I was willing to concede you probably would know more about bears given I am in the wrong hemisphere to be familiar, but a little superficial digging showed you were quite wrong here. Grizzlies and polar bears most definitely do interbreed, though I can’t find a definitive source on their hybrid fertility levels. The species concept is a fuzzy and sometimes misleading one. Life does whatever it can get away with.
http://en.wikipedia.org/wiki/Grizzly–polar_bear_hybrid

My main point though was that small genetic changes (too small to cause reproductive isolation) between populations can nevertheless cause distinct differences in their phenotype and ability to fit into a niche. Polar bears and grizzlies can interbreed, but either pure species would not be viable in the other specie’s habitat. By extension small genetic differences in human populations may interfere with their capacity to adopt each other’s lifestyles in less than obvious ways. Scottish people do suffer sunburn in Australia, Africans suffer vitamin D deficiency in Sweden. Is it really racist to acknowledge such things? If so aren’t statements like “an asian and a european are closer genetically than an x african and a y african” also racist?

Current research as you describe has indicated that the gene sequence differences between human populations are not large. But the problem is that those studies miss a lot of the detail in population genetics on several levels. Firstly the data on a base genetic level is far from comprehensive- most of the current broad-scale population studies come from looking at variation in the sequence of the coding region of just a few genes. Entire genomes haven’t been sampled across human populations yet, and probably won’t be for a decade at least.
Secondly we have only just started to appreciate that there is a wide variation in gene copy number within populations. In humans this was recently discovered in a very salient example- gene copy number and expression levels of salivary amylase.
http://www.nature.com/nature/journal/v449/n7159/full/449155a.html
In short the number of copies of the gene for salivary amylase (useful in digestion of starch) was found to correlate with the amount of amylase produced, and more interestingly to vary many-fold between different humans, with humans from low starch HG groups having lower gene copy number than HG and ag humans with a high starch diet. The really interesting thing for me was that the distribution in copy number variations in each population indicated that the variation in the trait shifted rapidly and repeatedly throughout human history in response to diet.

Thirdly on human genetic evolution is the issue of non-coding DNA and RNA. Only a small fraction of our genome is read into proteins and enzymes like amylase. The rest of it forms a tangled network of gene products that control gene expression levels that we have only recently started to study. In short we have no real idea what this system does, how varied it is between people and how it might evolve.

Fourthly we know that gene activity is influenced in response to the environment (phenotypic plasticity) but that these changes have effects on the gene activity of subsequent generations (epigenetic change). Morphology, metabolism (ie diet) and immunity seem to be the areas most influenced by this phenomenon. So although your DNA sequence may be identical to an authentic HGer, if your mother ate big macs and potato chips and their mother ate acorns and clams then your individual appearance and responses to your diets and environments could be very different. This is even seen in identical twins where often they look anything but identical.
This brings up an analogy I have been thinking of for a while. Research shows that Japanese people have less knee problems than westerners because of their habit of sitting in a kneeling position on the floor. So you might think that adopting a kneeling position would improve the condition of your knees. Except the behavior changes the growth of the knee during childhood. An unfit westerner adopting the Japanese habit later in life is likely to do more harm than good. The critical window for changing their development has been passed. A similar process is believed to be behind the narrowing of jaws in response to an excessively soft processed diet. Many aspects of our development are guided by our environment and our behavior, so rapidly changing either later in life can have unpredictable effects.
I agree that parts of the Americas probably had population density comparable to Europe at the time that smallpox and other epidemics wiped them out, but what about Australian Aborigines? Not only the relatively populous coastal regions were decimated, but the very sparsely populated central deserts as well. Early explorers often documented horrific smallpox scarring on survivors and tales of high casuality rates coming decades before the first white explorers entered the region. Isolation did not protect these people from epidemics forever. The lesson seems to be that any disease on the same continent will come to you soon enough.
You are correct that a critical factor is immune system naivety to the virulence new pathogen. But this places peripheral HGers at a distinct disadvantage. As is commonly known children are often able to pass through an infectious illness with fewer effects than naïve adults. HG groups living on the same continent as remnant agriculturalists will probably suffer periodic exposure to epidemics, shifting the burden of the disease from relatively resilient children to more vulnerable adults. Add in the relatively low reproductive rates and restricted genetic diversity of small tribes and you have a potential problem with long-term group viability. Diversity is the key, and smaller populations are on average and over time less diverse than large ones (though the recent mix up of humans moving all over the globe does help a little).
Even though ag humans have some improved resistance to many epidemic pathogens these are still serious infections in those who have not yet fought them off (or been vaccinated). And here we come to the obvious problem that smallpox has been eradicated for half a century and is no-longer commonly vaccinated against- that is a terrifying situation of “virgin soil” for virulence to burn through.

