Not Time To Die

MOVEMENT AND LOVE TELL OUR BODIES IT IS NOT YET TIME TO DIE: THE ACTIVE GRANDPARENT HYPOTHESIS   

                                                                         John Ingham

In a previous post, I took issue with the opinion that high levels of endurance exercise are inherently harmful. Here, I amplify my critique by noting the various ways aerobic exercise supports health and promotes longevity. There are so many, in fact, that we are led to suppose that our ability to benefit from endurance exercise has been a defining feature of human nature from the very beginning. Some benefits of exercise are metabolic adaptations to stress. Others are effects of exercise activating longevity genes and proteins. And some result from how endurance exercise can encourage connection with people and the out of doors. In all three, it appears that aerobic exercise is signaling organs and tissues throughout the body that it is not yet time to die.

METABOLIC HEALTH

Metabolic disorder underlies chronic diseases, including heart disease, many cancers, and type 2 diabetes. Its markers include high blood pressure, high serum triglycerides, low serum HDL, elevated blood glucose, obesity, and insulin resistance. Lack of exercise and high glycemic diets are principal causes of metabolic disorder. Some effects of exercise on metabolism are mediated through the mitochondria, tiny organelles within cells that turn fat and sugar into chemical energy and regulate reactive oxygen species (ROS) production. Mitochondrial dysfunction is associated with aging, cardiovascular disease, and diabetes. The longevity benefits of exercise may be related to how it improves mitochondrial function and volume. Intense cardio exercise of HIIT and high volumes of aerobic exercise have different but complementary effects on the mitochondria in slowing aging.¹

Cardiovascular Disease. Low cardiorespiratory fitness is a strong risk factor for poor health and earlier death. Improving aerobic fitness improves cardiovascular health in various ways. For example, hearts typically begin to shrink and stiffen after the age of 30. Sedentary lifestyle is a risk factor for left ventricular stiffness. Intensive exercise regimes in fifty-year old men restore cardiac flexibility and functionality to that of thirty-year old men.²

Brain Health. Aerobic exercise improves cognition and may delay onset of dementia. It improves blood flow in the brain and thereby preserves arteries and capillaries crucial for oxygenation of brain cells. It also stimulates BDNF, or brain-derived neurotrophic brain hormone, which repairs neurons and dendrites, and stimulates growth of new neurons for short-term memory.³

Cancers. Aerobic exercise lowers risks for various cancers, in part by preventing obesity. One large-sample study found that exercise reduces the likelihood of dying from established cancers by 25 percent.⁴

Kidney Health. Exercise may help prevent chronic kidney disease by lowering systolic blood pressure and blood glucose and, at the same time, by lowering the risk for type 2 diabetes and cardiovascular disease. It may slow the progression of established chronic kidney disease for the same reasons.⁵

The Immune System. Many studies have shown that exercise strengthens the immune system and partially restores its youthful functionality. The common view that intense exercise depresses the immune system is questionable. The reduction in peripheral lymphocytes right after exercise, for example, reflects the temporary refocusing of the immune system on protecting internal vital organs at the expense of peripheral tissues.⁶  

Inflammation is a factor in many chronic conditions. Acute inflammation is part of the adaptive response to exercise, but in the long-term regular aerobic exercise reduces systemic inflammation, in part by reducing inflammatory cytokines from body fat. Exercise also inhibits mitochondrial dysfunction and thus inflammation by stimulating FoxP3 regulated T cells.⁷ 

GENES, MYOKINES, AND EXERKINES

Telomeres. Strands of genes or chromosomes are capped by protective telomeres. Telomeres shorten and become less protective when genes divide. Longer telomeres reduce mortality risk. High levels of exercise promote longer telomeres.⁸

Myokines and Exerkines. Myokines are signaling molecules released by muscles. Exerkines are signaling molecules generated by exercising muscles. Some myokines are exerkines. Through myokines and exerkines, the large muscles used in walking, running, and cycling communicate with tissues and organs throughout the body, signaling them to up their game. Some myokines and exerkines regulate longevity.  

