If we crack the “Aging Code,” we’re all in the shark tank.
About three years ago the radio tag from a nine-foot great white shark was found on a beach in Australia, and the story went viral that this great white had met a greater white. Newborn sharks famously eat one another, but the washed-up tag suggested the practice continues as they grow (and it does). It’s a shark-eat-shark world—for sharks.
Now, here’s what I didn’t know until I read Cracking the Aging Code: The New Science of Growing Old and What It Means for Staying Young, by theoretical biologist Josh Mittledorf PhD and science writer Dorian Sagan: Sharks don’t age.
Like some trees, great white sharks get bigger and stronger and more capable of reproduction as the years go by. While mini-greats struggle to get by, truly-greats can have more and more offspring, for breakfast, forever.
Now compare sharks to salmon born here in the Rogue River. The newly hatched salmon feast on bugs that feasted on the bodies of their parents. Once these young salmon reach a safe size, they leave the river and brave the Pacific, where they swim for years—showing no signs of aging—until it’s time to return home. Then powerful hormones kick in, the salmon stop eating, and they sprint upstream. Their bodies are already decomposing as they mate and die in the pool from which they came. The authors note, “Salmon destroy their own bodies in a blaze of steroids,” and in doing so they nourish not just their own eggs, but also the entire ecosystem. (That’s why the Pacific Northwest is a bioregion known as Salmon Nation.)
So, which would you rather be? A potentially immortal shark? Or a generative salmon? But before you answer, let’s learn more from this fascinating book about why we age.
One theory was that genes don’t replicate exactly; those genetic errors build up and cause us to break down. Yet that theory was debunked by the discovery of stem cells, which reproduce whatever kind of cell you need perfectly—and point instead toward immortality.
Another theory was that aging is caused by damage from “free radicals,” which gave birth to the antioxidant craze. In fact, free radicals fire up cell defenses—especially during exercise—and make people stronger and live longer. Too many antioxidants can shorten your life.
The more recent theory that aging is predicted by the length of the telomeres at the end of our chromosomes does seem to be accurate, but short telomeres are not the only reason we fall apart. Instead, the authors argue that aging is a complex code that is ancient even in terms of evolutionary time. In some creatures, lifespan can be dramatically increased with the manipulation of a few genes. In humans, however, the genes tied to aging are at the base of a “hierarchy of genes.” Cracking the aging code in humans is so difficult because our aging genes orchestrate declines in such a wide variety of systems.
And that raises its own questions: Why do our muscles turn to fat? Why do we absorb our own bones? What fuels the rising flames of inflammation? If evolution is survival of the fittest individual—the selfish gene—why is self-destruction embedded so deep? Why don’t we share the potential immortality of sharks?
The answer, the authors propose, it that evolution has evolved beyond the individual—and the selfish gene—to “group evolution” that protects entire populations from rapid expansion and collapse. As they explain:
“Nature has been forced to choose between faster reproduction and longer lifespan because fast reproduction and long life-span lead to population chaos. Once this choice is forced, then the benefits for evolveability become a decisive factor, leading to natural selection for shorter lifespans and higher fertility, rather than the other way around …”
I had to read that many times, but the point is this:
“Natural selection is not an all-out (neo-Darwinian) contest to see who can contribute more genes to the gene pool. For animals, that contest is absolutely forbidden by the requirements of fitting into an ecosystem… Aging with high fertility [us] wins out because it evolves faster than non-aging with low fertility [sharks]…”
Which leads the authors to this:
“Why is there a need for the young to grow up? What’s wrong with just keeping the adults we have, if youngsters aren’t fit enough to outcompete them? The answer is that constantly changing environments create the need for adaptability in the population. The population needs to turn over, to try new varieties, or it will eventually be overtaken by other populations that are growing stronger and more competitive over evolutionary time.”
Now, here’s the rub: The rate of change in the world is currently increasing so dramatically that generations should be turning over faster not just to be able to program our smartphones, but to keep our population down; otherwise, the “other populations” that overtake us may be cockroaches. But, of course, the goal of Cracking the Aging Code is Staying Young—to turn completely against group evolution and to satisfy the selfish gene.
How will that play out? One telling practice already in place, the book reports, is offshore blood banks where old tycoons fend off aging and support the young by buying their blood, which, if you stop to think about it, is mighty great-white of them.
To Age Well, Think Like a Salmon
As Cracking the Aging Code suggests, “Aging helps insure that the weakest of the community are not the youngest of the community but the oldest. The weakest are the ones the predators grab first.” In other words, our species evolved by literally sacrificing the old to protect the young.
The book also argues that humans have a set lifespan “so everyone doesn’t die at once.” Yet our “set” lifespan allows for variability to keep populations stable in varying conditions. Here’s how it works: When times are fat and happy (and populations grow fast), lifespan shrinks to make room for the next generation. That’s why eating a lot and taking it easy doesn’t make you stronger and healthier. Instead, it signals the body that conditions are safe to fall apart and die—a sacrifice for the good of the community.
When times are tough from famine or disease (and populations shrink), lifespan expands. That’s why strenuous exercise, near starvation, and a powerful purpose tend to increase longevity: All three are powerful signals to hang on, presumably to serve the young for the good of the community.
Stress signals the body to stay alive. The signal is actually a surrogate for the probability that my sisters and cousins are being killed (by famine or disease), and it would be a good time for me not to get old and die, for the continuity of our community.
So, how to age well? It’s not the ageless predation of a solo shark, fearful of others, always watching its back. Nor is it kicking back to enjoy the fruits of hard work. Instead, it is to tune in to our oldest and deepest calling to serve the good of the next generations: like salmon, traveling flat out, upstream, for the climax of a lifetime.