Primitive Nutrition 11:
Bad Weather, Barren Lands, Part I
Read some Paleo literature and you'll see they are very invested in the belief that the last ice age would have required humans to eat mostly meat. They think that the climate couldn't have supported carbs. This is an absurd belief on several levels.
This is a graphical representation of temperatures over the last 100,000 years estimated from ice core measurements. The far right of the graph takes us to the present day. You can see why it is believed that prehistoric humans endured much colder climates than today. Earth's history has been characterized by periodic glacial and interglacial periods. But notice, the Paleolithic era experienced extreme climate variability. As this source states, major changes in climate took place within only decades and lasted as briefly as a few centuries.
Computer simulations have been created to clarify regional temperatures during the Last Glacial Maximum. Here you see results from one of these simulations. These maps show temperature changes relative to today (the letters MOD here mean the modern climate). As you can see in the blue and purple areas, some regions were quite significantly colder. However, other regions, represented in red and orange, were cooler, but not dramatically so. Of course, we know that a few degrees of change in the Earth's average temperature are very significant, but for our purposes, we are looking for localized areas where climate might have supported vegetation for human food. I think mean temperatures a few degrees cooler in what are today warm areas hardly creates a situation in which food could only be gotten from hunting big game.
Remember, those were mean temperatures through the whole Last Glacial Maximum. There were also warmer periods during this era. The periods during which climate is relatively warm during an ice age are call interstadials, and there were many during the Paleolithic. Here you can see that during one interstadial, summer temperatures could have been warmer than today in some areas. The region in question here is northern Scandinavia, an area that experienced dramatic cooling during the Last Glacial Maximum.
These scholars are blunt in refuting the perceptions of some about past climates. Claims that this era was harshly cold are false.
What did our ancestors do during the colder stretches? They migrated to warmer areas called refugia. Only during warm periods could they have ventured out of these zones. Those who didn't migrate to warm areas would have faced extinction.
With this awareness, some scholars have asserted the importance of plants in diets of this time. In the past, archaeologists have been fixated on meat, as I have shown you already. Other researchers have resisted this, with one arguing that plants could have composed up to 80% of past diets despite the ice age.
Here, Jonathan Haws succinctly corrects a common fallacy regarding plants in ancient diets. The absence of evidence does not equal the evidence of absence.
Of course, the Paleo diet is not promoted as an all meat diet. However, as I will show you in a later video, some use Paleologic to argue for just that.
What about individuals of European descent? Are their genes so different, as some claim? Do they so clearly manifest a cold-conditioned genetic legacy? Not necessarily. The genetic evidence indicates that those with the oldest European ancestry found Eastern Europe too cold and inhospitable to inhabit at the time. Instead, they migrated to refuges as well, where they intermingled their genes with those of people from more temperate regions.
Here is an example of how gene flow during the Paleolithic affected our present day genetic makeup. West Eurasian, Jewish and some Middle Eastern populations have African genes dating to the Paleolithic. Very few of us have a genetic legacy so clearly conditioned by a cold climate.
I think this abstract is enlightening. It has become clear that there were refuge areas in northern latitudes that could have harbored a variety of plants as well. The Pleistocene epoch referenced here includes the Paleolithic, and it is clear that this era was highly dynamic.
It could be argued that the environmental stresses of the ice age actually drove humans toward agriculture, as plants offered a more reliable source of nutrition, or as The Economist put it, it turned people much more vegetarian.
Taken together, observations from this period weigh against the meat-based Paleo diet concept, I believe. The broad scope of 85 million years of evolutionary history seems built on plants. For that to have been undone during the Paleolithic, selection pressures would have had to have been strong and consistent. Instead, the variability of climate along with migratory patterns mitigating the harshest climate stresses would have conditioned our ancestors mostly to simply be adaptable. As stated earlier, adaptations are not lost unless they become disadvantageous. Clearly, a capacity to find nutriment from a variety of sources would have benefited a generalist species like us.
As we have seen, humans have migrated and followed predictable patterns of dispersal like any other species. This brings me to one of the more peculiar leaps of Paleo-logic - the idea that hunter gatherer populations are appropriate models of diet and health for the rest of us. I start with this slide to establish a principle. Populations tend to expand as far as they can. Reproduction and competition drive this, and humans have been particularly successful in establishing new territories in a variety of conditions.
