Why Did Grok Live So Long?

While I think the idea of adult Paleolithic hunter-gatherers regularly dying at age 30 can be laid to rest (sadly, I reckon that particular misconception has an impressive life expectancy), last week’s post on the Gurven-Kaplan paper brings up another question: if the human potential lifespan of 68-78 years, or roughly seven decades, is an evolved, inherent, even genetic trait, what is the evolutionary justification for its selection? Where is the advantage?

The classic Darwinian view is that selection of traits revolves almost entirely around fertility. Once an animal can no longer produce offspring, it has no “reason” to go on living. Since a genes’ survivability ultimately comes down to reproduction, whether an individual can have kids is the primary determinant of viability.

This makes sense when you look at the life cycles of various organisms. Lesser animals reproduce en masse, like spiders with hundreds of eggs in a single go or salmon with 2,500 eggs per kilo of bodyweight – quantity over quality. There’s very little, if any, mothering occurring with these types of animals. It’s just winning through numbers. They don’t have the capacity for socializing or organized communal child rearing; they just pump out as many kids/eggs as they can and hope for the best. Spiders typically die after spawning, and for Pacific salmon, spawning is usually the last thing they ever do. Their purpose in life – as laid out in their DNA – has been fulfilled. Their genes has been propagated, and there is, in the grand scheme of things, no “reason” for the reproducer to continue living. Further up the spectrum, reproduction becomes more of an ordeal and a sacrifice. It’s a general rule that mammalian pregnancy takes a lot out of the mothers; they must bear the fetus(es) for weeks or months, take in extra calories to sustain its growth and development, and eventually have their sexual anatomy ripped asunder by the act of giving birth. Larger or more complex mammals require more resources, more sacrifice, and more time committed. Canine pregnancies run about two months, chimpanzee pregnancies last around 220/230 days, and elephant pregnancies last about 22 months. Puppies nurse for ten weeks or so, while human infants (pre-formula) nurse for two or three years.

Humans represent the pinnacle of mammalian complexity. If they are regularly living past reproductive age and consuming resources that could otherwise go to younger, fitter, more virile members of the group, there must be a reason for it. The original assertion – that an organism’s fitness depends on its contribution to its genes’ survival – holds true, but the complexity of the human animal requires an expansion of the original idea. These old folks must be contributing to the success of the gene through non-reproductive means.

The obvious answer is the “grandmother hypothesis” – the idea that post-menopausal women can provide their children and grandchildren with a better chance to breed, and thus further contributing to the survivability of their own genes. Unable to reproduce themselves grandmothers care for little ones while the immediate parents are out gathering or hunting (or working a job in modern terms). Once that last batch of kids has reached young adulthood, at around age 15 when they can begin fending for themselves, the grandparents are no longer “needed.” The young adults are ready to start producing for the community and having their own kids, thus ushering in the new wave of grandparents (the young adults’ parents). The first set of grandparents, now beginning to hit age 70, can pass away without negatively affecting the genes’ survival. They’ve done their part and contributed to the survivability. There’s no longer a need for even more longevity. It all sounds pretty morbid, but that’s how this stuff is hypothesized to work. There’s also something called the “mother hypothesis,” which is similar to the grandmother hypothesis, except it explains human longevity by positing that if mothers have their last child by age 45 or so, they’re stuck raising the child until age 60 or 70. Both are valid and viable ideas, and I think both can coexist.

But what about grandfathers? A long-standing criticism of the mother and grandmother hypotheses is that no explanation is given for the longevity of the elderly male. What can Gramps contribute to society, and why does he live past the viability of his sperm?

Kaplan, Lancaster and Robson propose the “embodied capital” model of human longevity to encompass both sexes. Simply put, it suggests that male and female human longevity is necessary because of the slow, long development of human children. We aren’t like most mammals, who tend to spring forth from the womb with the ability to walk (or swim) and avoid embarrassing themselves; our infants are immobile fleshy bundles. Our children need guidance and instruction from our elders. They need support – the community needs material support, since the children consume resources without providing any. And both grandma and grandpa are involved in the teaching process. The emphasis here is on passing on knowledge and wisdom. They’re not just chasing little ones around.

