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Help me grok this comment about diet, natural selection, and disease

Answered on September 12, 2014
Created June 25, 2012 at 6:12 AM

NPR has a blog article in which they highlighted comments about a previous post of theirs on the paleo diet.

One of the highlighted comments was this:

Robert McNealy (wooddragon) wrote: The term "Evolutionary Medicine" is a bit deceptive. Diet is not really influenced by natural selection, since most of the health ailments that show up due to a bad diet show up after breeding age.

Maybe it's late and I need to get some sleep but I'm having a hard time wrapping myself around this statement.

Can someone explain what it means and tell us if it's a valid criticism of paleo?

34b560c8b9ce660d7839fb7e29d7be89

on June 27, 2012
at 05:53 AM

But the fact that inferior diets have by and large replaced forager, horticulturalist and pastoralist groups is testament to the fact that diet can circumvent the process of natural selection--higher fertility and the organizational structure of civilization > HG lifestyle. If you can beat em outbreed em.

34b560c8b9ce660d7839fb7e29d7be89

on June 27, 2012
at 05:53 AM

Good points Todd B, I only brought it up because you stated that human children were unproductive members of society. However even in agricultural societies one of the basic assumptions is that higher fertility is not only possible due to more reliable food sources but necessary as larger families are needed to work the family farm. Longevity can impart some benefits obviously, especially in HG cultures where the elderly are more highly revered--without written language the knowlege passed along through oral traditions is more valuable.

Ae8946707ddebf0f0bfbcfc63276d823

(9402)

on June 26, 2012
at 02:01 PM

If anyone can comment on what I'm misunderstanding, I'd appreciate it. But to me, this is all good justification for a paleo-inspired diet. There was a time during our evolution when obtaining proper nutrients did affect survival - even at a young age. In more recent times, certainly since agriculture, food is more plentiful and obtaining proper nutrients largely only affects survival for older people (i.e., well after child birth). That's why we are no longer evolving (or doing so much more slowly) our ability to exploit new/different food sources.

Baa413654789b57f3579474ca7fa43d7

(2349)

on June 26, 2012
at 01:33 PM

...continued .... Woman B is still reproduces but because she dies earlier, Child B does not benefit from mom's knowledge and has a lower probability of survival. This also means that Woman B’s genes that predisposed her to dying earlier also have a lesser likelihood of being passed on to a third generation. This is obviously greatly simplified, as longevity is more complicated than a simple genetic disposition, but I believe that is generally the basis for the hypothesis.

Baa413654789b57f3579474ca7fa43d7

(2349)

on June 26, 2012
at 01:31 PM

Scotts, the way I think about it is this. Woman A is genetically predisposed to live longer (and in this hypothetical, does in fact live longer) than Woman B. Woman A not only passes on her genetic predisposition for a “long life” to Child A, she can also (due to that longer life) care for her child longer and pass on more knowledge. This inheritance of genetics and knowledge provides a greater opportunity for Child A to survive.

Baa413654789b57f3579474ca7fa43d7

(2349)

on June 26, 2012
at 01:20 PM

Amerindian, good article. I agree that modern culture has certainly skewed what we expect from children. However, there is a difference between contributing and being self sufficient. A quote from the article, "As a consequence, by the time they reach puberty Matsigenka kids have mastered most of the skills necessary for survival." So, it still takes more than a decade of care and instruction from elders, and even then the child has only mastered "most" of the skills needed.

34b560c8b9ce660d7839fb7e29d7be89

on June 26, 2012
at 02:04 AM

Biocultural evolution is the interaction between biology and culture, they coevolve alongside each other. Fire for cooking, stone tools for cutting are cultural adaptations that eliminate the need for powerful jaws and claws. Children not contibuting to resource accumulation is a product of our modern culture. http://m.newyorker.com/arts/critics/books/2012/07/02/120702crbo_books_kolbert?fb_ref=social_fblike&fb_source=home_multiline

7f8bc7ce5c34aae50408d31812c839b0

(2698)

on June 25, 2012
at 10:38 PM

Interesting. Would the benefit of tribal knowledge passed on from elders to young adults yield a evolutionary advantage/selection pressue, or merely a societal motivation to eat better and have better medicine? Have to think about that one for a bit.

211d4075d68b24cd0aa7ebfa94262bb9

on June 25, 2012
at 07:13 PM

If diet isn't influenced by natural selection, how does he explain why different species consume different foods even when they have the same foods available to them?

35b2cb4d450e5288895c255dfdfff35d

(5828)

on June 25, 2012
at 01:40 PM

Looking forward to the other studies. Thanks!

35b2cb4d450e5288895c255dfdfff35d

(5828)

on June 25, 2012
at 01:39 PM

Nice response!!

34b560c8b9ce660d7839fb7e29d7be89

on June 25, 2012
at 07:47 AM

He is saying that even an awful diet can get you to reproductive age and whatever happens after you've passed on your genes has no bearing on one's evolutionary fitness. It isn't entirely without merit, natural selection doesn't necessarily mean optimal, especially if "good enough" increases your reproductive value relative to others.

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7 Answers

5
Baa413654789b57f3579474ca7fa43d7

(2349)

on June 25, 2012
at 01:35 PM

The idea that natural selection only plays a point up to age of reproduction makes sense when it comes to animals that spawn a bunch of offspring and then have served their purpose in life (i.e., propagation of the species). However, humans are a much more complicated species.

Mark's Daily Apple has a relevant post: http://www.marksdailyapple.com/hunter-gatherer-lifespan/#axzz1yoN5YsQS

As Mark notes, "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."

35b2cb4d450e5288895c255dfdfff35d

(5828)

on June 25, 2012
at 01:39 PM

Nice response!!