The Cisd2 gene is one of most potent longevity genes. Its deficiency in mice accelerates aging and shortens lifespan, while high levels are associated with longer life. It is down regulated with aging, and upregulated with exercise; indeed, this effect is so strong that researchers suspect that the upregulation of Cisd2 by exercise may explain much of why exercise is so beneficial.⁹

The FoxP3 gene is a transcription gene, essential for making proteins. In its several polymorphisms, it is one of the genes most associated with longevity. It is involved in metabolism, regulation of cell cycles and harmful reactive oxygen species, and the elimination of senescent and dysfunctional cells. Large volumes of endurance exercise over many years are associated with elevated anti-inflammatory markers, maintenance of normal T-cell levels in the immune system, and higher expression of FoxP3.¹⁰

The KL gene encodes for the a-klotho protein. In Greek mythology, Clotho was one of three goddesses who wove the fabric of life. An anti-aging protein and exerkine, klotho inhibits disease in various organs, including muscles and the kidneys. It has anti-inflammatory and antioxidant effects and reduces calcified protein in the heart and kidneys. It is stimulated by exercise.¹¹

Taurine, another anti-aging protein upregulated by exercise, is associated with life-extension in worms, fish, rodents, and primates, and very likely in human beings as well. Food sources include fish, poultry, and meat from cattle and other wild and domesticated animals. Bodily taurine declines with age in all species. Supplementing mice diet with taurine extends life by ten to 24 percent.¹²  Many studies find that taurine benefits various organs in animal models and human beings alike, suggesting that it promotes longer life in human beings also.

The oxytocin gene encodes a protein that is processed into the hormone oxytocin, the love hormone. Oxytocin increases with love and exercise. It is anti-inflammatory and protects against stroke, neurodegeneration, telomere shortening, and the adverse effects of stressful isolation.¹³  Oxytocin also protects the heart by reducing inflammation and boosting metabolic and cardiovascular function. It can also help the heart mend itself by encouraging stem cell migration to cardiomyocyte lineages.¹⁴  The association of oxytocin with both exercise and love fits with evidence that the self-transcending effects of ultra-endurance exercise and adventure sports resemble love. Indeed, as we shall see, the distance running of early human beings was inextricably bound up with affection and connection in pair bonds, parent-child relations, inter-family relations and, beyond them, an intimate relation with nature.

MINDSET 

 

I have suggested in previous posts that endurance and adventure sports encourage flow, awe, and awakening, transcendental states in which preoccupation with the self is replaced by a strong sense of connection with others and the world. Many of the various traits associated with awakening—e.g., transcendence of the autobiographical self, connection with others and nature, courage, openness, curiosity, happiness, and compassion—have been found to be associated with health and longevity. ¹⁵

THE ANTHROPOLOGY 

 

Movement is a defining feature of animal life. In human evolution, it became especially important. Six to seven million years ago, when long-term drought in Africa reduced forested habitat for anthropoid apes, a group of apes came down out of the trees, broke off from the chimpanzee-like Last Common Ancestor, and began foraging on open ground. To protect themselves from an increased danger of predators in the more open environment and to maximize foraging, these early hominids became more social and cooperative than their chimpanzeelike cousins. Cooperation and sociability included pair bonding, which led to paternal recognition and care of offspring and ramifying kinship bonds between families. By 4.5 million years ago, these early hominids developed bipedal locomotion, which facilitated longer foraging treks and the carrying of babies, plant food, and game. The earliest human-like ancestors or Homo habilis emerged about two million years ago. Their brains were bigger, and they were becoming apex hunters, as evidenced by radioactive isotope traces of meat eating in their bones, stone tools, and butchered remains of large animals around campsites. It seems likely to me that they had begun to run in pursuing game that had been wounded in ambush.