On my suggestion that HG groups are hardwired to respond differently to diet you only have to look at the record with respect to myopia, that we now know is related to high blood glucose levels during development.
“While fewer than one per cent of the Inuit and Pacific islanders had myopia early in the last century, these rates have since skyrocketed to as high as 50 per cent.”
http://www.karlloren.com/Diabetes/p49.htm

Different individuals, and by extension different population groups (“races” if you must”), have differing responses to diet, sometimes small, sometimes significant. The data suggests that HGer populations recently introduced to western diets have a more damaging response than western populations, though differing socioeconomic status are undoubtedly part of the overall health status as well. Is that really such a racist and offensive idea? It seems inescapable to me that the reverse is also true- individual westerners will each respond differently to adopting a HG diet, and the full effects will be played out across more than one generation.
I think we can agree that rich and poor are inadequate terms to describe differing diets. If anything a western diet is energy rich and nutrient poor, a HG diet is energy poor but nutrient rich, by comparison.

On barely processing corn- I think you need to stop arguing at the dinner table and chew your food more carefully. Unchewed corn kernels have a waxy coating that protects them from digestive enzymes. And the process of digestion and elimination takes around 24 hours or more.
True wheat allergy is actually not the most common: http://www.foodallergy.org/allergens/index.html
“Although an individual could be allergic to any food, such as fruits, vegetables, and meats, there are eight foods that account for 90% of all food-allergic reactions. These are: milk, egg, peanut, tree nut (walnut, cashew, etc.), fish, shellfish, soy, and wheat.”

Quite a mix of “paleo” and “neo” ingredients there. Depending on source and demographic of sufferers the most common food allergy is reputed to be peanut (neo- in children), egg (paleo?- in children) or shellfish (paleo- in adults). Food intolerances are more complex, but wheat sure is hard to digest for many people if it isn’t fermented (as is most industrial wheat today). I just started doing fermented oat and buckwheat porridges for breakfast- it seemed very tasty and no deleterious effects so far. The B-vitamin boost to energy levels is tangible too. Pure unfermented oat porridge sometimes had a sour taste for me (rancid fats from milling in some batches).
History is littered with accounts of ag-civ individuals becoming incorporated with HGer tribes, and many of them found it to their liking (but far from all of them http://en.wikipedia.org/wiki/Eliza_Fraser). What is lacking is a detailed historic example of a small group of ag-civs successfully setting out to become a new HG tribe together. HGers have reappeared in regions where civilizations have collapsed, but direct descendency between the two populations has never been proven as far as I am aware, leaving the possibility the ag-civs died out and different HGers returned. The same problem exists for changes in height and health with the reverse process of the introduction of agriculture to HGers- can we be certain that the short sickly farmers are actual descendants the tall healthy HGers? So oral history aside, is there any solid genetic evidence of rewilding en masse and from scratch? If genuine HGers are essential to the success of the group in the rewilding process, do you have any mechanism to recruit them into your tribe? What would newbie HGers offer to authentic ones? Are there even any genuine HGers left in North America anyway?
Sabine Kuegler’s story had some interesting detail. The tribe they stayed with “was being decimated by inter-tribal warfare, revenge killings and disease….Doris Kuegler, a nurse, became unofficial midwife to the community, whose women were dying unnecessarily in childbirth. She saved the life of a lame boy called Ohri, who became like a brother to Sabine. When Ohri eventually died of TB. ….. Her mother wanted her to return to Indonesia but she felt too ashamed: to be pregnant but without a man was a serious breach of the tribe’s social code. In the Fayu world there is no such thing as an illegitimate child because sex outside marriage is punishable by death.”.
There is just too much there to start picking at- it speaks for itself. The long term health impacts of her experience were not evident because she was only there ten years, her resistance to local diseases like malaria was likely untested given her parents were medics, she did not reproduce, and apart from all that if she had reproduced it may have been with a genuine HGer, inferring local genetic adaptation to her children. This example lends zero support to your idea that a band of pure ag-civs can independently transform themselves into a new HG tribe and achieve long-term viability.
Void-We are the first polysymbiotic species on this planet.
Jason-Can you name any species that isn’t polysymbiotic? I don’t know of a single one.

