David Sinclair

Lifespan


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Whether or not she actually made it to that age really doesn’t matter; others have come within a few years of that age but most of us, 99.98 percent to be precise, are dead before 100.

      So it certainly makes sense when people say that we might continue to chip away at the average, but we’re not likely to move the limit. They say it’s easy to extend the maximum lifespan of mice or of dogs, but we humans are different. We simply live too long already.

      They are wrong.

      There’s also a difference between extending life and prolonging vitality. We’re capable of both, but simply keeping people alive—decades after their lives have become defined by pain, disease, frailty, and immobility—is no virtue.

      Prolonged vitality—meaning not just more years of life but more active, healthy, and happy ones—is coming. It is coming sooner than most people expect. By the time the children who are born today have reached middle age, Jeanne Calment may not even be on the list of the top 100 oldest people of all time. And by the turn of the next century, a person who is 122 on the day of his or her death may be said to have lived a full, though not particularly long, life. One hundred and twenty years might be not an outlier but an expectation, so much so that we won’t even call it longevity; we will simply call it “life,” and we will look back with sadness on the time in our history in which it was not so.

      What’s the upward limit? I don’t think there is one. Many of my colleagues agree.14 There is no biological law that says we must age.15 Those who say there is don’t know what they’re talking about. We’re probably still a long way off from a world in which death is a rarity, but we’re not far from pushing it ever farther into the future.

      All of this, in fact, is inevitable. Prolonged healthy lifespans are in sight. Yes, the entire history of humanity suggests otherwise. But the science of lifespan extension in this particular century says that the previous dead ends are poor guides.

      It takes radical thinking to even begin to approach what this will mean for our species. Nothing in our billions of years of evolution has prepared us for this, which is why it’s so easy, and even alluring, to believe that it simply cannot be done.

      But that’s what people thought about human flight, too—up until the moment someone did it.

      Today the Wright brothers are back in their workshop, having successfully flown their gliders down the sand dunes of Kitty Hawk. The world is about to change.

      And just as was the case in the days leading up to December 17, 1903, the majority of humanity is oblivious. There was simply no context with which to construct the idea of controlled, powered flight back then, so the idea was fanciful, magical, the stuff of speculative fiction.16

      Then: liftoff. And nothing was ever the same again.

      We are at another point of historical inflection. What hitherto seemed magical will become real. It is a time in which humanity will redefine what is possible; a time of ending the inevitable.

      Indeed, it is a time in which we will redefine what it means to be human, for this is not just the start of a revolution, it is the start of an evolution.

PART I

      WHAT WE KNOW

      (THE PAST)

      ONE

      VIVA PRIMORDIUM

      IMAGINE A PLANET ABOUT THE SIZE OF OUR OWN, ABOUT AS FAR FROM ITS STAR, rotating around its axis a bit faster, such that a day lasts about twenty hours. It is covered with a shallow ocean of salty water and has no continents to speak of—just some sporadic chains of basaltic black islands peeking up above the waterline. Its atmosphere does not have the same mix of gases as ours. It is a humid, toxic blanket of nitrogen, methane, and carbon dioxide.

      There is no oxygen. There is no life.

      Because this planet, our planet as it was 4 billion years ago, is a ruthlessly unforgiving place. Hot and volcanic. Electric. Tumultuous.

      But that is about to change. Water is pooling next to warm thermal vents that litter one of the larger islands. Organic molecules cover all surfaces, having ridden in on the backs of meteorites and comets. Sitting on dry, volcanic rock, these molecules will remain just molecules, but when dissolved in pools of warm water, through cycles of wetting and drying at the pools’ edges, a special chemistry takes place.17 As the nucleic acids concentrate, they grow into polymers, the way salt crystals form when a seaside puddle evaporates. These are the world’s first RNA molecules, the predecessors to DNA. When the pond refills, the primitive genetic material becomes encapsulated by fatty acids to form microscopic soap bubbles—the first cell membranes.18

      It doesn’t take long, a week perhaps, before the shallow ponds are covered with a yellow froth of trillions of tiny precursor cells filled with short strands of nucleic acids, which today we call genes.

      Most of the protocells are recycled, but some survive and begin to evolve primitive metabolic pathways, until finally the RNA begins to copy itself. That point marks the origin of life. Now that life has formed—as fatty-acid soap bubbles filled with genetic material—they begin to compete for dominance. There simply aren’t enough resources to go around. May the best scum win.

      Day in and day out, the microscopic, fragile life-forms begin to evolve into more advanced forms, spreading into rivers and lakes.

      Along comes a new threat: a prolonged dry season. The level of the scum-covered lakes has dropped by a few feet during the dry season, but the lakes have always filled up again as the rains returned. But this year, thanks to unusually intense volcanic activity on the other side of the planet, the annual rains don’t fall as they usually do and the clouds pass on by. The lakes dry up completely.

      What remains is a thick, yellow crust covering the lake beds. It is an ecosystem defined not by the annual waxing and waning of the waters but by a brutal struggle for survival. And more than that: it is a fight for the future—because the organisms that survive will be the progenitors of every living thing to come: archaea, bacteria, fungi, plants, and animals.

      Within this dying mass of cells, each scrapping for and scraping by on the merest minimums of nutrients and moisture, each one doing whatever it can to answer the primal call to reproduce, there is a unique species. Let’s call it Magna superstes. That’s Latin for “great survivor.”

      It does not look very different from the other organisms of the day, but M. superstes has a distinct advantage: it has evolved a genetic survival mechanism.

      There will be far more complicated evolutionary steps in the eons to come, changes so extreme that entire branches of life will emerge. These changes—the products of mutations, insertions, gene rearrangements, and the horizontal transfer of genes from one species to another—will create organisms with bilateral symmetry, stereoscopic vision, and even consciousness.

      By comparison, this early evolutionary step looks, at first, to be rather simple. It is a circuit. A gene circuit.

      The circuit begins with gene A, a caretaker that stops cells from reproducing when times are tough. This is key, because on early planet Earth, most times are tough. The circuit also has a gene B, which encodes for a “silencing” protein. This silencing protein shuts gene A off when times are good, so the cell can make copies of itself when, and only when, it and its offspring will likely survive.

      The genes themselves aren’t novel. All life in the lake has these two genes. But what makes M. superstes unique is that the gene B silencer has mutated to give it a second function: it helps repair DNA. When the cell’s DNA breaks, the silencing protein encoded by gene B moves from gene A to help with DNA repair, which turns on gene A. This temporarily stops all sex and reproduction until the DNA repair is complete.

      This makes sense, because while DNA is broken, sex and reproduction are the last things an organism should be doing. In future multicellular organisms, for