Mix and match

The Gene: An Intimate History. By Siddhartha Mukherjee. Scribner; 592 pages; $32. Bodley Head; £25.

THE first human with a genome that has been permanently modified in a lab could be born by the end of this decade. However innocuous the changes made, the baby’s birth will mark the first time that humanity has selectively interceded to change the genetic inheritance of future generations. That is an eventuality, Siddhartha Mukherjee argues in his new book, “The Gene”, for which the world is almost wholly unprepared.

The book begins in the tranquil gardens of St Thomas’s Abbey in Brno in the mid-19th century. It was here that Gregor Mendel, an Augustinian friar, began experiments with pea plants to see how biological traits are passed on from parents to offspring. As he bred peas with different characteristics—with purple or white flowers, or tall or dwarf plants—Mendel noticed that no purple-white flowers emerged, nor any plants of medium height. Instead, the original traits reappeared in different ratios after each cross. Mendel realised that these traits were being determined by independent particles of information, which every plant inherited from its parents. He had identified one of the fundamental characteristics of a gene, a discovery which would become a pillar of modern genetics.

“The Gene” ranges across 150 years, taking in every major advance in the field. It traces Charles Darwin’s thinking as he began to formulate his theory of evolution on his voyage to the Galápagos islands, and follows the thread all the way to contemporary China, where scientists are carrying out cutting-edge, but ethically troubling, genetic experiments with human embryos. Dr Mukherjee does not neglect the catastrophic missteps that science has taken, including the global rise of the eugenics movement, from the campaign by Francis Galton, Darwin’s half-cousin, to make it the “national religion” of Britain, to the atrocities committed by Nazi doctors in the second world war, which largely brought eugenics programmes to a halt.

Its grand scope means “The Gene” cannot explore the science to the same depth as other books such as Steven Rose’s classic, “The Chemistry of Life”. Nor is its narrative driven by a single powerful idea, as is Richard Dawkins’s “The Selfish Gene”, published 40 years ago.

Nonetheless, Dr Mukherjee uses personal experience to particularly good effect. In “The Emperor of All Maladies”, his earlier Pulitzer-winning history of cancer, it was his work as an oncologist that illuminated the science of the disease. In “The Gene” his family comes to the fore. He writes tenderly, for example, of his two mentally ill uncles: Rajesh, once “the most promising” of the brothers, and Jagu, who “resembled a Bengali Jim Morrison”. It is a poignant way to examine the genetics of schizophrenia: his own family’s history of mental illness leads him to studies of other families “achingly similar” to his own.

Returning to his uncles in the final chapter, Dr Mukherjee notes that mental illness can be accompanied by exceptional talents. He concludes his history with a 13-point manifesto for the post-genomic world. “Normalcy”, he writes, “is the antithesis of evolution.” This, then, is perhaps the most powerful lesson of Dr Mukherjee’s book: genetics is starting to reveal how much the human race has to gain from tinkering with its genome, but still has precious little to say about how much we might lose.