Want to live to 150? The world needs more humans.

In 2020, Massachusetts joined the list of 25 American states recording more deaths than births. In the same year, only two countries in the Organization for Economic Co-Operation and Development had a fertility rate of at least 2.1 children born per woman — which is needed to maintain population replacement.

Malthus was right in one sense: The size of a population is a huge factor in its economy. But he failed to anticipate that we might come to lack healthy adults to come up with and fund solutions for humanity’s most pressing crises. He did not foresee — and many people still do not appreciate — that one 21st-century farmer, engineer, or baker can produce far more resources than she consumes in her lifetime. Just like Paul Ehrlich, who wrote in the bestselling 1968 book “The Population Bomb” that “the mother of the year should be a sterilized woman with two adopted children,” Malthus was gravely off base.

Last year, the global population crossed 8 billion. In recent decades, it has also enjoyed the highest levels of nourishment, housing conditions, comfort in travel, and education in all of history, as Steven Pinker documents in “Enlightenment Now.” The 20th century’s scientific breakthroughs gave us vaccines, chemotherapies, and antibiotics. In just one century, average life expectancy rose from 31 to 68.

But this extraordinary leap in life expectancy happened without a corresponding increase in health-span. Because aging itself hasn’t been considered a medical disorder, people today generally spend half their lifetime in declining health.

Some 90 percent of all deaths in developed countries are due to to age-related decline, including cancers, heart disease, dementias, and severe infection. By 2029, the United States will spend an unprecedented half of its annual federal budget — $3 trillion, or thrice its military outlay — on adults 65 or older, on measures like Alzheimer’s care and retirement pensions. By 2050, Japan will lose some 20 million people, while Brazil’s senior population is set to triple. About 50 million Americans — predominantly women — are now unpaid caretakers of older adults, at a $500-billion-a-year opportunity cost.

Could new technologies solve these problems by extending the healthy years of long-lived populations? This is the question the emerging field of aging research has set out to answer — and labs in some of Boston’s elite institutions are among those with data suggesting that aging can be not just slowed down, but also reversed.

If we solve aging, we may well solve our emerging underpopulation crisis.

And we have, I will suggest, an ethical imperative to do both — even though tackling aging itself as a medical problem remains a contrarian idea.

Two centuries after Malthus remarked that “we should court the return of the plague” and “reprobate remedies for ravaging diseases,” a growing number of scientists, investors, and bioethicists believe we can and should engineer longer and healthier lives.

In his 2019 book “Lifespan,” Harvard geneticist David Sinclair wrote that “aging may be more easily treatable than cancer.” After several years working to understand and control the biological mechanisms of aging, he tells me, his lab is showing that aging may be “like scratches on a CD that can be polished off.” His team’s latest findings were published in the journal Cell on Jan. 12. Their paper suggested mammalian aging is in part the result of a reversible loss of epigenetic information: our cells’ ability to turn genes on or off at the right time.

In “Lifespan,” Sinclair points out that if we cloned a 65-year-old person, the clone wouldn’t be born old — which says a lot about how our “youthful digital information” remains intact, even if this 65-year-old’s genetic expression and cell regulation mechanisms are presently functioning less than optimally. There seems to be, as Sinclair notes, a backup information copy within each of us, which remains retrievable.

There is no guarantee that cellular reprogramming will work in humans — but after decades of (at times, highly criticized) work, Sinclair’s lab published what is set to become a widely influential study on the role of epigenetic change in aging. Futurist Peter Diamandis, trained as a physician and now executive chairman of the XPrize Foundation (a science and technology nonprofit for which I consult), tells me aging must be “either a software or a hardware problem — solvable by a species capable of developing vaccines for a novel virus within months.”

Indeed, the human life expectancy of 80 years and the current health span of roughly 40 (when most chronic illnesses begin to appear) are not just economically alarming — they don’t appear to be a biological imperative.

Humans are one of only five species in the animal kingdom that undergo menopause. Lobsters are often more fertile at 100 than at 30. Naked mole rats’ chances of dying do not increase with age. Bowhead whales live to 200 and are incredibly resistant to the diseases of aging.

Other examples abound — and the genetic therapies that could translate these features into human bodies are becoming increasingly precise. Promising research in human genes, cells, and blood drives home that aging is a malleable process that can be decoupled from the passing of time.

It is well established that aging can be sped up, slowed down, and reversed. This is done every day with diet, mental health practices, and exercise. What’s novel about this century’s science is the promise to engineer therapies that might control the aging process more effectively.

By conservative estimates, robust aging therapies could free up half the American federal budget every year, making it possible for more older adults to remain in the workforce. These therapies could effectively prevent nearly all cancers, dementias, and heart diseases, and even avert fiascos of communicable diseases like the COVID pandemic, in which age is the major risk factor for severe disease. (COVID-19 will cost the global economy $12.5 trillion by 2024.) Low-income and other vulnerable populations stand to gain the most, because they suffer the most when diagnosed with age-related diseases.