Skeletal remains of Homo erectus indicate that skeletal structure and muscles had been reconfigured for persistence hunting or sustained running by 1.9 million years ago. In combination with loss of body hair and other features of improved thermoregulation, this suggests that “persistence hunting”—running game to exhaustion in the heat of the day—was becoming part of the hunt. 16  The observation that human beings differ from the apes in needing regular strenuous aerobic exercise to remain fully healthy makes this almost certain. ¹⁷  In addition to running game to exhaustion and thus making it easier to kill animals, fast walking and running would have been useful in getting to predator kills before other scavengers, and in beating them to animals that had been wounded in ambush. Although some commentators have doubted the validity of the persistence hunting hypothesis, the practice has been observed among modern hunter-gatherers in various parts of the world (use the hyperlink to The Great Dance: A Hunter’s Story below).

At some point, females developed menopause and both males and females began to outlive their reproductive years. Together, long-distance running and menopause eventually opened the door for the emergence of modern human beings about 200,000 years ago. They did this by ensuring the nutrient dense food supply required by offspring with larger, slowly maturing brains and by increasing the familial support or alloparenting available to parents raising bigger brained, highly dependent, slowly developing children. Human beings are the only primates capable of foraging on two limbs over longer distances well after their reproductive years, and they are the only ones who can hunt larger mammals or run long distances in the heat of the African sun. Menopause only occurs in human females and the females of some whales and dolphins. ¹⁸   

There is joy in movement (Image courtesy of Pasco County Schools)

 The upsurge of feel-good neurochemicals like endorphins, endocannabinoids, dopamine, and oxytocin during running was as much a part of selection for persistence hunting as were modifications of bone, muscle, and thermoregulation. ¹⁹   We are wired in such a manner that we not only experience “joy in movement,” as the psychologist Kelly McGonigal puts it, but also transcend the self in states of flow, awe, and awakening; we can feel deeply connected with others and the world, and in transcending self-concern and connecting with people and nature, we can grow in openness, curiosity, courage, and compassion, the very qualities required by an extremely social species engaging in long-distance foraging in a very dangerous environment. Accordingly, aerobic movement was a spiritual experience, intricately connected with the safety of the group and indebtedness to the supernatural. This pattern has been observed by anthropologists in recent hunter-gatherers. Such spirituality could involve mystical identification with game animals, a deep sense of connection with nature, and gratitude to supernatural beings for the beneficence of nature. ²⁰  Among the Kalahari hunter-gatherers, people often danced, sometimes all night, praying to God for rain and game. For the men, tracking and hunting were like “dancing.” They felt like they were becoming one with the animals they were following. Running was part of the hunt. They would run to get to wounded prey before the lions, hyenas, and buzzards. In “chasing hunts” they would run four to five hours in heat without stopping to drive big game to utter exhaustion. They would track while running without stopping. Tracking and dancing, they would say, made them “happy.” The experience almost surely involved flow and self-transcendence. Tracking and dancing, they would also say, “were like talking with God.” The Kalahari Bushmen danced, they said, to show “oneness” (See The Great Dance: A Hunter’s Story [The Great Dance]).

Average life expectancy in the Paleolithic was only 27 to 33 years but this average included high infant and child mortality due to bacterial, viral, and parasite infections. Demographic modeling from fossils and recent hunter-gatherer populations suggests that life expectancy after the age of 15 was comparable to that of modern populations. For those who lived to fifteen years, the average lifespan was about seven decades.²¹  Significantly, then as now, capacity for aerobic exercise in males and females across the lifespan was part of this extended longevity. Males and females are more equal in endurance activities than in sports requiring large muscles, and both genders are capable of jogging and running (and cycling) into their sixties and beyond (as anyone who has been in a gravel race can testify).

