Thursday, February 4, 2010

Paleo Life Expectancy

Critics of paleodiet often claim that Paleolithic people died at 30 years of age or similar young ages, and suggest that this proves that paleodiet (basically, a grain-, legume-, sugar-, and dairy-free diet) does not support health or longevity. 

I would like it if these people would provide some evidence that meat, vegetables, fruits, and nuts lack some  critical nutritional factor necessary for longevity and found only in agricultural foods -- grains, legumes, sugar, or milk.  I do not know of any such factor. 

In fact, we can state certainly that paleolithic diets supplied humans with all the nutrients humans require, because if they did not, the human species would have expired due to malnourishment.  Further, as I showed in my post Primal Diet On A Shoestring, a paleo diet composed of modern foods can easily supply required nutrients.  This means that even if paleo people did have a short life expectancy, it was not due to some nutritional weakness of the paleolithic menu.

I consider the idea that paleo people died at 30 years of age (or so) a “just-so” belief derived from the stories that Mother Culture tells us.  I have never seen any evidence to support this claim.  On the contrary, critics commonly present this as something “everyone knows.”   So, how does “everyone” know this?  They learn it as a part of a pack of stories we get told about preagricultural people, all expressing the Hobbesian claim (made without evidence) that human life in the absence of agriculture and the State was “nasty, cold, brutish, and short.”

In short, "everyone knows" this the same way that "everyone knows" that cereal grains are essential to nutrition -- it is not knowledge, it is simple mythology.

As a matter of fact, we have evidence that hunter-gatherers had low adult mortality rates and achieved ages comparable to civilized people, despite the absence of the legendary longevity powers of agricultural foods and the tyranny of the State.



Recent Hunter-Gatherer Evidence

According to Between Zeus and Salmon: The Biodemography of Longevity, a publication of the National Academy of Sciences Commission on Behavioral and Social Sciences and Education (National Academy Press, 1997) (pages 176-179):


"The most reliable estimates of adult mortality rates available for a pre-contact hunting and gathering group are derived from Aché research (Hill and Hurtado, 1996), because of the research focus on producing accurate measures of age and accounting for all adults that lived during the twentieth century."

So what can we learn from the Aché?

Well, among them, 30-40% of people die before the age of 10-15 (most of these before 5). 

These early deaths draw down the average lifespan in hunter-gatherer tribes.  To simplify the mathematics, if you have a cohort of 100 babies, 40 of which die before 10 years and 60 of which die after 60 years, the average life expectancy for this group will fall under 40 years, despite 60% of the population living more than 60 years.

Among both ancient and modern hunter-gatherers, these and most adult deaths occurred from hazards of childbirth, infections, accidents (e.g. falling from a tree, drowning, etc.), animal attacks (insects, snakes, etc.), poisonings (toxic plants), inclement weather (floods, snowstorms, etc.) and other dangers affecting all age groups but especially children growing up in a wild environment.  They did not occur from diseases of civilization, like heart disease, cancer, diabetes, and the like.

Among the Aché, once people passed puberty, in the adult age range of 20-45 mortality rates appear low, about 1.5% per year.  In comparison,  adult wild chimps have a mortality rate of 7.9% per year.  The text states:

“Adult mortality rates remain low and do not rise significantly until the seventh decade of life, where the rate climbs to 5 percent per year and reaches 15 percent per year by age 75.”

This text supplies the following graph of the age-specific mortality rates among the Aché:
 
Aché age-specific probability of death, smoothed with logistic regression.

From this you can see that among the Aché, children under 10 and adults over 60 years of age have the highest death rates.  Some Aché people live into their 7th decade of life, despite lacking the assistance of civilization.  Males have a higher mortality rate than females due to accidents in hunting, more testosterone-induced reckless behavior,  and possible altercations.

This text also provides the following graph comparing probablities of surviving to ages up to 80 years among several human tribes--!Kung, Yanamamo, Aché, and Hiwi -- and wild chimpanzees at Gombe:


 
Age-specific probabilities of survival among human foragers and chimpanzees. 

