Reading and Writing Life

In 2012, in the pages of a scientific journal, two researchers described a way to edit the code of life almost as easily as a word processor edits a sentence: a molecular tool, borrowed from the ancient war between bacteria and the viruses that prey on them, that could be aimed at any chosen spot in any genome and told to cut. They called it CRISPR, and within a single decade it had traveled from that paper into hospitals, where it has now cured people of diseases, sickle-cell anemia among them, that had tormented families for all of recorded history. The four-letter code that Part II spent its wonder on, the script that every living thing is written in, we can now not only read but rewrite.

And read it we can, at a speed that beggars belief. The first human genome took a global effort more than a decade and billions of dollars to spell out, around the year 2000. Today those same three billion letters can be read in about a day for a few hundred dollars, and the price is still falling. We have recovered the genomes of Neanderthals and Denisovans from specks of ancient bone, as an earlier chapter described; we read the genome of a tumor to choose the drug that will fight it; we have begun to map the microbiome, the teeming community of trillions of microbes living in and on each of us, whose genes outnumber our own many times over and whose fortunes, we are learning, are tangled with ours in ways the old picture of the sealed-off individual never dreamed. And beyond reading and editing lies writing: in the laboratory, researchers have now assembled a working genome from raw chemicals and booted up a living cell that runs on it, the first stammering steps toward composing life from scratch rather than only revising what already lives.

This is a genuinely new kind of power, and it wears two faces at once, which by now is a familiar shape in this book. One face is the oldest human dream made real, the healing of what could not be healed: cures for inherited disease, crops that feed more people from less land, perhaps one day a real purchase on aging itself, the body repaired according to its own instructions. The other face an earlier chapter named among the perils of the age. The same falling cost and rising ease that put cures within reach of a modest laboratory also, year by year, lower the floor beneath catastrophe, drawing the deliberate design of a pathogen down out of the sole grip of great powers and toward the reach of the few, the careless, and the cruel. And beneath even that lies a quieter unease that has nothing to do with malice: that we have gained the power to edit the human inheritance itself, to make changes that would run down every generation after us, well before we have anything like the wisdom to know which changes we should make, or the humility to be sure we understand a system that four billion years of evolution assembled and that we have been able to read for only a few decades. We have learned to write in the oldest language there is. We have not yet learned what we ought to say in it. That gap, between the power and the wisdom to wield it, is the through-line of this entire stretch of the book, and it yawns nowhere wider than here, with our hands on the code of life itself.