Void> There is no narrow definition of symbiosis, so this is a wobbly point to argue around. The narrowest symbiosis (eg endosymbiosis) probably tops out at insects having up to ten microbes living within their tissues, on top of ubiquitous mitochondria etc. Counting the digestive tract and epidermal symbionts is not enlightening as all multicellular organisms have a complex community. Multicellular to multicellular symbiosis usually excludes predator/prey/parasite relationships in food webs and focuses on mutualism, but the borders between them are fuzzy. Taking a classical definition of mutualism humans are indeed exceptional for their ability to develop multiple mutalistic relationships. A typical early agricultural community would carry a few dozen crops and maybe half a dozen animals, and a dozen or so distinct polybiotic cultures for fermentation. Modern ones are a synthesis of the original regional ag biomes and can contain 2-3 times more diversity overall. Add in the weeds, pests and parasites and you are moving away from narrow mutualism but it is a significant part of the diversity of the ag biome. Can you name a species with much more than ten ectosymbiotic mutualistic partners, even allowing for microbes?
For example- A tree may have (being generous with redundancies) :
1. Mycorhyza (universal)
2. Nitrogen fixing agrobacteria (or equivalent) (common but not universal)
3. Pollinator A (common but not universal)
4. Pollinator B (common but not universal)
5. Pollinator C (common but not universal)
6. Fruit disperser A (common but not universal)
7. Fruit disperser B (common but not universal)
8. Ant guard (reward via extrafloral nectaries) (rare)

Secondly to Dana

I apologise, as I have before, if my presence here is unwelcome. Jason is well within his authority to banish me from the site if he wishes to moderate the discussions. But I think it is useful for both sides to examine their assumptions and analysis. The world is most definitely headed toward a major crisis, and radical lifestyle changes are coming. Our planned responses could have life or death consequences. Is it really so tiresome to periodically shake down our ideas and see how sturdy they are?

Dana- 1. There were no HGs living in their immediate vicinity, and
2. They hadn’t developed anthropology yet.
Void>On point one I can only highlight that very few agcivs today have authentic HGers in their immediate vicinity (are there any at all in North America? In Australia the tribes maintain some contact with the old ways but more traditions are lost every year). Those few authentic HG tribes left seem to have a distinct animosity toward agcivs (eg Andaman Islanders) and are unlikely to have any incentive to care for and reeducate us. Does the tribe of anthropik have strong links to your remnant indigenous community?
On point 2 I would suggest that there is only so much that anthropology can currently contribute to successfully adopting a genuine HG lifestyle. For a start the documented information is woefully incomplete- for instance much of the ethnopharmacology of tribes was lost before it could be recorded, and that which was written down is often vague and incomplete. Secondly even if we had a detailed knowledge of how historic HGers lived, we have to be able to apply that to a radically changed environment (through environmental damage and now ongoing climate change). Beyond that putting theory into practice is a far from straight-forward process. Would you kill a venomous snake based on a paragraph of advice? Collect wild honey? Identify and eat an unfamiliar plant? (ala Alex Supertramp).
Dana- So we now have this wonderful chance for a significant number of us to survive our own collapse, despite all the damage we’ve done and all the cultures we’ve destroyed.

Void> Fair enough if there is a distinct, fast collapse. But how will you recognize it when it comes? What is a meaningful trigger for getting the tribe of anthropik out of their suburbs and into the woods together? Have you agreed on what it would be? Or will it be too late to get out or even discuss it by the time an obvious trigger comes? What if there is a slow and drawn out collapse instead over decades?

Perhaps I should remember what they did to Socrates for asking too many stupid questions……

Secondly, I don’t have a lot of time to go through lots and lots of verbose comments so I apologize if this has already been said. But there are two very obvious reasons why the ancient Middle Eastern cultures that collapsed from agriculture didn’t revert to HG lifestyles.

1. There were no HGs living in their immediate vicinity, and

2. They hadn’t developed anthropology yet.

Do I really need to say this? Do I really need to spell it out? If civilization and industrial technology are really vital to human existence then why are the anti-HGs here not USING IT to answer their own damn stupid questions?

We know these things because if there had been HGs living near the agricultural settlements that collapsed, they would have taken in the survivors and taught them how to live differently, assuming the two groups could learn to get along.

We also know these things because wherever an agricultural civilization has NOT yet wiped out the local HGs, individuals in the agciv who were not benefiting from it abandoned it in favor of living with HGs.

But with agcivs that did not border on HG societies in any way, they either wouldn’t know HGs existed, would be superstitiously afraid of HGs, or would believe HG lifestyles inferior for some reason, so they wouldn’t seek them out.

We had these same issues, and still do to some extent. There’s also the point that just because we have science doesn’t mean we will use it wisely and well–we have biases and sometimes (often) we filter information through those biases, and so completely misinterpret what we’re seeing, particularly with animal (including human) behavior. But where we use science WELL, and can therefore properly understand what we’re seeing, we have the capability of understanding other cultures in a way that’s never been done before where the two cultures in question did not neighbor one another.

So we now have this wonderful chance for a significant number of us to survive our own collapse, despite all the damage we’ve done and all the cultures we’ve destroyed. So it really doesn’t matter what, say, ancient Iraq did when their topsoil washed away. We’re not ancient Iraq, we’re not ancient Egypt, we’re not ancient anything else. We’re us, we operate under materially different circumstances, we have understandings about the world that haven’t existed in any other time or place, and we can do things differently as a result.

Mmkay? All righty then.