You can see that wild humans can live about twice as long as wild chimpanzees, even have a chance of living past 80 years.  Regarding this data, the text states:
"Although sample size and methods of data collection vary among the four human groups, the survival curves show remarkable convergence, Although infant mortality rates vary, with Hiwi being the highest and Yanomamo the lowest, adult mortality rates between the ages of 20 and 45 are almost identical, about 1.5 percent per year. For that reason the survival curves are parallel to one another during the adult period. Chimpanzee survival curves, however, diverge dramatically from the human curves, due to a quite distinct adult mortality profile. For example, while both Hiwi and chimpanzees have about equal probability of reaching age 15, the conditional probability of reaching age 45, having reached age 15, is near zero for chimpanzees in the wild and about 75 percent among the Hiwi."
So modern hunters live well past 45.  What about ancient people?

Migration and Population Expansion Evidence

In preagricultural times (between 50, 000 and 10, 000 years ago), humans migrated out from Africa around the globe.  By 10, 000 years ago, humans had reached and populated the Americas.  Given human reproductive function, this could not have occurred if people died at 30 years of age.

In The Paleolithic Prescription, S. Boyd Eaton, M.D., Melvin Konner M.D., Ph.D., and Marjorie Shostak present data on reproductive milestones among recent hunter-gatherers.  Among three recent hunter-gatherer tribes (Agta, !Kung, Ache), the average age of menarche (onset of menses) is about 16 years of age, the average age of first live birth is 19.5 years, the average birth spacing is 3.45 years, and the average number of live births per woman is between 4 and 5.

In order for the human population to grow to populate all continents over the period 50K to 10K years ago, each woman (on average) would have had to have had more than 2 children who made it to adulthood and reproduction.

Taking the first live birth at 19.5 years,  an average birth spacing of 3.5 years, and a 30-40% mortality rate for children under 15, we can see that the average paleo woman had to live at least 60 years in order to see a growth in the total human population.

Lets do a thought experiment.  Say Patty Paleo has her first birth at 19.5 years of age.  This child, named Peggy Paleo will have a 60% chance of making it to adulthood.  If Peggy does make it to adulthood (menarche), Patty will be 35.5 years of age when Peggy first menstruates, and 39.0 years of age when Peggy has her first child.  Since Peggy will have to learn how to birth and care for a child from Patty, Patty will still be largely essential to Peggy’s survival until 39 years of age.

Patty Paleo will have her second birth at about 23 years of age.  If this second child, Rick reaches physiological adulthood (capable of reproduction, 16 years of age), Patty will have reached 39 years of age.

Two births only replace Patty and Paul, the parents of Peggy and Rick, assuming that both Peggy and Rick make it to adult hood.  Let’s say that Peggy and Rick do make it to adulthood.  To expand the population, Patty has to have at least a third child and raise it to adulthood.  So Patty has her third child, Darth, at 23+3.5=26.5 years of age.

Since about 1 in 3 children die before adulthood among the Aché, our thought experiment should include this aspect.  We will imagine that Darth makes it to 4 years of age, then dies of a snake bite.  Patty is now 30 years of age, and has her fourth child, Star. 

Patty will spend the next 16 years raising Star to adulthood, at which time Patty will be 46 years old. 

Data collected on the !Kung indicates that the average !Kung woman has 4 to 5 live births during her reproductive lifetime, with the last birth occurring in the woman’s third decade of life [1]. Therefore, we can imagine that Patty has a fifth child, Apogee, at 33.5 years of age.  Apogee will  reach 16 years of age, when Patty reaches 49.5 years of age.

The Menopause Evidence

Further evidence that paleo people, at least women, reached ages well beyond 50 years of age exists right now in the phenomenon of menopause, a reproductive milestone unique to humans among primates (elephants also have a menopause, and can live 70 years in the wild). 

