Similarly, grief might be diminished but so might tenderness. The question is: who will choose what procedures are acceptable and who receives them? And what might be the unintended consequences? Illness might progressively vanish, but so might identity, if we tinker too much, says Mukherjee. Mukherjee is excellent on the ethical problems that will be presented by our growing ability to unpick the DNA of our fellow citizens. In other words, we will be able to manipulate our own genetic future, snipping genes from embryos or adding new ones.”

“Soon we will be ready to write our own instructions. “We have reached the stage where, as intelligent organisms, we are learning how to read the instructions for our own creation,” says Mukherjee. Soon, we will start to tackle more complex disorders – cancers or heart diseases – by altering or replacing entire groups of genes. Already scientists are finding ways to alter the genetic makeup of children with harmful mutations including cystic fibrosis and muscular dystrophy. And that refers not just to interventions we might make in a person’s upbringing but to those whose DNA we may be able to change.

The trouble, says Mukherjee, is that we are going to encounter this sort of thing increasingly often as our ability to unravel the DNA of our fellow citizens becomes more powerful.

Put that way, the notion looks unpleasant. To his credit, Mukherjee is suspicious of the ethics of a scheme whereby an authority, having genotyped children in a particular area, could then be allowed to choose who is worthy of the attention of the best teachers and the most resources and who is not. The idea of a resilience gene has since taken root, leading psychologists to propose that susceptible short-variant children – the worst behaved but better at responding to counselling – be targeted for scarce and costly intervention. “It is as if resilience itself has a genetic core,” says Mukherjee in this broad-ranging guide to modern genetics and its impact on life. That grim start to life was not quite so hopeless as it seemed. They found the former group, while more prone to antisocial behaviour, was also more likely to react positively to counselling. But the researchers went further, providing counselling for short-variant binge drinkers and long-variant “normals” to see how each group responded to help from others. Combine a deprived background with a set of “bad” genes and your chance in life was doomed, it appeared. Sure enough, the scientists found that possessors of short variants were more likely to binge drink, use drugs and be sexually permissive.

The gene book siddhartha mukherjee