And a polar bear can breed with a grizzly, but I wouldnt be too hopeful that a grizzly would survive well enough to reproduce on an ice flow. “Subspecies” for want of a more elegant term, are capable of remaining cross fertile while adapting to distinct niches.

Thank you for quite neatly illustrating my point. Yes, subspecies are distinct groups on their way towards speciation; they can produce viable offspring, though importantly, their offspring “breed true.” But your comparison is telling. Polar bears (Ursus maritimus) most likely speciated from the Kodiak bear (Ursus arctos middendorffi), generally considered a subspecies of brown bear. The grizzly bear (Ursus arctos horribilis) is a different subspecies of brown bear. While grizzlies and Kodiaks can interbreed, grizzlies and polar bears—your example—cannot. They are two different species.

But in humans, we can’t even draw lines of subspecies, at least at present. There may be different subspecies of Homo sapiens in the archaeological record, but none of them survive today. Native Americans, African Bushmen and Australian Aborigines are not distinct species of humans, nor are they even distinct subspecies. We are all Homo sapiens sapiens. We produce offspring with one another with no difficulty; we don’t even breed true. The vast majority of the genetic diversity in our species is well known to be contained inside of Africa, precisely as one would expect if Homo sapiens evolved in Africa, and all non-African specimens descended from a relatively small population that left the original continent. The genetic differences between you or I compared to a Native American or an Australian Aborigine shrink to nothing compared to the genetic diversity that separates a M’buti Pygmy from a !Kung Bushman.

In other words, I’m afraid the facts make pure balderdash out of your speculations. And frankly, besides being rather baseless, it’s also quite alarming in its reminiscent overtones from the bad old days of Ota Benga.

The real question is how deeply adapted agricultural humans are to the agricultural niche. We seem to differ just on where we estimate the depth of the symbiosis to lie. I am mostly agnostic- I think we lack the data needed to make any solid conclusions at present.

We know for certain that the agricultural lifestyle still makes us sick, and that we’re still healthiest when and to what degree we are able to emulate the hunter-gatherer lifestyle, whether in diet, routine, or nearly any other aspect. I think the data is incredibly consistent and quite solidly points to the rather obvious conclusion that 10,000 years is hardly enough time to even seriously begin the process of turning a chimpanzee into an ant.

Diseases like small pox raced through new world peoples and the natives in Australia despite them living at very low average densities.

They didn’t have very low average densities; read Charles Mann’s 1491. The Americas were actually rather thickly populated, perhaps even more thickly populated than Europe at the same time. But there’s also virulence, or what epidemiologists refer to as “virgin soil.” The European diseases had been in an escalation with European immunities because of their run-away population densities (the American population had grown more steadily, thanks to horticulture, without the constant ravages of plague found in Europe). So the diseases were incredibly virulent, and the American population had no immunity to them whatsoever. Even if they had originally been as depopulated as Europeans recorded after traveling through the post-apocalyptic aftermath of the diseases, the sheer virulence compared to their immunity may have been able to overcome that.

Today, that’s no longer a concern. There’s nowhere on earth where the ravages of centuries of plague haven’t taken their toll and left us with immunities. There’s no more “virgin soil,” and so nothing with that kind of virulence left. Even the most terrible plagues of the modern world are absolutely tame when compared to the impact of smallpox on native America.

Small tribes still need to maintain regular social and trading contact with the wider community, and many diseases (unlike ebola) can remain infectious for long periods of time.

Diseases that take a long time to incubate are typically not nearly as virulent.

It appears that higher levels of population intensity are needed to create a new pathogen but they are not necessarily required to sustain their spread.

Mainstream epidemiology disagrees heartily. This is very basic, introductory material in that field: without a sufficient population density, diseases have a harder time spreading, and if they fail to spread, that can often mean their extinction.

I stand by my original point that there may be significant medium term epidemiological hazards in reverting to small reproductive human groups.

In that the bubonic plague will not disappear just because the civilization that spawned it collapsed, yes, you’re absolutely right. However, any hunter-gatherer or even horticultural society will enjoy advantages in stopping the spread of epidemic diseases that we do not have. So in the medium term, yes, you will not have the plague-free paradise of our ancient ancestors. It will take time for epidemic diseases to go entirely extinct. But they will be going extinct. Things will be getting better from the very moment you begin hunting and gathering. But if you’re expecting a magic switch to immediately wipe out all epidemic disease, no, that’s not going to happen. Still, I would say that beginning the process of extincting all epidemic disease is certainly an improvement over the current state of creating new epidemic diseases.

Also the black death in Europe killed about a third to half of the people, but it kept reappearing in waves for well over a hundred years.

Yes, and there were incidents of bubonic plague before that, as well. The Justinian Plague was even more virulent than the Black Death, and would have been remembered as the most important historical event of its era had it not been overshadowed by the collapse of Rome at the same time. Each time, the survivors left a population with more immunity, so each successive wave was smaller, with smaller and smaller populations of people vulnerable to infection in the first place.