According to evolutionary theory, menopause would not exist unless it conferred some survival advantage for offspring.  The fact that human females go through menopause around 50 years of age tells us that our ancestral mothers did in fact make it to 50 years and beyond, and that those mothers who ceased menstruating at about 50 years of age left more offspring (children and grandchildren) than those who continued to menstruate.  

In short, the fact that present-day human females go through menopause provides living testimony that our prehistoric ancestors had lifespans greater than 50 years, and that paleo people who lived more than 50 years made their offspring more successful (reproductively).

Photographic Evidence


Of course I could have simply showed you this photograph of Chief Seattle, a lifelong hunter-gatherer, made when he was somewhere near 85 years of age. According to the Wikipedia entry on his life, the Chief was born about 1780, and this photograph dates to 1865.





Clearly, those who say that paleo people didn’t live past 30 just don’t know the subject well enough to have an opinion.

For more on this topic, read Ron Hoggan’s excellent article, Life Expectancy in the Paleolithic.

P.S.  If you like this post and want to see more like it, please consider making a small donation or a recurring subscription payment using the PayPal buttons in the right hand column.  Fighting fallacies is a full time job I love to do, but I need support to continue doing it.  Also consider sending a link to this post to all of your Facebook and other friends.  



Notes:

1.  Frisch RE, Fatness and Fertility, Scientific American 1988 Mar;258(3):88-95.

29 comments:

O Primitivo said...

Hi Don, thanks for this excelent and informative article. There is an interesting article with detailed mortality data from an isolated, traditional portuguese population from the Azores, at Pico Island. Here is the link to the article: http://dialnet.unirioja.es/servlet/articulo?codigo=1153353 (you must click Descargar) You can see from page 58, Quadro 1, that, for people born between 1740 and 1799, life expectancy at birth was only 50 years, but once you reached 20 or 30 years old, life expectancy would be the about 70 years or even more. Yes, this was in the 18th century, two centuries ago, in an isolated island in the Atlantic ocean, when there was no modern medicine! In the next page of that article there is data for the 19th century, showing increased life expectancy at birth due to lower child mortality, but once you reach the 60 years old or more longevity was very much like in the previous century. I suppose primitive people would have very much these same longevity/mortality patterns, or do you belive there are reasons it would be too different from this? There is another portuguese article, with more recent health trends, but from continental Portugal, not the isolated island of Pico, that shows that in 1920 women's life expectancy in Portugal was only about 40 years old. In the 50s, it was better, 53 years old (see page 17 of this article: http://www.krepublishers.com/02-Journals/JHE/JHE-22-0-000-000-2007-Web/JHE-22-1-000-000-2007-Abstract-PDF/JHE-22-1-015-07-1518-%20Padez-Cristina/JHE-22-1-015-07-1518-Padez-C-Tt.pdf). I think we can draw some interesting conclusions from this data, but this comment is already too long, so I stop here. Here is the english abstract of the first paper I quoted: "The mildness of death in the island of Pico, namely in what concerns the length of old age, is a unique phenomenon. One may well associate it with the mildnessof the climate, fairly dry, with pure waters, a varied diet, based on maize cake but consisting also of sweet potatoes, not much meat, fish, milk and its derivatives, some wine and plenty of fruit. Genetic factors may account for the high rate of survived of the inhabitants of Pico, but their isolation has also preserved them for long from epidemics. In the 18th century, breast feeding until late childhood may have avoided infant mortality, though children were vulnerable to the cold weather. If on the one hand the 19th century brought an improvement in the domestic conditions which favoured the survival of children and adults, on the other evolution of cultural ways and customs burdened children to some extend, along with the smallpox epidemics common in that century. We should bear in mind that only in the 1940s were the positive effects of external resources to help survival traceable in the island."

Miki said...