We can’t survive on instinct alone. Our physical gifts aren’t sufficient. And we don’t pop out of the womb with knowledge and wisdom pre-installed. We come out with empty heads full of potential. We have to learn, or, more accurately, we have to be taught. And who teaches us? Experience is a stern, proven tutor, but exogenous instruction from experienced adults, parents, and grandparents – from society, really – is even more crucial. We need adults to live past reproductive age because human children are unproductive members of society for at least the first 12-15 years of their lives. They are either totally helpless babies (unable to walk, talk, and procure food), extremely annoying toddlers (now able to walk, babble, and get into trouble), or haughty mischief-making pre-teens. And all the while, they are students. They’re learning, watching, observing, and filling their big empty brains with the knowledge and experience that will help them be productive, resourceful adults. But they couldn’t do that if all the adults were dying off by age thirty.

While kids learn, work must be done. The animals must be hunted, the food must be gathered, the crops (if they’re horticulturalists) must be tended. The daily chores for a hunter-gatherer community require physical strength and know-how. Hunting requires endurance, precision, and fearlessness, which kids have little of. Gathering means carrying heavy loads, digging, climbing, and walking long distances. Kids undoubtedly accompany adults on outings (to learn, remember), but they cannot be expected to provide for the group. Adults aren’t just teachers, then. They’re also material producers. They hunt, fish, gather, build, carry, defend, and explore – all the nuts and bolts stuff that makes a society go.

Humans are animals, true, but a special kind of animal, one that has expanded the standard definition of evolutionary fitness. And no, I’m not trying to imbue our species with some sort of cosmic or spiritual significance; we create our own significance, our own meaning, by virtue of our massive brains. That’s the point. Our brains provide our consciousness, and, for all intents and purposes, set us apart from even our closest, brainiest cousins in the animal kingdom. Our tendency toward higher thought also allows us to exert mastery over nature. We plan. We study. We learn. We can develop the ability to spear a moving target – an ability that relies on our mastery of the physical and the mental realms. Hand eye coordination, spatial visualization. Memorization of the properties of thousands of wild plants – which are poisonous, nutritious, medicinal? Instinct and the subconscious save our rear ends in times of acute trouble, but our careful, measured intelligence and rationality puts us at the top of the food chain. We couldn’t take advantage of our brains without the security and dependability of having older humans around to teach us, train us, and support us. The kids may be the future, but adults set the path.

To summarize:

  1. In most hunter-gatherer/traditional groups, human lifespan extends past fertility. This indicates that elders contribute to the success of the group.
  2. Grandparents act as caregivers for children and grandchildren. Once the last set of grandchildren reaches maturity, older adult mortality rises, indicating that the grandparents’ “job has been done.”
  3. For the first fifteen years of their lives, children are information sponges. They’re learning how to be productive adults from productive adults, and they are physically immature and unable to keep up with heavy labor; until the children’s “formal” instruction ends and they become productive members themselves, the adults must provide material support for the group.
  4. Adults, especially older adults, act as knowledge reserves. The kids have to learn from someone, and elders are a powerful source of information. This role benefits the group by enabling the transformation of children into productive members of society.
  5. “Respect your elders” isn’t just a line thrown out by cantankerous grandfathers; it’s embedded in our hunter-gatherer past, and it might be the key to our species’ unparalleled success.

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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35 thoughts on “Why Did Grok Live So Long?”

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  1. It all makes sense when you remember that the genes will code for any trait that will increase the propagation of those same genes. It makes sense that both old men and old women have valuable contributions to make to their own descendants’ survival, especially in traditional societies where their skilled knowledge is not obsoleted like it is in modern technological societies. Also, the fact that men live roughly as long as women could easily be explained by the fact that men remain fertile into old age; perhaps women live a long time to take care of grandchildren, while men live just as long in order to have a chance of fathering that last child at age 65. Plus, in hunter-gatherers, old men typically were still very fit and can still make real contributions to hunting and other work.

  2. One more major loss to CW. Grandparents now are just ‘old, messy people we don’t want to deal with’ and get locked away in nursing homes. It would be so great if we could bring back the multi generational household. Doesn’t even mean you have to share the SAME house but it sure would be nice if kids, parents and grandparents all lived very close together and shared more parts of DAILY life.

  3. read Jared Diamond’s “Why is Sex Fun” to gain a more thorough understanding of the relationship between human lifespan / sexuality / evolution.

  4. This explains a lot, a lot of what’s wrong with industrial capitalist life: kids aren’t with their parents or grandparents; they’re locked up in schools, away from the real world, learning very little. Grandparents typically don’t live near their grandchildren.

    When kids become adults at 18, they suddenly have to figure out how to work and take care of themselves, something they’ve been protected from for 18 years.