It didnt burn out sufficient density of overall people to support it in one wave.

You’re misunderstanding the statement. The Black Death ended when it reached the point where everyone left alive was either immune, or had run off into the hills. It ended essentially because Europeans lived like hunter-gatherers for a season or two. That left no one to infect, so it died out. Yes, later waves came through later, after the population had rebounded, population densities had gone back up, and those immune individuals had had more children, only some of whom inherited that immunity. The next wave came precisely once the factors that had ended the Black Death ceased to exist. But that simply illustrates my point, one you’ll find in any introductory epidemiology textbook: population density is a cause of epidemic disease.

Depending on the nature of the disease and host a larger, more genetically diverse population can be much more resistant to a plague than a smaller spread out one.

The key there is diversity, not density. Population density increases the incidence of disease. Population diversity increases the odds that an immunity exists and can be propogated. Hunter-gatherer populations are far more diverse than civilized populations, genetically; the two are not necessarily correlated. Civilizations have large, dense, homogeneous populations, providing the perfect combination of everything pathogens need to kill huge numbers of people, and that’s why the history of civilization is filled with waves of pathogens killing huge numbers of people. Hunter-gatherers have small, dispersed, diverse populations, providing the perfect combination of everything that stops the spread of pathogens, and that’s why we cannot find any evidence of any epidemic disease prior to the Agricultural Revolution. You can’t even blame it on lack of evidence; we do extensive archaeological studies of plague victims, so why can’t we find archaeological evidence of earlier epidemics, unless they simply didn’t happen?

Now, you might argue that Pandora’s Box is already opened, and to some extent, that’s true. Living as hunter-gatherers won’t make those epidemics die out overnight. But it will begin to make them die out. Every day that we live as hunter-gatherers, every epidemic disease will grow smaller and weaker, until they go extinct entirely. Hunter-gatherer life won’t make every legacy of civilization blink out overnight; sometimes, it just begins the process of healing that problem, as in this case. Living as a hunter-gatherer won’t ensure perfect health immediately; it will just begin to immediately improve your health vastly.

Seeing how recent hunter gatherer peoples often suffer greater health problems on an agricultural diet than those with an agricultural heritage makes me suspect that the reverse may be equally true.

I am, frankly, a little disgusted by this statement, in the same sense that the story of Ota Benga, referenced above, disgusts me. Displaced hunter-gatherers often suffer greater health problems, yes, but it hardly has much to do with biology. Hunter-gatherers are subsumed into our civilization as the poorest of the poor. Their health problems are the same problems of malnutrition (including affluent malnutrition; malnutrition is not only lack of nutrition, I am using the word precisely here) suffered by the poor throughout civilization. To suggest that the toll of social injustice should be ascribed to genetics or biology is truly nothing less than disgusting. Take a look at the modern U.S. Indian reservation. Are you honestly going to tell me that the health problems suffered by Indians today have more to do with their biological differences, than the ongoing genocide we have placed them in?

Our agriculturalist biology may be finely tuned to take in richer resources and direct them to intensified reproduction and immunity.

That is simply impossible—if anything, it would have to be adapted to take in far poorer resources. Foragers eat a widely varied diet of meat, nuts, berries, tubers, and greens, all of them far more nutritionally-dense than anything even the richest Westerner today enjoys. For instance, once cup of dandelion leaves will provide you with more vitamin C than a whole carton of orange juice, while wild meat avoids nearly all of the health risks discovered in recent decades in corn-fed beef from cows who’ve spent their entire lives in CAFO’s.

But the fact of the matter is, no fine tuning has occurred in our ability to process these foods. We know this for a fact. We barely process corn, for instance; you can see the evidence of this for yourself in your toilet bowl just a few hours after you eat any corn-on-the-cob. Wheat allergy is by far the most common food allergy, and even for those of us who aren’t immediately allergic to wheat, it still causes long-term problems, like cancer. Milk also kills us slowly, even when we are “lactose tolerant.” We are not finely-tuned to these foods; we’re really not tuned to them at all. 10,000 years of accelerated evolution has accomplished an incredible feat: we can just barely swallow these foods, and they won’t immediately kill us. They’ll just kill us slowly, over time. Given the nature of these foods, that is a remarkable evolutionary feat, but to mistake that for “finely tuned adaptation,” or even adequate adaptation at all, is simply absurd.

The faster we try to rewild, and the smaller population we do it with, then the higher the mortality and loss of reproductive fitness in those going through the process. Behavioural adaptation (retraining) can help, but there are limits to everything.

There’s simply no evidence for this. There is no turning around to worry about. We never got far enough along the road to full domestication to turn around from. Yes, we’ve probably lost up to 10% of our cognitive capacity permanently, but for the most part, we’re physiologically identical to modern hunter-gatherers. Rewilding is, save for some minor details, an entirely behavioral process.