7f8bc7ce5c34aae50408d31812c839b0

(2698)

on June 25, 2012
at 10:38 PM

Interesting. Would the benefit of tribal knowledge passed on from elders to young adults yield a evolutionary advantage/selection pressue, or merely a societal motivation to eat better and have better medicine? Have to think about that one for a bit.

Baa413654789b57f3579474ca7fa43d7

(2349)

on June 26, 2012
at 01:33 PM

...continued .... Woman B is still reproduces but because she dies earlier, Child B does not benefit from mom's knowledge and has a lower probability of survival. This also means that Woman B’s genes that predisposed her to dying earlier also have a lesser likelihood of being passed on to a third generation. This is obviously greatly simplified, as longevity is more complicated than a simple genetic disposition, but I believe that is generally the basis for the hypothesis.

Baa413654789b57f3579474ca7fa43d7

(2349)

on June 26, 2012
at 01:20 PM

Amerindian, good article. I agree that modern culture has certainly skewed what we expect from children. However, there is a difference between contributing and being self sufficient. A quote from the article, "As a consequence, by the time they reach puberty Matsigenka kids have mastered most of the skills necessary for survival." So, it still takes more than a decade of care and instruction from elders, and even then the child has only mastered "most" of the skills needed.

Baa413654789b57f3579474ca7fa43d7

(2349)

on June 26, 2012
at 01:31 PM

Scotts, the way I think about it is this. Woman A is genetically predisposed to live longer (and in this hypothetical, does in fact live longer) than Woman B. Woman A not only passes on her genetic predisposition for a “long life” to Child A, she can also (due to that longer life) care for her child longer and pass on more knowledge. This inheritance of genetics and knowledge provides a greater opportunity for Child A to survive.

34b560c8b9ce660d7839fb7e29d7be89

on June 26, 2012
at 02:04 AM

Biocultural evolution is the interaction between biology and culture, they coevolve alongside each other. Fire for cooking, stone tools for cutting are cultural adaptations that eliminate the need for powerful jaws and claws. Children not contibuting to resource accumulation is a product of our modern culture. http://m.newyorker.com/arts/critics/books/2012/07/02/120702crbo_books_kolbert?fb_ref=social_fblike&fb_source=home_multiline

34b560c8b9ce660d7839fb7e29d7be89

on June 27, 2012
at 05:53 AM

But the fact that inferior diets have by and large replaced forager, horticulturalist and pastoralist groups is testament to the fact that diet can circumvent the process of natural selection--higher fertility and the organizational structure of civilization > HG lifestyle. If you can beat em outbreed em.

34b560c8b9ce660d7839fb7e29d7be89

on June 27, 2012
at 05:53 AM

Good points Todd B, I only brought it up because you stated that human children were unproductive members of society. However even in agricultural societies one of the basic assumptions is that higher fertility is not only possible due to more reliable food sources but necessary as larger families are needed to work the family farm. Longevity can impart some benefits obviously, especially in HG cultures where the elderly are more highly revered--without written language the knowlege passed along through oral traditions is more valuable.

2
6da7ce6a4a250c46a6e78b5b4e22da83

(987)

on June 25, 2012
at 02:09 PM

Maybe I'm mistaken, but can't that quote be used to support the paleo diet? Some people want to critique the paleo diet by claiming that there has been enough time for humans to evolve to thrive on grains. But evolution operates through both time and selective pressure. Because humans can survive on grains until reproductive age (and then suffer the health consequences later), there is very little selective pressure, making it less likely that humans have evolved to thrive on grains.

I'm no scientist, but I seem to remember Matt Lalonde explaining this on Cris Kressor's podcast.

2
61844af1187e745e09bb394cbd28cf23

(11048)

on June 25, 2012
at 12:39 PM

This study, albeit small, suggests otherwise: http://www.newscientist.com/article/dn2994

Since Mom's diet affects the fetus and the quality of breast milk, it would seem that diet would create a larger impact than the statement you quoted implies. I would also surmise that Dad's diet would affect sperm quality and motility, thus impacting what is passed on to his offspring. I'll check for other studies when I get a chance this afternoon.

35b2cb4d450e5288895c255dfdfff35d

(5828)

on June 25, 2012
at 01:40 PM

Looking forward to the other studies. Thanks!

0
6120c989fd5b69f42a0834b69b87955b

(24553)

on July 10, 2012
at 11:34 PM

My N=1 pretty much proved to me that this isn't true. I managed to render myself infertile by my mid 20's via diet, but with the removal of grain, and addition of red meat and upping the saturated fat in my early 30's, seem to have brought it back.

0
Ae8946707ddebf0f0bfbcfc63276d823

(9402)

on June 25, 2012
at 01:48 PM

I will risk exposing my own ignorance with this response, but I've never really understood this argument to begin with. In times when food was not plentiful, it seems to me that the ability to exploit a new food source would help one survive/thrive better than others even up to child bearing age. Also, it seems better nutrition would increase fertility, reduce miscarriage, reduce infant mortality, etc. Sure, today, health problems related to diet may not affect these things, but I can't imagine the same was true for hunter gatherers during our evolution. What am I missing?

Ae8946707ddebf0f0bfbcfc63276d823

(9402)

on June 26, 2012
at 02:01 PM

If anyone can comment on what I'm misunderstanding, I'd appreciate it. But to me, this is all good justification for a paleo-inspired diet. There was a time during our evolution when obtaining proper nutrients did affect survival - even at a young age. In more recent times, certainly since agriculture, food is more plentiful and obtaining proper nutrients largely only affects survival for older people (i.e., well after child birth). That's why we are no longer evolving (or doing so much more slowly) our ability to exploit new/different food sources.

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on April 09, 2013
at 11:05 AM

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on July 10, 2012
at 08:50 PM

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