    I teach college students, and I can’t figure out what they spent the last 12 years doing. Most of our students can barely read and write, and they don’t have any “real life” skills either. About all they can do is operate their cell phones and watch YouTube videos on their computers.

  5. Getting pretty geeky around here lately, death, feces, intestinal bugs..

    Love the recipe ebook to balance things out.

    How about a post with primal insight on the twinkie diet Mark?

    1. No post needed, as it is simply a starvation diet.

      If that cruise ship would have been stranded a bit longer, we’d be hearing about the Spam & canned crab diet.

  6. Mmm, and I think we are now devolving because we have blocks of population who are unemployed, demotivated, incapable of critical independent thought; their children are not in a rich environment to learn life skills, they just learn to be dependent, demotivated unemployed people and grandparents are nowhere in sight.

    Society seems to be in a complete mess.

    How will that impact on ‘natural selection’? Have we completely neutralised the very mechanism that brought us this far?

    1. Being blog fed too much re-meta analysis of yet someone elses work will do that to people.

  7. Thanks for the post Mark. This is something I’ve always wondered about and your explanation makes a lot of sense. I really enjoy the geeky, evolutionary explanations/musings. For anybody out there that hasn’t read The Naked Ape Trilogy by Desmond Morris, I highly recommend it. He was thinking this way back in the 60’s.

  8. I love how this concept gives real value to grandparents and older people. We live in a society that worships the young. I it is nice to know that the older person has an valuable role to play.

  9. I truly believe that multi-generational living is something meaningful that we are missing out on these days. Don’t get me wrong, I was raised to be independent early on, and the LAST thing I would want is to live with my parents..*shudder* but, it wasn’t too long ago that families stayed together…the old ones cared for and taught the little ones, the middle ones cared for the elders, wisdom was passed on…I do think this was most beneficial to the species…and now look at the Long Term Care Nursing Home Debacle, newborns in daycare, kids don’t know their family’s history..nevermind the basics, like work ethic, morals, etc..
    I was lucky enough to have 2 great grandmothers who lived well into their 90’s that I was close to, and only recently lost one of my grandmothers. (I am 37) I held her as she lay dying as she held me in my infancy…The circle of life…
    I appreciate every word uttered from those wise women’s lips…especially at this difficult time in my life. Thanks, ladies…xoxo

  10. Great article and comments. i liked what Dawn and Shannon said. I try to teach my kids to respect their elders and they know better than to ‘dis’ old people because they get an earful from me. We spend some time with the older members of our family and we use to spend alot of time with elderly people before we changed countries and I found them a good source of information and inspiration and I try to pass the stories on to my kids because we don’t always have our old people around. I do have to laugh though when I see them listening for hours to my dad and his stories (without rolling their eyes once!)and they can barely sit still for 5 seconds to listen to ‘sound instruction’ from me. But ultimately they are good kids and I can only hope that they will be an asset to society not a menace as we a seeing alot of these days.

  11. Sorry went off subject a bit with my last comment but just a thought I had. Would it be right in saying that maybe once grandchildren arrive grandparents now have a new ‘reason for living’. From what I’ve seen the older generation seem to have a sense of unselfish sacrifice sadly I don’t think its genetic.

  12. My dad taught my kids to lick their plates clean, literally. I suppose that gave them a tiny extra boost of nutrition.

    1. LOL!! thats funny! my mum let us lick our plates when we were kids (still do sometimes when we eat at their house!)and that was because she was NEVER allowed to when she was a kid. My husband still can’t get over it even after 15 years of hanging out with us.

  13. I completely agree that children brought up with grandparents and extended family helping to care for them as opposed to daycare with multiple children and high turn over of staff have a much richer environment, more one on one learning, stronger values and a host of other benefits. Not to mention it leaves the parents financially better off as daycare is expensive, which I am sure would mean less working hours for the parents and less stress in general.

    That said, Mark mentioned that most animals that have huge numbers of off spring, like salmon and spiders and what have you, have shorter life spans because their main purpose is to propagate the species with quantity over quality. Which makes me wonder about sea turtles? Don’t they have hundreds of eggs at a time but live as long as 100 plus years old? DO they have “family structure”?
    According to the Discovery Channel/Animal Planet type shows, elephants have the longest gestation period of any animal, but they do have a family structure in their groups that play a grandmother type role, even sometimes a designated midwife who helps other females when they give birth.