History is littered with accounts of individuals and whole populations rewilding at every opportunity, and never have they suffered the setbacks you speculate about. People have “gone native” or “gone to Croatan” whenever possible, but they’ve never suffered from these problems that you have baselessly imagined. In Letters from an American Farmer, J. Hector St. John de Crevecoeur wrote of the steady loss of Europeans rewilding, noting, “thousands of Europeans are Indians, and we have no examples of even one of those Aborigines having from choice become Europeans!” Benjamin Franklin noted, “No European who has tasted Savage Life can afterwards bear to live in our societies.” Even today, there are those who “go native” with great ease when presented with the opportunity. Take, for instance, the case of Sabine Kuegler; she lived a wild life from the ages of 7 to 17, though clearly of the exact same genetic stock as you or I. Where were the long-term health impacts for her, or for any of the thousands of domesticated, civilized individuals who have successfully rewilded throughout history without showing any sign of any of these complications that this vaguely racist speculation, with its disturbing echoes of social Darwinism, would predict?

Science is a fairly simple process: the proof of an hypothesis lies in its ability to make accurate predictions. Yours makes predictions, yes, but none of them are true. What does that say about the hypothesis? It’s not a particularly new thought; it was very popular at the turn of the last century, and was one of the founding ideological pillars for movements like the Nazi party in Germany. It’s simply been widely discredited and tossed aside as completely baseless, and utterly without evidence or merit. So for your own intellect as a person, I suppose it is a compliment that you’ve independently retraced the steps of Häckel and other geniuses, but as far as researching the claim and its implications, the first half of the 20th century already largely saw to that work, so we can skip that, reject this whole notion, and move on.

To start with people tend to obtain access to a new food source through careful processing (e.g. fermenting cow milk, which makes it edible to those without lactase, or soaked and roasted acorns to cope with tannin content).

In this particular case, your attention to detail isn’t revealing, but obfuscating. Fermentation, as in yogurt, breaks down the lactose. Lactose-intolerent people can eat yogurt to their heart’s content. The gap from that to drinking cow’s milk is as simple as some people not throwing up. It’s a simple matter of a well-known mutation on chromosome 2.

Human ability to adapt behaviourally to use many other species allows us to adopt a strategic position to take advantage of positive evolutionary changes as they occur.

Exactly. Now, in light of that, how can you defend your previous speculations about the biological barriers to rewilding?

We are the first polysymbiotic species on this planet.

Can you name any species that isn’t polysymbiotic? I don’t know of a single one.

And a polar bear can breed with a grizzly, but I wouldnt be too hopeful that a grizzly would survive well enough to reproduce on an ice flow. “Subspecies” for want of a more elegant term, are capable of remaining cross fertile while adapting to distinct niches. Reproductive isolation is a distinct issue from ecological adaptation. The real question is how deeply adapted agricultural humans are to the agricultural niche. We seem to differ just on where we estimate the depth of the symbiosis to lie. I am mostly agnostic- I think we lack the data needed to make any solid conclusions at present.

“Without large, dense populations, epidemic diseases die out. ”

This makes no sense to me. Diseases like small pox raced through new world peoples and the natives in Australia despite them living at very low average densities. Small tribes still need to maintain regular social and trading contact with the wider community, and many diseases (unlike ebola) can remain infectious for long periods of time. It appears that higher levels of population intensity are needed to create a new pathogen but they are not necessarily required to sustain their spread. I stand by my original point that there may be significant medium term epidemiological hazards in reverting to small reproductive human groups. These effects are also important for the resistance of a species to mundane pathogens and parasites (most of which we know little or nothing about), not just epidemic ones.

Also the black death in Europe killed about a third to half of the people, but it kept reappearing in waves for well over a hundred years. It didnt burn out sufficient density of overall people to support it in one wave. Depending on the nature of the disease and host a larger, more genetically diverse population can be much more resistant to a plague than a smaller spread out one. There isnt a simple linear relationship between population density and the ultimate impact of diseases.

On our responses to diet, and the possibility that agriculturally derived humans are significantly different to hunter gatherers, I would draw on the analogy of many cultivated plants. These are often termed gross feeders and they differ from wild plants in their ability to respond to a higher level of nutrients and water but produce higher outputs in return. Put a wild plant in a gross-feeder’s environment and it may well become soft, bloated and susceptible to disease and insects, if it responds at all. Equally putting a gross-feeder into the wild will see it become stressed and stunted, losing its competitive edge.