Throughout the mammalian order, large brains, long periods of infant and juvenile development, and longer lifespans tend to occur together. Human evolution took this complex to a new level by adding life after reproduction. Menopause freed females to devote more energy to gathering food for their families, and the longer lifespans and the ability of both men and women to walk and jog long distances allowed grandparents to help with the child raising of their children. These observations have led anthropologists to propose “father,” “mother,” and “grandmother hypotheses” to account for human longevity. By assuring survival of their children and grandchildren, parents and grandparents, according to these hypotheses, were improving their reproductive fitness by staying alive. David Lieberman and his colleagues put these hypotheses together with the “persistence hunting” hypothesis in an “active relagrandparent hypothesis” to explain not only human longevity but also the linkage between exercise and health. As they put it, “selection is unlikely to have favored longevity in unhealthy elderly individuals who were physically inactive because they would have been unable to forage, thus imposing energetic cost on caregiving relatives.” ²²  Lieberman and colleagues, in short, realized that exercise must have been a signal to the body that it should keep living.

By the Upper Paleolithic, foraging technology was increasingly sophisticated. Indeed, it required the same brain power now required by literature, poetry, music, higher math, and physics.²³ 

Learning habits of animals; the food and medicinal properties of plants; how to track; how to hunt with weapons, nets and traps; how to fish; knowing what was edible and what was not; where to find plant foods and how to prepare them; and how to make and repair weapons took, how to defend oneself and others against dangerous predators and how to cooperate with fellow hunters and gatherers required intelligence and took many years.

In my version of the active grandparent hypothesis, grandparents increased their reproductive fitness by foraging for their grandchildren and by passing on their skills and wisdom. In other words, exercise in foraging and care for loved ones signaled to the body that it could still contribute to reproductive fitness, that it was not yet time to die. Accordingly, studies have shown that loving and being loved along with exercise are among the most potent factors affecting health and longevity in human beings. ²⁴ 

I have ventured that no other species comes close to the cooperation and mutual bonding we see in human beings. This may be true enough of primates and other terrestrial mammals, but it is hardly fair to oceanic mammals. Whales, dolphins, and porpoises are stunningly consistent with our emended version of the active grandparent hypothesis.

Killer whales (orcas), short-finned pilot whales, belugas, narwhals, and to a lesser extent some dolphins also have long lives and live for many years after females have stopped reproducing. In addition, they are very much like us in being capable of ultra-distance movement, in having large brains, and being extremely social and affectionate. The brains of cetaceans contain specialized neurons that facilitate recognition, communication, problem-solving, memory, perception, and comprehension. Their emotional brains are larger than those of human beings, which suggests that they have unusual social intelligence, which is obvious enough just from their behavior. And they fashion and use tools despite not having hands and prehensile grips: they variously make waves that can knock seals off ice; intentionally stir up bubbles or mud to confuse prey fish; carry little fish in shells in their mouths; or protect their snouts with sea sponges. Whales and dolphins are self-aware and recognize others as individuals. They tutor their calves and juveniles during the long years of their development, and like humans they engage in “alloparenting,” that is, the caring of the young by other relatives in addition to parents. They cooperate in pod defense against predators, and they communicate with complex vocalizations in dialects that vary from one pod to another. Like human beings, they play throughout their lives. I once watched from a sea-side cliff as several dolphins were surfing off a Southern California beach. Were they experiencing the same delight that human surfers experience, the same sense of self-transcendence and oneness with the waves?

Whales and dolphins do not fight among themselves. When one pod of killer whales encounters another in a hunting ground, they avoid conflict with vocalization. Orcas are arguably friendlier to human beings than we have been to them. If we could speak their language, if we could know them personally, if we could swim long distances with them, would we want to commit them to solitary confinement for years on end or pollute their habitat with sonar, plastic, and toxic chemicals, or decimate their food sources?   

Among ancestral humans, long-distance foraging and care for younger generations signaled the body that it was too early to die, that there was still work to be done in provisioning and teaching children and grandchildren. All of us descend from those African ancestors. We are wired mentally and emotionally the way they were. Riding gravel, like other endurance and adventure sports, can rekindle the exercise physiology and transformative, self-transcending brain states of ancient foraging and communality. Accordingly, riding and racing gravel will probably lengthen our lives.

