Sexual reproduction sets in motion the aging process, preventing our cells from achieving everlasting life.
Can the human body grow, develop, and improve without succumbing to aging? The answer is yes, as long as you are in your childhood years. During childhood, you experience growth in size, strength, and intelligence each year, all while maintaining a youthful appearance. Your muscles and bones develop, your immune system strengthens, and your cognitive abilities expand, all without the telltale signs of aging like wrinkled skin or deteriorating health. It’s only when you reach sexual maturity that things take a dramatic turn. The precise reasons behind this transformation are explained in a chapter from the book “Code of Longevity: What Makes Us Age, Why It’s Needed, and How to Cheat Evolution” by Belgian doctor and researcher Chris Verburg.
Consider the life of a Pacific salmon, which begins in the headwaters of rivers. As it grows, the fish swims downstream to the ocean and returns to its birthplace to lay eggs a few years later, after which it perishes. Why does this happen? To endure the arduous journey to the spawning grounds and the exhausting reproductive ritual, the salmon’s body is flooded with hormones, primarily cortisol, which, in such high quantities, exacts a toll on the body, perhaps even more than the journey itself. During spawning, the salmon inflicts damage on its body that is incompatible with sustaining life. In this case, the link between reproduction and death is starkly evident. For these fish, engaging in sex is synonymous with death.
While humans engage in sexual activity more frequently and less dramatically, an excess of sex hormones can still potentially shorten our lifespans. Laboratory animals given higher doses of testosterone tend to die sooner. Conversely, if you castrate a male brown house mouse, it can live almost six months longer—a notable extension for a creature with an average lifespan of just one year.
The answer to when aging actually begins and why may well lie in our sexual physiology. Although we commonly associate the onset of aging with turning 30, when we first notice gray hairs and decreased skin elasticity, the process actually starts much earlier. Some scientists propose that aging initiates as early as birth, but it’s more likely to commence around age 11. This hypothesis is grounded in two significant facts. First, it takes roughly 20 years to accumulate the conditions that eventually manifest as gray hair and under-eye wrinkles. Second, the statistical risk of death at age 11 is remarkably low—1 in 40,000. With a young and healthy body like that, one could theoretically live for 1,200 years or even longer. Unfortunately, the risk of death steadily climbs from there.
Every eight years, the likelihood of death doubles. A person at age 38 is twice as likely to die as someone at age 30, and an 88-year-old individual is twice as likely to die as an 80-year-old. This rule applies to women as well, although women tend to live longer than men on average, by about six years. Among individuals who reach 100 years of age, women outnumber men by a factor of at least four. Is this because the female body is simply better equipped to withstand the test of time from the start, possessing a higher “quality build”?
Here’s an interesting fact: There’s a phase in a man’s life when the risk of death triples compared to the norm. This period typically lasts from age 11 to 23 and is characterized by risky behaviors like reckless driving, fights, alcohol and drug abuse—essentially, activities that significantly increase the odds of death. Scientists aptly refer to this phase as “testosterone madness.” The choice of starting at age eleven is not coincidental; this is when a male’s body experiences a surge in sex hormones. In essence, we pay for our ability to reproduce with an increased risk of death. We’re somewhat reminiscent of Pacific salmon, except our reproductive period spans several decades rather than just a few days. Nevertheless, this still falls far short of our potential lifespan of 1,200 years. One could say we trade near-immortality for the act of reproduction. There is indeed a clear connection between reproduction and life expectancy—the more energy expended on reproduction, the faster we age.
Does this mean that if you engage in less sexual activity, you’ll live longer? Not necessarily. Regardless of sexual activity, your body continuously produces sex hormones. Furthermore, not all sex hormones are created equal. While an excess of male sex hormones may shorten lifespan, certain female sex hormones, such as estrogen, can provide protection against certain age-related diseases. This may explain why women tend to live longer; being female seems to be a favorable way to extend one’s life. But is there a chance for true immortality if we approach reproduction differently?
In nature, some organisms appear to possess a form of immortality. Consider the hydra, a tiny polyp that shows no signs of aging. Instead of sexual reproduction, it engages in “asexual reproduction.” The hydra simply releases one of its cells, which drifts away and grows into a new hydra. No elaborate mating rituals, no sexual competition—just release a cell, and you’re done.
Since any cell within a hydra can give rise to a new polyp, these cells never age. If they did, a ten-year-old hydra would release a ten-year-old cell, leading to the growth of a new polyp with aged cells. That’s why the stem cells of hydras remain eternally youthful. This phenomenon also applies to certain jellyfish, like the Turritopsis dohrnii, a small jellyfish found in oceans worldwide. Not only does it not age, but it can even “reverse” its age. When it feels old and frail, it somehow reverts its body to a youthful state, essentially rewinding its life cycle. It’s akin to a butterfly turning back into a caterpillar or a chicken regressing into an egg, only to emerge as a chick again. Some even refer to Turritopsis as the Benjamin Button of jellyfish.
Surprisingly, despite the apparent differences between humans and these polyps and jellyfish, we also possess cells within our bodies that never age a single day. These are our reproductive cells—egg cells in women and sperm cells in men. They, too, remain perpetually youthful. The reason is the same as for jellyfish: reproductive cells cannot age, as this would result in offspring being born with the cellular age of their parents. Fortunately, that’s not the case. Newborns are born fresh, young, and healthy.
In essence, our bodies harbor cells that defy aging, passed down from generation to generation, remaining forever young. While our bodies may grow old and eventually succumb to death, these immortal reproductive cells persist, ensuring the continuation of life. Every cell in your body is a product of the division of previous cells. You originated from your mother’s fertilized egg cell, which underwent countless divisions to form your body. Your mother, in turn, emerged from your grandmother’s egg cell, which traced its lineage back through generations. Thus, each cell in your body can be traced back to a common ancestral cell, dating back almost four billion years to the emergence of the first single-celled organisms on Earth. And every cell can only arise from a preexisting cell. These cells have divided and evolved, forming complex multicellular organisms—from jellyfish and reptiles to humans. And when you have offspring, your reproductive cells carry on this
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