Seeing how recent hunter gatherer peoples often suffer greater health problems on an agricultural diet than those with an agricultural heritage makes me suspect that the reverse may be equally true. Our agriculturalist biology may be finely tuned to take in richer resources and direct them to intensified reproduction and immunity. Pushing us too quickly in the other direction may see us lose our competitive edge. So the question isnt just “how far have we come” but also “how quickly can we turn around” regarding “re-wilding”. The faster we try to rewild, and the smaller population we do it with, then the higher the mortality and loss of reproductive fitness in those going through the process. Behavioural adaptation (retraining) can help, but there are limits to everything.

Your story of a mixed group of people drinking cow milk one day and only some not throwing up misses the nuances of how behavioural and genetic adaptation actually tend to happen. To start with people tend to obtain access to a new food source through careful processing (e.g. fermenting cow milk, which makes it edible to those without lactase, or soaked and roasted acorns to cope with tannin content). In a culture that is already consuming a significant amount of processed food then variations that allow tolerance of less processing become advantageous to individuals. Early reports of the Australian aboriginal diet suggested they had higher tolerance of local plant toxins than Europeans for example. A complementary thing happened with the potato. High alkaloid potato species were gathered then cultivated first but were subject to lengthy processing to make them edible (still the case in the Andes). In this case the plant came to the party by developing low alkaloid strains, enhancing the symbiosis with humans. People didnt nibble on poisonous wild and raw potatos for generations until a sweet one was found.

Human ability to adapt behaviourally to use many other species allows us to adopt a strategic position to take advantage of positive evolutionary changes as they occur. We are the first polysymbiotic species on this planet. This mobile ecology may in fact prove to be more resilient to climate change in the long run.

You do know by the way that I am also Shane S?

I didn’t; thanks for sending me that article. It’s really a much better one than the one you’re linking to here: its data is more recent, and much more reliable.

So their results suggest we have undergone close to as much genetic change in the last 10, 000 years as we did in the entire history of our species.

And doesn’t that alone suggest your quick arithmetic above might be a bit off? After all, we’re still perfectly capable of breeding with the !Kung. Modern hunter-gatherers are not a different species by any stretch of the imagination. We are biologically nearly identical to modern hunter-gatherers. What differences have appeared—lactose-tolerance, larger numbers of antibodies, etc.—are, in the grand scheme of things, trivial.

Do you have a different way of interpreting the papers result?

Largely, no, but we seem to have come to vastly different ideas about the implications of those interpretations, nonetheless. The process of adapting humans to civilization began as soon as civilization began, and naturally such a drastic change would see a period of increased evolutionary activity: it leaves a lot of low-hanging fruit around. People who could drink cow’s milk without throwing up, for instance, would immediately have distinct advantages over their chronically starving peasant neighbors. But ultimately, a truly civilization-adapted human would look more like an ant or a bee, perhaps, and trying to reach something like that from the starting point of, essentially, a chimpanzee, is an extremely long evolutionary road. Adapting to civilization means reversing nearly all the primary characteristics of primate existence evolved over the past 65 million years. Have we begun that transformation? Absolutely. We have become domesticated, there’s no doubt about that. But we still have far more in common with our Pleistocene ancestors than not. We are still primarily adapted to a hunter-gatherer way of life, far moreso than to any kind of agricultural lifestyle. As evidence, I point again to modern hunter-gatherers, as well as to our biological shortcomings to a civilized lifestyle, compared to, for instance, actual granivores like birds, or socially to actually hierarchical species like ants or bees. So, my interpretation of these results is the same as when I cited similar results as evidence in my own argument years ago: yes, we have begun to adapt to this way of life precisely as evolutionary theory would predict, but we have also only begun that process, and it will still be hundreds of thousands of years before we see anything that could reasonably be considered a human adapted to a civilized lifestyle. Until then, we will remain Pleistocene animals out of our element.

For example with tolerance of infectious disease there may be a difficult interim period where the diseases of dense populations persist but where the benefits of a broad and dynamic genepool are no longer present to counter-act them.

Epidemiologically, this makes little sense. Without large, dense populations, epidemic diseases die out. The Black Death ended in Europe mostly because it killed so many that no dense populations continued, which could continue the plague, for instance. Large populations allow for the spread of epidemic diseases, not for their cure; the only benefit provided by dense populations is that after the plague burns through the population, those who survive pass on their antibodies disproportionately. Most Europeans today have a much greater resistance to bubonic plague, because their ancestors were necessarily the ones who happened to survive the Black Death.

After the collapse of civilization, epidemic diseases will undoubtedly still exist. The question will be how will they spread. Hunter-gatherers will enjoy the best immunity that can be provided, even compared to modern, Western medicine: they’ll be isolated. Even if a particular hunter-gatherer band did become infected, it would only provide a very small population for the disease to rip through before it would die out, lacking any others to infect. The spread of ebola is an excellent example: originating in tribal Africa, it did decimate many villages and bands, but because of the lower population density compared to, say, pre-plague Europe, the disease has not yet been able to have the same kind of global impact.