Don
Excellent post. This point of presumable short lifespan of HG comes up like a clock every time the subject of plaeo type diet is discussed with the uninitiated.
Kaplan et al. (http://www.anth.ucsb.edu/faculty/gurven/papers/GurvenKaplan2007pdr.pdf) use a parameter called Modal Age of Death (MAD), which is the age most people die, to compare a number of HG groups with 2002 Americans. It is most interesting that while chimpanzees have MDA in captivity of 45 years compared to 15 years in nature, the Americans' advantage over HG's is a mere 12%. We may have much more potential for extended longevity in paleo type diet and lifestyle than we realize. May be not 200% but 20% will also be nice.

zach said...

What plant has more nutrition than any pastured organ meat, or, say and egg? Case closed.

haus3287 said...

Hi Don,
Excellent post! I would like to present an alternative explanation for the advantage of menopause. Menopause occurs, in healthy women, because they actually run out of oocytes. In order to produce more eggs, a woman would have to have larger ovaries, which would require more energy, hence more food, starting at birth and even before (the number of oocytes is fixed before birth). The energy differential would increase at the onset of puberty, when the ovaries enlarge. This could create a survival disadvantage for a "large ovary" woman during her entire lifespan, whether or not she lived to age 50.

Regards, Ed

Richard Nikoley said...

Stephan did a post on Inuit mortality about a year.5 ago:

http://wholehealthsource.blogspot.com/2008/07/mortality-and-lifespan-of-inuit.html

Don said...

O Primitivo,

"I suppose primitive people would have very much these same longevity/mortality patterns, or do you belive there are reasons it would be too different from this?"

No, I don't think it would be much different.

Ed,

What I said and you propose appear compatible to me...a woman with higher energy requirements due to larger ovaries would have a disadvantage in reproduction and leave fewer successful offspring. Since gestation increases energy requirements, the combination of large ovaries and gestation would increase pregnancy energy requirements, making it more difficult to carry to term.

Richard,

Yes, anyone who thinks paleo people died young can also benefit from a read of Stephan's post on Inuit mortality.

Ned Kock said...

Very good and timely argument.

Women are really the bottleneck of selection, and I suspect men carry several genetic mutations that are health-enhancing because of the selective pressure on post-menopausal women that you alluded to.

Since older paleo women contributed to enhancing the survival success of both offspring AND grand-offspring, selection pressure for longevity among post-menopausal women might have benefited the whole species.

This is due to the gene correlation phenomenon. Some genes that evolved due to selection pressure in one sex are present in the other, leading to the expression of traits that may be more or less beneficial to the other sex as well. (The men-have-nipples effect.)

Two interesting factoids related to this: (a) women typically live longer than men; and (b) in populations under harsh environmental circumstances, female births increase in frequency, sometimes dramatically.

Jeffrey said...

Life before agriculture and government WAS brutish and short. In fact, it was a state of perpetual anarchy. That they may have eaten better than we is no reason to deny the profound benefits of civilized society.

Don said...

Ned,

Thanks for the additional info. Female births also increase with vegetarian diets. I believe this arises because male embryos, under the influence of testosterone, have a higher energy requirement. Thus, restricted diets favor the birth of the sex that has the lower energy requirement.

Jeffrey,

Life before agriculture was not brutish nor short (which I just showed). I suggest reading some accounts of life in hunter societies, like The Old Way by Elizabeth Marshall before you just regurgitate social myths.

http://donmatesz.blogspot.com/2010/01/plant-foods-in-kung-diet.html

Not only humans but several otaher species live long lives in the wild, including elephants (70 years+) and whales (some live more than 100 years).

http://en.wikipedia.org/wiki/Maximum_life_span

Yes, it was "complete anarchy", but anarchy does not mean chaos as you imply/imagine, it only means "no ruler." No ruler (no one in charge) does not mean chaos either. Nature is not chaotic despite having no ruler.

Christopher Ryan said...

Right you are, both on the facts and the importance of this misinformation. What I find particularly interesting is the longevity of demonstrably false ideas that make people feel good ("We've doubled the human life-span!"). We have a chapter on this issue in our soon-to-be-published book about the sexuality of prehistoric hunter-gatherers (Sex at Dawn, HarperCollins) called "The Longevity Lie" where we look both at the data you present here and the underlying motivation for repeating it. Unfortunately, you're too generous in saying it's just the uninformed who do this. Archeologists, anthropologists, physicians . . . many people who know better repeat the comforting lie.