We are not living in the Pleistocene, however. We are in the Anthropocene, a time when human beings are adversely impacting the earth and its biosphere as never before. As the existential danger increases, the survival of our grandchildren depends less on what we do for them and more on what we are doing to ensure the livability of the planet for all children. As pastimes go, riding and racing gravel are a step in the right direction. They have a low carbon footprint and leave no trace. And I would like to believe that they can support the caring connections with others and nature that can counteract the environmentally destructive me-first preoccupations with wealth and consumption, and the mind-numbing virtual realities that are obscuring what is happening. Even so, bicycles by themselves will not prevent the impending catastrophe. If we truly care about the grandchildren, our cycling will have to become part of a life in which we once again move lightly, thoughtfully, and reverently on the earth.     

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1 J. R. Huertas, R. A. Casuo, P. Hernansanz Agustin, et al. Stay fit, stay young: Mitochondria in movement: The role of exercise in the new mitochondrial paradigm. Oxidative Medicine and Cellular Longevity (2019): https://doi.org/10.1155/2019/7058350.

 

2 E. J. Howden, S. Sarma, J. S. Lawley, et al. Reversing the cardiac effects of sedentary aging in middle age—a randomized controlled trial. Circulation (2018) 137: 1549-1560.

3 B. Cheval, L. Darrous, K. W. Choi, et al. Genetic insights into the causal relationship between physical acitivity and cognitive functioning. Scientific Reports (2023) 13. https//doi.org/10.1038/s41598-023-32150-1.

 

4 J. A. Lavery, P. C. Boutros, J. M. Scott, et al. Pan-cancer analysis of post-diagnosis exercise and mortality. Journal of Clinical Oncology (2923) 41:4982-4992.

 

5 H. Arazi, M. Mohabbat, P. Saidie, et al. Effects of different types of exercise on kidney diseases. Sports (Basel)
(2022) 10: 42.

 

6 J. P. Campbell and J. E. Turner. Debunking the myth of exercise-induced immune suppression: Redefining the impact of exercise on immunological health across the lifespan. Frontiers in Immunology (2018) April 16. Doi: 10.3389/fimmu.2018.00648.

7 K. Langston, Y. Sun, B. Ryback, et al. Regulatory T cells shield muscle mitochondria from interferon-y-mediated damage to promote the beneficial effects of exercise. Science Immunology (2023)8: doi:10.1126/scienceimmunol.adi3577.

8 M. Sellami, N. Bragazzi, M. Shaib Prince, et al. Regular, intense exercise training as a healthy aging lifestyle strategy: Preventing DNA damage, telomere shortening and adverse DNA methylation changes over a lifetime. Frontiers in Genetics (2021) 12: 652497.

9 Z-Q. Shen, Y-L. Huang, Y-C. Teng, et al. CISD2 maintains cellular homeostasis. BBA – Molecular Cell Research (2021): https://doi.org/10.1016/j.bbamer.2021.118954.

10 L. G. Minuzzi, L. Rama, N. C. Bishop, et al. Lifelong training improves anti-inflammatory environment and maintains the number of T cells in masters athletes. European Journal of Applied Physiology (2017) 117: 1131-1140.

11 H. de Luca Correa, A. Temizio Oppelt Raab, T. Marra Araujo, et al. A systematic review and meta-analysis demonstrating Klotho as an emerging exerkine. Scientific Reports, Nature Portfolio (2022) 12: 17587.

12 P. Singh, K. Collapalli, S. Mangiola, et al. Taurine as a driver of aging. Science (June 2023) 380, eabn9257.

13 T. Benameur, M. A. Panaro, and C. Porro. The antiaging role of oxytocin. Neural Regeneration Research (2021) 12: 2413-2414.

14 M. Jankowski, T. l. Broderick, and J. Gutkowska. The role of oxytocin in cardiovascular protection. Frontiers in Psychology (2020) 11: doi.1033389/fpsyg.2020.02139.