Think of the rise of an epidemic like randomly striking matches. In a sparsely-populated world, you randomly strike a match, and throw it in a bucket of water. In a densely populated world, you randomly strike a match, and throw it in a bucket of kerosene. Protection from epidemic disease is really one of the best arguments for a hunter-gatherer lifestyle; in medieval Europe, it provided the sole motivation for many who found that, alone, motivation enough.

Reversion to a reproduced primitive diet may have shown some documented short term health benefits, but do we really know what all the long term effects across generations of previously agricultural humans will be? For example are agriculturally derived human females sufficiently fertile on a genuine HG style diet? Swings of a few percent either way with such critical traits can mean the difference between a population explosion or rapid extinction.

It could, but what would the mechanism for this be? We certainly know that on a hunter-gatherer diet, that women are not always fertile. Of course, the general problem is the over-fertility of agriculturally-raised women, so the lower fertility that a paleo diet induces is one of its biggest advantages. Again, the biological differences between us and modern hunter-gatherers is incredibly trivial. The modern-day Swiss milk maid may be able to ingest milk without immediately vomitting, but she still hasn’t adapted to take anything but the most superficial nutritional value from it, nor has she adapted defenses against its side effects. Her biochemistry may have changed in her lifetime to want more sugars, but we are talking about adaptations in a single lifetime, not appreciable genetic changes that would pass from one generation to the next. Even after 10,000 years of accelerated evolution, genetic adaptations to bioregion have had a much bigger impact than adaptations to civilized lifestyles.

I’m currently about to get back to work from so I can’t address everything immediately. I’ll mull over it and hopefully respond soon, if not after the annual plastic tree festival. You do know by the way that I am also Shane S? I send you tidbits like that as I find them as I think our current quality of data on the topic of human evolution and ag is still lacking in many areas.

I did want to focus more on the accelerated human evolution data. Their quantification found that we started undergoing evolutionary change at an accelerated level 40, 000 years ago, and reached a rate 30-40 times above that of our longer evolutionary past by 5000 years ago. So conservatively just looking at the last 5000 years we have undergone the equivalent of 5000 x 35 = 175 000 years at deeper paleolithic levels (~20% of our entire species history). If you add in the area under the triangle running back to 40, 000 years with an assumed linear rate of change there is another 35, 000 x 35 x 1/2 =612500 years, totalling 787 500 years equivalent evolution, or about as long as modern humans have been around.

So their results suggest we have undergone close to as much genetic change in the last 10, 000 years as we did in the entire history of our species. This seems like more than scratching the surface. The report only studied changes in genes. Changes in epigenetics are potentially an even more important element.

The rate of evolutionary change isnt just a function of time and selection pressure, but also of population size. By supporting much greater densities of human populations agriculture facilitated the evolutionary changes necessary to allow us to adapt.

Do you have a different way of interpreting the papers result?

Attempted reversion of human groups to the previous lifestyle could involve unanticipated downsides. For example with tolerance of infectious disease there may be a difficult interim period where the diseases of dense populations persist but where the benefits of a broad and dynamic genepool are no longer present to counter-act them. Reversion to a reproduced primitive diet may have shown some documented short term health benefits, but do we really know what all the long term effects across generations of previously agricultural humans will be? For example are agriculturally derived human females sufficiently fertile on a genuine HG style diet? Swings of a few percent either way with such critical traits can mean the difference between a population explosion or rapid extinction.

But we’ve discussed this previously, I believe in the Thirty Theses. Earlier studies suggesting the same conclusion were used to buttress my argument about what a radical shift we’ve undergone in lifestyle, which would predict an accelerated period of human evolution, since the more radical the shift in lifestyle, the more things there are that need adapting to. We need this kind of accelerated adaptation just to make it viable, but as I showed in that previous work, we’re still far, far from adapted. Take the case of lactose tolerance. As late as the Roman empire, medical texts were listing cow’s milk as a purgative. Yes, the lactose-toleration mutation from Sweden and the Middle East allows us to drink cow’s milk without immediately vomitting, but we’re still helpless against the long-term effects of drinking milk (see Thesis #20, I believe). Which is to say, yes, we have begun adapting to agriculture, as you’d expect, and being a mere 10k years into the process, we’ve begun to scratch the surface of that endeavor. If we can dedicate another 100,000 years or so, we might even produce a human who isn’t made chronically ill by civilized life. But the fact remains that we are still essentially Pleistocene animals, struggling to adapt to a radically anti-human way of life.

Really, the findings aren’t stunning at all if you expect humans to behave like any other animal—which is precisely why so many people find this so stunning. According to the technophilic fantasy, technology removed us from evolution. But that’s precisely why I’ve been saying this for years now.

But my main point is that in the absence of trade they may have continued to live some kind of simplified sedentary agricultural lives using the same stone tools they started out