Sometimes these attempts at colonization fail. We think of circumpolar cultures as masters of survival, fully leveraging any lifeline in their environment. They have to be. We don't see the people who failed to find a way to survive. They're long dead.
It is common sense that such populations could not have had much influence on our genes. They were isolated from the populations that were left to generate our genetic diversity.
When migrants move into marginal new territories and manage to establish a stable population, they can become isolated from their source populations. The collective genetic material of the remote population is no longer influenced by the source population. They are under unique stresses from their marginal environment that affect what traits are selected for inheritance. It is also under these circumstances that genetic drift becomes a key factor in establishing new mutations. This is the same principal as inbreeding. A lack of genetic diversity promotes non-adaptive mutations.
So when Mark Sisson says that in our ever more globalized world there has been more cultural inbreeding and genetic drift, he has it exactly wrong. Where genetic drift is a major factor is in isolated hunter gatherer populations that are the model for the primitive diet philosophy.
Let's look at Sewell Wright's adaptive landscape to visualize genetic drift. The arrow all the way to the left shows the expected direction of selection in favor of fitness. Genetic drift does not move like this. Rather than moving vertically toward a peak in the landscape, genetic drift can be imagined to move horizontally, simply meandering around the landscape without really moving toward greater fitness.
Genetic drift was a factor for all of us, but in Paleo days. Before the out-of-Africa expansion across the world most of the genetic diversity in humans was generated in Africa. Genetic drift came to be a bigger factor during the Paleolithic when genetic diversity was reduced.
Studies of human DNA are suggestive of a major bottleneck during the Upper Paleolithic, in which the total human population appears to have been sharply reduced. Some believe this was due to a massive volcanic eruption that may have driven our ancestors close to extinction.
Whether it was this event or something else that accounts for the appearance of a genetic bottleneck is debated.
In any case, movements of populations out of Africa seem to have been accompanied by a reduction in genetic diversity. In more marginal environments, humans would have had fewer food resources. After all, if the environment necessitated hunting reindeer, for example, variations in the number of reindeer would have threatened these populations. It is under these circumstances, the romanticized Paleo genome conditioning era, that more genetic drift, or more inbreeding, was introduced into the genome. As we have seen, the past ice age did not subject humans to strong and consistent enough selective pressure to undo our African, unclothed legacy. Here we see that efforts to migrate into Europe made genetic drift a greater force.
This seems to have had interesting implications for disease vulnerability. Prostate cancer is over-represented in Northern Europeans. We see that with admixture, or the mixing of genetic material between populations, disease rates change. Native Africans are unlikely to develop prostate cancer. African Americans, whose genes are usually not exclusively African, are more vulnerable.
European admixture also appears to make African descendants more vulnerable to atrial fibrillation.
The same can be said for rheumatoid arthritis.
The stresses on populations in the Paleolithic have left a striking result in our genes today. Amazingly, there is more variation within populations than there is between populations. Once again, we have evidence that at root, what we have most in common is the part of us that is an African from a warm climate.
Further evidence of the importance of our African roots is our tendency toward high blood pressure.
This is because salt retention is adaptive in hot, humid climates with a low availability of dietary salt. The fact that we retain this tendency today argues against our basic nature being best suited to cold climates.
In part two of this video, I'll show you how these issues have lead to one of the biggest flaws in Paleo-logic.
Primitive Nutrition 12:
Bad Weather, Barren Lands, Part II
The first part of this section, in which I looked at the last ice age and genetic drift, just sets us up for an even bigger goof in Paleo-logic.
Loren Cordain acknowledges it is difficult to say what prehistoric populations ate. So far, so good. That should be enough to undermine his idea for a historic meat-based diet, or at least it should cause him to add a few qualifiers when laying out his one and only ideal human diet. But then he makes a huge mistake. He assumes that somehow hunter gatherers are good representatives for all the rest of us. Their dietary practices, regardless of plant to animal ratios, are so diverse it would seem one would not even be tempted to force them into a single template. But that's exactly what Paleologic does. They are all essentially the same as each other, and we are essentially the same as them.