Lilmissinn0c3nt1 said...

I don't know much about the hunter-gatherer lifestyle but if diet is the main concern for life expectancy what are people saying about medicine and such these days? I thought that a decent amount of people would die at early ages in the past due to disease and illness caused by bacteria's we now have under control or that are easily treated? Do the medical advances of today help support that the life expectancy for someone with this lifestyle is hardly effected by the diet, simply because of the medical advances, places and people in general being cleaner?

Breukellen said...

I agree with Jeffrey in the sense that this data does seem to prove that life was short and brutal for children under the age of 10, and child-bearing women. Make no mistake that pregnancy was and still is a life-threatening condition. That said, I appreciate the arguments for a paleo diet. I've mostly embraced a paleo diet without even knowing that's what it was. That doesn't mean that I don't plan on going to a good OBGYN and giving birth in a hospital with all the necessary precautions. Obviously, we all enjoy modern technology, as this is posted on the internet :) We are lucky to have the luxury to pick and choose the beneficial aspects of hunter-gatherer life, while still having access to modern technologies which also benefit our lives.

Ross said...

This is an excellent post which mirrors many of my own arguments. When you understand cause of death, you can separate death due to environmental hazards and acute health issues (childbirth) from death due to senescence or chronic ill health.

Without such a separation of confounders, the assertion that the average lifespan of our hunter gatherer ancestors was only 35 provides no insight or useful information, even if true.

Don said...

Those of you who think paleo life was brutal but modern is not seem to ignore the fact that agriculture and civilization brought war and unprecedented starvation. You may live in the U.S. or other "protected" nation. Take a trip to Africa, Southeast Asia, Afghanistan, etc. to see the brutality of agricultural existence -- the relative "safety" and wealth of EuroAmerican nations being founded to a large extent on colonization and corporate exploitation of the "developing nations" in which war and starvation are prevalent.

I doubt anything suffered by paleo people can count as more brutal than modern warfare. Dropping nuclear bombs on people is not brutish?

As I pointed out in the GOE, "Already an unprecedented 3 billion people are malnourished. Infections and pollution, both side effects of overpopulation, cause 75 percent of deaths each year."

You might also read Michael Eades post titled "Nutrition and health in agriculturalists and hunter-gatherers" which provides some of the evidence that early agriculturalists had more disease and shorter life expectancy than hunters:

http://www.proteinpower.com/drmike/low-carb-diets/nutrition-and-health-in-agriculturalists-and-hunter-gatherers/

Don said...

Breukellen,

Hospital births aren't necessarily safer than births attended by an experienced midwife.

http://www.ncbi.nlm.nih.gov/pubmed/9271961

In fact, this study found more medical interventions in the hospital births, but no significant difference in perinatal mortality. Home birthing mothers had a lower incidence of severe lacerations. Myths about the efficacy of modern medicine abound.

Don said...

Christopher,

Looking forward to reading your book. I know, even people who we might expect to know the truth spread the lie... their professions depend on maintaining the illusion that their "knowledge" keeps us healthier, living longer, etc.

Breukellen said...

Don,

Last sentence: "Home birth is an acceptable alternative to hospital confinement for selected pregnant women, and leads to reduced medical interventions."

It is only through modern medical technology that we are able to determine who might be on of those "select" women.

I don't see the harm in having emergency equipment nearby, because even in low risk pregnancies things can go wrong so quickly that mother and/or child will be dead before they can get to a hospital.

This summary of a similar study puts it well: "It is a perfectly reasonable choice but women need to be aware of the risks. They are mixing the very best with almost the worst. Women who choose a hospital birth are in effect hedging their bets – it may be not as nice an experience but it is safer when things go wrong." From: http://www.independent.co.uk/life-style/health-and-families/health-news/the-big-question-what-are-the-risks-of-home-births-and-are-they-greater-than-in-hospital-803504.html

When it comes to my life and my babies life, I'll hedge my bets, thank you very much.

tarynrom said...

