Reframing aging as evolutionary success

In our modern society, aging tends to be something we ignore and then try to avoid. The dominant culture caters to young people, using them to gauge trends and styles and targeting their purchasing power. Meanwhile, the anti-aging industry is booming, with billions of dollars traded in creams, pills and treatments to stave off the look and feel of aging.

And yet, aging is undeniable. We are living longer than ever. And with more than half of the world’s countries having fertility rates below replacement level, the world’s population is aging. This “global aging” has alarming consequences for the working population and the health system.

“This potential to live seven decades is part of our species’ typical design,” said Michael Gurven, a professor of anthropology at UC Santa Barbara, whose new book takes an in-depth, long-term approach to aging. In “Seven Decades: How We Evolved to Live Longer”, he examines both the physiological and societal aspects of the latter part of human life, arguing that evolution actually designed humans to live at least seven decades.

According to Gurven, the gains in life expectancy we have seen over the past century have not extended our maximum longevity, but have helped ensure that many of us can live to older ages. Rather, the human ability to live well beyond menopause, a time shortly after most other species hit the proverbial Death Wall, evolved millennia ago, when we were all hunter-gatherers.

Although seven decades is longer than many would have thought possible in our distant past, we have seen improvements over the original mold. In most high-income countries, he added, the typical lifespan of an adult is now eight or nine decades.

By the way, what does aging mean?

In his writings, Gurven leads the way with an evolutionary perspective and a whirlwind journey around the world and through human history. While many books on aging focus on recent discoveries in the West or cover what we have learned over the past half century, he wanted to explore the phenomenon of aging beyond the number of years lived.

“I wanted to tell a story that goes further back in time, to the origins of our species and all the traits that make us who we are,” he said. “Aging is not a recent phenomenon, but what it looks like and how our ancestors experienced it remains a mystery.”

However, there are clues. Gurven drew on his work as an anthropologist studying contemporary non-industrial societies, whose hunting and foraging practices mark the vast majority of our evolutionary history. Throughout his career he has lived and studied several groups, including the Tsimané farmer-gatherers of the Bolivian Amazon, his research gathering information on the connections between their environment, lifestyle and physiology. Gurven stressed that these groups should not be considered living fossils. Instead, their lifestyles offer rare glimpses of what life can be like in a non-industrial environment.

Although life expectancy is short among hunter-gatherers, it is important to remember that its calculation is the average of all lifespans in a population. For most of human history, lives were cut short during childhood, he said. However, once an individual passes the challenge of early childhood, they can live to be 70 or 80 years old.

But life remains hard. Until recently, food insecurity, minimal health services, and a harsh lifestyle were part of the hunter-gatherer existence. That and senescence, the cellular process of deterioration with age, seem to conspire to make early demise a logical outcome.

“Most species age quickly and die when they are no longer able to reproduce,” Gurven explained. “This makes sense from the hard, gene-centric view of natural selection. Our ability to live decades beyond menopause is therefore a rare feature of our species.”

How did our ancestors manage to escape the pull of natural selection in their later years? It’s not just luck, Gurven points out. The key, he says in his book, is multigenerational cooperation. Sharing food and passing on knowledge and skills from elders to younger generations are essential for survival and reproduction, thereby increasing biological fitness in a way that has led to the evolution of a post-reproductive life stage.

“At some point in our evolutionary history, it became better to help the children and grandchildren we already have than to continue having new ones,” Gurven explained.

With the “ubiquitous sharing” of food and other resources typical of hunter-gatherers, even those who could not fully feed themselves (the young and the old) could still fulfill other tasks. While able-bodied adults spend much of their time securing food for themselves and the group, elders are politicians, ritual experts, conflict mediators, healers, and, of course, babysitters. They also make and repair tools, baskets, and targeted foods that require more intelligence than vigor to acquire. These various strategies geared toward helping the family and community, Gurven asserts, are at the root of our ancestors’ success and our long lives.

The meaning of “old”

What does it mean to be “old” for hunter-gatherers and farmers? Being “old” has less to do with age and more to do with the ability to stand on your own and with your community.

“It’s a fun question to ask people how old they might be if they never knew their age. But this is precisely the situation of many groups whose language does not include words for numbers beyond 10,” Gurven said. “For these people, you are ‘old’ when you can no longer work and have limited mobility.” Continuing participation in community life, through the transfer of knowledge and skills and lifelong learning, ensures the vitality of seniors and the development of younger people.

“Retirement doesn’t exist in subsistence-oriented populations,” Gurven said, pointing out that there may be lessons for those of us living in industrialized societies, where old age tends to signal a withdrawal from ordinary life, when in fact there is still much “untapped potential” in our elders that could be used to improve everyone’s quality of life.

“The implications of global aging for society are frightening,” Gurven added. “But we must recognize that one of the reasons for our species’ evolutionary success is the wide range of contributions that middle-aged and older adults have made to their families, their communities, and to society.

“For many of us, ‘old’ is a state of mind, an end. If we continue to learn and do new things and meet new people, we avoid feeling “old.” »