Yet despite the enormous promise of aging therapies, the field hasn’t attracted a correspondingly large amount of government funding. Out of the $4 billion devoted to the National Institute of Aging yearly, only $300 million goes to fundamental aging research.

Why?

It cannot be because aging research lacks scientific results. Research into Alzheimer’s disease may have fewer credible results than the far younger field of aging — yet it enjoys many times more funding. If an idea is sufficiently compelling to a civilization (like the reversal of climate change is becoming to ours), then replicable scientific results can be the goal of the research, not the prerequisite for undertaking it.

For too long, aging research was incompatible with Western culture. It was only in 1906 that Alzheimer’s was recognized as a disease, and only around the 1920s that the public narrative of cancers shifted from their being godsends (with which to interfere would be hubristic) to intervenable disorders. Aging was thought to be a feature designed by evolution to furnish human lives with meaning.

Yet natural selection only rarely optimizes for human happiness. Evolution favors the flourishing of genes, not organisms. And as several evolutionary biologists have remarked, our genes live on when we reproduce — making our bodies evolutionarily superfluous.

It follows that aging therapies would be no less natural than cancer therapies or vaccines designed to tackle any other pandemic in which older adults are the most vulnerable. And, as Harvard geneticist George Church tells me, “there is no reason why aging therapies should cost more than the recent COVID vaccines — as little as $2 per dose.”

Aging research is woefully underfunded, understudied, and understaffed. For every aging lab, there are thousands of cancer labs globally — even though 96 percent of cancers happen to adults aged 35 or older.

Democratic governments declare wars on the diseases of aging (though not on aging itself) because a full 100 percent of the population is onboard. By comparison, only 38 percent of Americans believe aging should be slowed down or reversed, according to the Pew Research Center. As a result, a mere 0.5 percent of the National Institutes of Health budget is devoted to fundamental aging research.

In its best years, research on the biology of aging receives $3 billion in private funding — or less than half the market size of bug spray.

The problem with leaving our aging crisis for venture capitalists to try to solve is twofold. First, the priorities of the private sector are not to protect vulnerable populations or decrease human suffering. Venture capital often doesn’t care about the grief of watching one’s parents die; the agony of becoming an unpaid caretaker to a loved one; or of losing one’s cognitive abilities, bit by bit — unless alleviating any of this suffering can be monetized within 10 years of investment. Second, without governmental funding on the scale of what was mustered for COVID vaccines, the private sector is unlikely to deliver safe and effective aging therapies very soon.

Despite non-trivial advancements in the science, the private funding flowing into longevity isn’t enough to attract the world-class talent warranted by a goal like age reversal. In the past, small and underfunded teams have produced astonishing breakthroughs in science — and with advancements in AI, this will increasingly be the case. But for a goal like age reversal — just as for the reversal of climate change — a shift in public narrative may be imperative.

Waiting until global warming has been reversed to then convince the voting public of the merits and urgency of climate science would be an ill-timed strategy — just as waiting for better results in aging science to then decide this socioeconomic crisis should be solved may be unsound.

The average voting person’s disapproval of aging research in the West may soon cause non-democratic governments to lead the charge in this made-in-America idea. Saudi Arabia has the one government openly devoted to age reversal, with a $1 billion annual fund. Alex Zhavoronkov, CEO of Insilico Medicine, a longevity-oriented drug-discovery company that has raised over $415 million, tells me he moved the company’s R&D to China to capitalize on “half a trillion dollars’ worth of infrastructure and hundreds of thousands of scientists [provided by the government] to enable AI-designed drugs.”

Ultimately, Americans struggle to accept aging research because we fear its moral implications. If we engineer ourselves out of aging and live unprecedentedly long, healthy, and abundant lives, would we risk engineering ourselves, too, out of meaning?

With longer lives, we would have to guard against a kind of reverse ageism. Older adults may retain undue power, stifling opportunities for younger people. This does not obviate our ethical imperative to achieve a more humane health system.

If we lived longer, would there be more traffic or higher carbon dioxide levels? In the short term, yes. In the long term, however, more minds translate into better solutions. A planet with 10 billion people is likely to have greater housing and nourishment needs. But it is also far likelier to have electric self-driving cars, high-density and digitally optimized mass timber buildings, interplanetary settlements (for which we will need aging drugs), and hyper-productive vertical farming.

In the end, no technology is ever fully good. Surveys show that the American public believes that for aging therapies to be morally sound, they must be “safe, effective, affordable, available to all, and cause no side effects.” But that’s self-deceiving. Costly and only occasionally safe or effective cancer therapies are a case in point. As a rule, solutions create unintended problems, for which new solutions must be devised. The answer isn’t to stop funding scientific progress, but to refine it until clinical therapies achieve a favorable risk-benefit profile.

When I ask George Church about these ideas, he looks at me with the resoluteness of a seasoned scientist — but in his eyes I see a childlike, nonconformist spark. “Age reversal can be done,” he tells me. “And it will be more humane than anything that happens in nature, if we do it right.”

Raiany Romanni, a philosopher and bioethicist in Boston, is working on a book about the ethics of age-reversing technologies.