Here you can see that as of December 2010 Loren Cordain was still publishing papers built on this premise, which as you see is itself built on the faulty premise of stagnant evolution.
We can undermine this logic very easily if we look at the big picture. Here you see the locations of the cradles of civilization that took root with the beginnings of agriculture.
Here is a similar map showing where agriculture developed first in orange. If you are watching this, chances are you have a genetic legacy originating from one of these places.
Now look where hunter gatherer populations were in 1950. They are not in areas that supported agriculture and this is not a coincidence. They expanded into marginal lands, and as a consequence, they have remained frozen in time. Paleo-logic essentially acknowledges these people were left in the stone age. Should it be a surprise that they rely on animal foods in marginal lands? Of course not. These places are considered marginal because they have fewer food resources. Look how scattered across the globe they are. They all represent little isolated pockets of genetic drift. To trace back a point in history when they were all together, along with all other human lineages, you’d have to go back to our origins in Africa, the birthplace of the naked ape.
Here is another map of hunter gatherers compiled by Frank Marlowe. This is a wonderful paper.
Primitive populations heavily rely on animals foods simply because animals provide them the only way to extract enough calories from their marginal lands.
This is not lost on Marlowe. He considers them a biased sample, and one that doesn't represent pre-agricultural societies.
Here you see what should be one of the more obvious trends embedded in the hunter gatherer food patterns. As populations move to more extreme latitudes lacking in vegetation, they are forced to gather less and hunt and fish more.
Marlowe offers a further insight into diet and lifestyle for hunter gatherers here. This pertains to the need for camp relocations to be near food. You can see that the more hunting is done, the more movement is necessary. I suspect cultures and economies would be less able to develop in nomadic populations. Fishing is more like plant foods in this regard as it seems to promote sedentism, which is not surprising.
Optimal foraging theory states that hunter gatherers will direct their time and effort to maximize food acquisition. This drives populations toward hunting if calories cannot be obtained in an easier way from plants. It also surely dictates the need to move frequently for nomadic hunters.
Knowing now that hunter gatherers are characterized by relative isolation and marginal ecological niches, it should not be surprising that to the degree our genes do differ, they tend to set us apart from these cultures. FIX
Anyone trying to make an argument for starches not being in compliance with the genome would need to explain why we have adaptations that favor the digestion of starch.
Here you see copy number variations in the human genome for genes related to starch digestion. Notice that groups with lower copy numbers for a starch-related gene are hunter gatherers, while European Americans tend to have more.
In contrast, cold weather populations demonstrate a deficiency in enzymes for digesting carbohydrate.
There are many examples of unique polymorphisms in hunter gatherer populations. Here you see that Inuits, who I will discuss at length in another section, have one that raises their cholesterol.
In spite of their elevated cholesterol, Inuit may have a loss of a functional mutation related to fat metabolism that protects them from heart disease.
This study also finds polymorphisms among the Inuit that are associated with heart disease. These may be signs of genetic drift.
Inuit have been shown to have a high resting metabolic rate. An adaptation like this makes sense for people inhabiting cold climates.
But this is an adaptation you may not want.
Unlike the Inuit, here is a cold weather hunter gatherer population that has a mutation that lowers their cholesterol.
Loren Cordain seems unaware of the importance of the genetic differences in isolated populations. Here he mentions the example of the Ache as supportive of very high protein diets. The Ache are some of the least genetically diverse people in the world.
Perhaps along with their high meat consumption he could point out their low testosterone levels.
The example above them doesn't raise confidence in Cordain's conclusions, either. Spelling "Arnhem Land" wrong is a bad sign from Dr Cordain.
The natives of Arnhem Land have been genetically isolated for almost 20,000 years.
Australian aboriginals themselves are an isolated population, and are therefore more subject to genetic drift.
And the natives of Arnhem Land are among the most genetically differentiated of Aboriginals.
The Paleo crowd is so fixated on primitives, I wonder why they won't go all the way in copying their lifestyles. In the next video, I'll show them how to do that if they want to try real Paleo.