15. E. Seppala. The greatest and most overlooked secret to longevity. Psychology Today, posted April 29, 2013; N. A. Turiano, A. Spiro III, and D. K. Mroczek. Openness to experience and mortality in men: Analysis of trait and facets. Journal of Aging Health (2012) 24: 654-672; Y. Masui, Y. Gondo, H. Inagaki, and N. Hirose. Do personality characteristics predict longevity? Findings from the Tokyo

16. D. R. Carrier, The energetic paradox of human running and human evolution. Current Anthropology (1984) 25; 483-95; D. E. Lieberman. Human locomotion and heat loss: An evolutionary perspective. Comprehensive Physiology (2015) 5: 99-117; L. Liebenberg. Persistence hunting by modern hunter-gathers. Current Anthropology (206) 47: 1017-1025; M. Horo, H. Pontzer, M. Struska, et al. Comparing walking and running in persistence hunting. Journal of Human Evolution 172: https://doi.1016/j.jhevol.2022.103247.

17 H. Pontzer. Humans evolved to exercise: Unlike our ape cousins, humans require high levels of physical activity to be healthy. Scientific American (2019) January 1: doi: 10.1038/scientificamerican0119-22.

18 Humans and some certaceans are the only creatures who go through menopause in the wild. Some mammals outlive their reproductive years in captivity, however.

19 D. A. Raichlen. Wired to run: Exercise-induced endocannabinoid signaling in humans and cursorial mammals with implications for the ‘runner’s high. Journal of Experimental Biology (2012) 15: doi: 10.1242/jeb.063677.

20 R. Sands and L. R. Sands. Running deep: Speculations on the evolution of running and spirituality in the genus Homo. Journal for The Study of Religion, Nature, and Culture (2010) 3: 552-557; D. E. Lieberman, M. Mahaffey, S. Cubesare Quimare, et al. Running in Tarahuma (Raramuri) culture: Persistence hunting, footracing, dancing, and the fallacy of the athletic savage. Current Anthropology (2020) 61: 356-379; C. N. Forbes. The Primal Metaphysics of Becoming-Animal During the Chasing Hunt in the Kalahari Desert. 2020. California Institute of Integral Studies ProQuest Dissertations Publishing.

21 M. Gurven and H. Kaplan. Longevity among hunter-gatherers: A cross-cultural examination. Population andDevelopment Review (2007) 33: 321-365.

22 D. E. Lieberman, T. M. Kistner, D. Richard, et al. The active grandparent hypothesis: Physical activity and the evolution of extended healthspans and lifespans. PNAS (2021) 118: e2107621118.

23 Drawing on his work with Kalahari hunter-gatherers, Louis Liebenberg has argued that the origins of modern math and science can be found in the computational power required for persistence hunting and tracking: The Origin of Science: The Evolutionary Roots of Scientific Reasoning and its Implications for Tracking Science(CyberTracker, 2021).

24 A. J. Horn, C. S. Carter. Love and longevity: A social dependency hypothesis. Comprehensive
Psychoneruoendocrinology (2021): 100088.

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About the Author "John Ingham is 83 now and still riding, despite getting longer in the tooth. He is a retired--one might say, reformed--anthropology professor. He did research in a rural village in the central highlands of Mexico, and specialized in thinking about the interrelation of personality and culture, with passing interest in medical and biological anthropology. 

John has been drawn to adventure since he was a boy in Southern California. as a teenager, among other things, he did spearfishing trips to the gulf of Mexico and scrambled on local rocks. He has enjoyed running, skiing, wilderness canoeing, backpacking, cycling, and especially rock climbing and mountaineering. He gave up climbing eight years ago when his hands became too arthritic and took up gravel riding instead. Being way up there and way out there are about as good as it gets for him

He is married to Mary Grove. They have a son and daughter and three grandchildren, with a fourth, "little bro," on the way, ETA just after Christmas."