  14. Beautifully written. A great reminder that our seniors are a valuable treasure, not disposable has-beens. Thank you.

  15. It’s really only in our society that kids are unproductive. 200 years ago- or now, in third-world countries- children are definitely productive. They do farm work, take care of the younger children, cook, clean, at a remarkably young age.

    1. Oh yeah but in the ‘modern western world’ its almost classed as child abuse if you make your kids clean their rooms or actually do some manual labour for free!
      My kids have been taught how to do all those kinds of domestic chores but the older they get the more I have to ‘get on their case'(patiently) to do their part but they are actually very good at it once they get going!Its a shame when you see teenage kids who don’t know how to cook or do any basic cleaning these are the skills that will help them later in life when/IF they move out on their own or even just to help their parents/grandparents.

  16. One quality, more than any other, defines human beings as an elite survivor – the ability to create, replicate, and disseminate sophisticated memes. Tracking game, building tools, traps, and shelter, preserving food, navigating terrains, forecasting weather, identifying edible plants or healing herbs, all examples off the top of my head.

    Simply being old in paleolithica implies that you are an expert survivor. Even without the ability to pass on genes, tribal elders still possess the most valuable memes through accumulated knowledge and endless practice. These memes vastly improve a tribe’s chance for survival, and in turn translating into an evolutionary advantage that propagates genes for longevity.

    I do want to say that I don’t think this same evolutionary edge really carries over in modern society. In fact, in an age when people live longer than ever, it almost seems like old people have less value now than at any other point in our history.

  17. Technology has really screwed up this process of passing down information. Many grandkids have taught grandparents how to respond to a blog post using a smartphone.

  18. Our steroetype of “grandparents” is furthered the same way CW has furthered our “health”. Paleo Grandparents were probably more robust than our middle aged people today,which isn’t saying much.

  19. Guess there are a lot of “grass is greener” posts here. If my grandparents were full of wisdom, I would visit them more often 😉 But since their offspring so often seem to be grown-up kids with salary, I don’t want THAT kind od wisdom for myself. And I guess many, many more people don’t have respect for their parents and grandparents, because respect has to be earned ^^ And I see that everywhere

  20. This is something I have spent a lot of time thinking about as I am an academic sociologist.

    My guess is that it comes down to culture (which is what you more or less said). Humans don’t evolve as individuals, they evolve as social groups. Our physical gifts are kind of pathetic compared to the other animals. So we get by on our shared survival knowledge – our culture. As such, the oldsters carry a lifetime of knowledge around that helps us overcome with culture evolutionary problems that would stump us individually and physically.

  21. Nice post, but “unparalleled success”? You can’t really go past ants for that.

  22. I thik all this information is helpfull in understanding the primal pholosophy. I am disappointed however that you are contributing to the maintenance of the myth that learning is about filling an empty vessel (the brain). Learning is a social process in which ‘learners’ take, make and give meaning to the world around them. This is why each of us will TAKE only part of what we read in this blog, Make meaning with it as we process it along with passed knowledge — yes, even a child born an hour ago has previous knowledge, the brain is involved in the birthing process — it we participate on this blog or discuss what we have read with others we continue the knowledge making process as we GIVE new meaning/knowledge to others. If learning was a one way street — from the elder to the younger — evolution of thought, tools, etc. would not be possible.

    Consider this, children are responsable for the introduction of new words and meanings into languages worldwide. If this was not so, we would all speak a language similar to that of our primal ancesters did and thereby not be able to have this conversation and, quite possibly, have conversations that would make no sense to us in the modern world.

    Children’s brains are not empty!

  23. I read somewhere that the inuits put their old folks on a piece of ice to be floated off into the ocean.

  24. Grandaddy Grok’s fertility into old age could have influenced the longevity of both his male and female progeny. He would have been passing on good old age genes to both genders.

  25. So it’s geneticaly programmed in our DNA that if where old and our grandchildren and children dont need us anymore we will drop dead?

  26. What if you have other reasons to live beside children/grand children?

  27. “cantankerous grandfathers”
    lol, Mark, where do you store all these awesome words? Must be those crosswords you do with your morning coffee!!!

    Great post, I’m happy you put it in the time capsule! 🙂 I think humans just evolved to be a cut above other species, so much we are radically different from other animals; philosophy debates on “I think/am therefore I am/think” nonwithstanding, we are being of reason, not just driven by carnal instinct (though occasional hedonism is very Primal. *hand reaches into bag to retrieve slab of dark chocolate*)