The Weird, Ever-Evolving Story of DNA

The Weird, Ever-Evolving Story of DNA

Recent research, however, is giving Lamarck a measure of redemption. A subtle regulatory system has been shown to silence or mute the effects of genes without changing the DNA itself. Environmental stresses such as heat, salt, toxins, and infection can trigger so-called epigenetic responses, turning genes on and off to stimulate or restrict growth, initiate immune reactions, and much more. These alterations in gene activity, which are reversible, can be passed down to offspring. They are hitchhikers on the chromosomes, riding along for a while, but able to hop on and off. Harnessing epigenetics, some speculate, could enable us to create Lamarckian crops, which would adapt to a disease in one or two generations and then pass the acquired resistance down to their offspring. If the disease left the area, so would the resistance.

All of these heredities—chromosomal, mitochondrial, epigenetic—still don’t add up to your entire you. Not even close. Every one of us carries a unique flora of hundreds if not thousands of microbes, each with its own genome, without which we cannot feel healthy—cannot be “us.” These too can be passed down from parent to child—but may also move from child to adult, child to child, stranger to stranger. Always a willing volunteer, Zimmer allowed a researcher to sample the microbes living in his belly-button lint. Zimmer’s “navelome” included 53 species of bacteria. One microbe had been known, until then, only from the Mariana Trench. “You, my friend,” the scientist said, “are a wonderland.” Indeed, we all are.

Engineering the global genome could save millions of lives—or produce a chimeric hybrid of Gattaca and Jurassic Park. We could alter the gene pool of the future in ways we cannot yet even imagine, let alone understand. Zimmer is excited about the possibilities, but in a world where headlong innovation always trumps careful contemplation, he urges scientists and the public to learn from history. “We would do well,” he writes, “to look back at how the tools we’ve already invented have altered our ecological inheritance over the past ten thousand years.”

An old saw of biology runs “Evolution is cleverer than you are.” And ecology, involving as it does the dovetailed evolution of countless organisms in a constantly changing world, is cleverer than evolution. In Zimmer’s pages, we discover a world minutely threaded with myriad streams of heredity flowing in all directions, in variegated patterns and different registers—from a newt’s truncated, regenerating tail; to the pond in which the newt paddles; to the meadow where the pond fills and dries, fills and dries, down the centuries. The computing power alone required to play puppet master for such a scene, tugging and twirling the strings of its DNA, is staggering. Whether we have the wisdom to nurture nature is a question that Zimmer leaves, held aloft like a dandelion puff, for us to contemplate.