I just wanted to say thanks for this post - I have been looking for something like this for a very long time. I am always confronted by my peers with this "problem" of life expectancy in regards to Paleo.

Reading through the comments has been even more informative and I just wanted to throw a big thank you out to all of you.

Excellent post.

abna4i22 said...

Short answer: no.
Median life expectancy in these groups is 45-50.

Long answer:
There are numerous errors of logic here, but I'll choose just one.
You argue that first child at 20, birth spacing 3.5 years, and 4-5 children required to reach replacement indicates a lifespan of 60. This data gets us to 35, or 36 if you assume a year of breastfeeding. So now we have 4-5 children, with the eldest at hunting age. That sounds like a barely functional family unit without the mother, until you look at the sociology of these groups you mention. Subsistence-level groups hardly reproduce a nuclear family unit, with women often having children by many different fathers and those children being raised and fed largely without reference to their parents. There's no reason to assume that every family needs one crone to preserve whatever wisdom age brings; one per group will be more than sufficient.

Second, a quick look at the actual data (V. Steffanson, Alaska, 1822-36):

Aleuts, Unalaska district
Died ages 1-4 -- 92
Died ages 4-7 -- 17
Died ages 7-15 -- 41
Died ages 15-25 -- 41
Died ages 25-45 -- 103
Died ages 45-55 -- 66
Died ages 55-60 -- 29
Died ages 60-65 -- 22
Died ages 65-70 -- 24
Died ages 70-75 -- 23
Died ages 75-80 -- 11
Died ages 80-90 -- 20
Died ages 90-100 -- 2


So, much better odds of dying by 55 than living past 70.

We're way better off today. Enjoy your bunless hamburger.

O Primitivo said...

Longevity Among Hunter- Gatherers: A Cross-Cultural Examination: http://www.anth.ucsb.edu/faculty/gurven/papers/GurvenKaplan2007pdr.pdf

O Primitivo said...

http://en.wikipedia.org/wiki/Life_expectancy
http://www.infoplease.com/ipa/A0005140.html

bcorbishley said...

Everyone knows...?
While your argument is pretty convincing, I would be more convinced if your research was more reliable. "Everyone knows" that Thomas Hobbes said life is "nasty, cold, brutish, and short." But that's not true. He said it was "solitary, poor, nasty, brutish, and short." (Mark Sisson got it right by the way.)

Don said...

Abna,

You just listed data that proves my point...among the Inuit, many people lived past 30 years of age. The highest mortality group in the data you gave was 25-45...the age group in which males are most likely to die due to injuries inccured while hunting. Your data shows 294 deaths among people aged 0-45, and 197 deaths among people aged 45-100. That suggests that 40% of this population lived past the age of 45 years, exactly my point.

Don said...

bcorbishley,

Are you faulting my presentation for not quoting Hobbes exactly? If you read carefully, I did not indicate that I was exactly quoting Hobbes, I called it a "Hobbesian claim" meaning a claim of those in the Hobbesian camp of thought. Otherwise, the arguments I made stand on their own, regardless of whether I quoted or paraphrased the Hobbesian claim.

bcorbishley said...

You're quibbling. Indeed protesting too much. I would be more inclined to believe the rest of your work if you said thanks for pointing this out and that you would strive to be more accurate in the future. I just happened to know this particular fact. How can I trust you to get other facts right?

Don said...

bcorbishley,

I'm quibbling?

Dr. Curmudgeon Gee said...

i never thought about that menopause would give survival an edge.

thanks.

pam (not an M.D.)

Ken D. Berry said...

Very nice article. I have no doubt that if the life expectancy of hunter-gatherers was controlled for accidents, infections controllable diseases, it would be better than ours currently. Folks shouldn't forget that hunter-gatherers lived in very dangerous and unprotected times, to blame their diet for their probable short life-span is silly.

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