The Gene: An Intimate History

by Siddhartha Mukherjee

Memories sharpen the past; it is reality that decays.

It is tempting to write the history of technology through products: the wheel; the microscope; the airplane; the Internet. But it is more illuminating to write the history of technology through transitions: linear motion to circular motion; visual space to subvisual space; motion on land to motion in air; physical connectivity to virtual connectivity.

If human physiology is visualized as a vast global telephone network with interacting nodes and networks, then our current medicinal chemistry touches only a fraction of a fraction of its complexity; medicinal chemistry is a pole operator in Wichita tinkering with a few lines in the network’s corner.

What have I in common with Jews? I have hardly anything in common with myself. —Franz Kafka

The question is not, can you, given an individual’s skin color, hair texture, or language, infer something about their ancestry or origin. That is a question of biological systematics—of lineage, of taxonomy, of racial geography, of biological discrimination. Of course you can—and genomics has vastly refined that inference. You can scan any individual genome and infer rather deep insights about a person’s ancestry, or place of origin. But the vastly more controversial question is the converse: Given a racial identity—African or Asian, say—can you infer anything about an individual’s characteristics: not just skin or hair color, but more complex features, such as intelligence, habits, personality, and aptitude? Genes can certainly tell us about race, but can race tell us anything about genes?

Sex, one of the most complex of human traits, is unlikely to be encoded by multiple genes. Rather, a single gene, buried rather precariously in the Y chromosome, must be the master regulator of maleness.I Male readers of that last paragraph should take notice: we barely made it.

The most intriguing correlations obtained by the Minnesota study were also among the most unexpected. Social and political attitudes between twins reared apart were just as concordant as those between twins reared together: liberals clustered with liberals, and orthodoxy was twinned with orthodoxy. Religiosity and faith were also strikingly concordant: twins were either both faithful or both nonreligious. Traditionalism, or “willingness to yield to authority,” was significantly correlated. So were characteristics such as “assertiveness, drive for leadership, and a taste for attention.”

It is a testament to the unsettling beauty of the genome that it can make the real world “stick.” Our genes do not keep spitting out stereotypical responses to idiosyncratic environments: if they did, we too would devolve into windup automatons. Hindu philosophers have long described the experience of “being” as a web—jaal. Genes form the threads of the web; the detritus that sticks is what transforms every individual web into a being. There is an exquisite precision in that mad scheme. Genes must carry out programmed responses to environments—otherwise, there would be no conserved form. But they must also leave exactly enough room for the vagaries of chance to stick. We call this intersection “fate.” We call our responses to it “choice.” An upright organism with opposable thumbs is thus built from a script, but built to go off script. We call one such unique variant of one such organism a “self.”

It took the full force of human genetics to bring sanity to the study of madness.

“We of the craft are all crazy,” Lord Byron, the high priest of crazies, wrote. “Some are affected by gaiety, others by melancholy, but all are more or less touched.”

Every genetic “illness” is a mismatch between an organism’s genome and its environment. In some cases, the appropriate medical intervention to mitigate a disease might be to alter the environment to make it “fit” an organismal form (building alternative architectural realms for those with dwarfism; imagining alternative educational landscapes for children with autism). In other cases, conversely, it might mean changing genes to fit environments. In yet other cases, the match may be impossible to achieve: the severest forms of genetic illnesses, such as those caused by nonfunction of essential genes, are incompatible with all environments. It is a peculiar modern fallacy to imagine that the definitive solution to illness is to change nature—i.e., genes—when the environment is often more malleable.

Show me that you can divide the notes of a song; But first, show me that you can discern Between what can be divided And what cannot. —An anonymous musical composition inspired by a classical Sanskrit poem