged superiority by assigning itself the number 1!
Using the new science of palaeogenetics, which most of us first encountered in Jurassic Park, Cavalli-Sforza provides a panoramic history of humanity. The first human, Homo habilis, appeared around 2.5 million years ago, in Africa. He was followed by Homo erectus, two million years ago. …