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Nutrition Past and Future

30 Meat, Brains, and Bugs 


Mark Sisson starts his book by opening up a can of paleologic whoop-ass on the science-based conventional wisdom. Those silly CW-believers say that saturated fat is a heart disease risk factor. (Well, actually they don’t. Scientists say excessive saturated fat consumption might give you high cholesterol and that is a risk factor. It makes no sense to call a nutrient and not something like family history or a behavior or a biomarker a risk factor. But you know what he meant. Let’s give this caveman a break. At least he isn’t grunting.) Look at those little pictures and it is clear that the Primal Blueprint doesn’t wear a tie and it isn’t buying into the conventional wisdom, either. Saturated fat is a major source of calories, this says. Well, no one can argue with that. Saturated fat is definitely packed with calories. The spear-carrying nutrition expert here says that saturated fat has no direct correlation with heart disease. Come to think of it, cavemen never did figure out regression dilution bias or Cox multivariate proportional hazard models. Cavemen never were that good with the abstractions of statistical modeling and few epidemiologists carry spears. The charm of cavemen is in their simplicity. The next point is a very interesting response to the diet-heart conventional wisdom. Saturated fat drove the advancement of brain function for the next two million years. Now that’s an argument against the lipid hypothesis you won’t see in many medical journals. We should eat animal fat out of sheer gratitude for its promotion of the development of our ancestors’ brains. We’d be stupid to stop eating meat now, lest our brains shrink until the world’s last remaining intellectual elites are guys like Mark Sisson and those Paleo dieters hanging out at the local Crossfit gym. Now that is a frightening thought! Maybe we should eat saturated fat!

Before I start eating lard to raise my IQ, I have to admit that I’m a little confused in my current low-fat state. Loren Cordain says it was meat that made him a scientist. But Cordain wanted us eating lean meat in The Paleo Diet because he wanted us to avoid eating too much saturated fat. He called saturated fats “lethal.”

Dr. Cordain is a channeler of cavemen as well and he used to say that saturated fat raises cholesterol and clogs arteries. His ideas were opposed to those of other Paleo gurus like Mark Sisson. It’s only been two million years, fellas. Do you need just a few more years to sort all this out?

Either way, the Paleo guys are all definitely certain you should not go vegetarian because that will deprive you of the calories your brain needs to keep it from shrinking. I always thought that if we ate fewer calories that would result in less fat on your belly, but apparently that weight loss happens first inside your skull if you go vegan. I wonder if they have any research to support that.

Allow me to interpret for the Paleo guys so that you will understand them better. They see that our primate cousins have bigger bellies and smaller brains, and they think this is because they need big bellies to extract energy out of less digestible foods like leaves and bark. The body has limited resources so with all that digesting going on, there is no energy left over to build a bigger brain. This is a strange argument to me since I grew up around carnivorous house cats and they weren’t particularly smart, no offense. Their bellies were kinda small, but I’m not sure eating meat made their brains all that big. I don’t think this holds up especially well even in the context of primates. The smaller primates are the ones that eat more animals and bugs. Are they smarter than fruit-eating bonobos?

I’ve read that bonobos are really smart. I’m pretty sure my family’s cats could never be made to understand words or symbols the way bonobos have.

Now I’ll buy the idea that we have guts that are more proportionally appropriate for energy-dense foods than those of other primates. I suppose that makes us more like carnivores in a way. I thought we were much more closely related to fruit-eating primates than felines, though, so this still doesn't quite add up for me.

Chimpanzees are especially omnivorous primates and even they don’t eat all that much animal food. Looking at this slide, it does seem, however, that humans have needed to develop technologies and cooperation strategies that have enabled us to acquire more animal foods. Put these two ideas together and it seems that our family tree would suggest we aren’t naturally especially carnivorous, and in fact, we had to make some technological and social advances to compensate for that to make it possible for our ancestors to eat more meat long ago. I'm pretty sure Loren Cordain can't unhinge his jaw to take a bite out of an uncooperative wild boar. He'd need tools like guns or crossbows to do that. More likely he just acquires his meat with a tool called a credit card.

It does make sense that even if meat itself didn’t make us smarter, the social complexities involved in hunting would have meant brains had a push to get bigger. Humans would have been better hunters if they could communicate their plans. They would have organized themselves into hunting parties. They would have needed to develop social norms about sharing their meat since they didn’t have refrigerators back then. They also would have needed to be smart enough to fashion hunting tools ...

And indeed, paleoanthropologists define past epochs and cultures by their tool-making technologies for hunting. From my perspective, this means a few things. First, they needed these tools to bring down their game. Technological developments were needed to allow them to eat more meat. Secondly, technology developed really slowly. I can hardly believe how a smartphone can feel outdated after just a year, yet our ancestors needed thousands of years just to figure out how to better turn normal rocks into pointy rocks. Scholars talk about a Clovis culture, for example, because the people back then all made their spear points the same way. There was no Clovis Steve Jobs. They didn’t “think different.”

The Lower Paleolithic was called a period of “almost unimaginable monotony.” The Middle Paleolithic brought another 200,000 years of technological stagnation.

It was not until 50,000 years ago, or perhaps somewhat earlier, that dramatic advancements took place in human culture, advancements that only brought humanity into a more advanced version of the Stone Age. Humans had been anatomically modern, big brains and all, for perhaps 100,000 years at this point. Maybe an argument can be made that the added food option of meat promoted encephalization, which means the enlargement of the brain, because it brought another source of calories to the Paleolithic dinner table, but how can it be argued that meat caused us to become intelligent just by itself? The development of culture, technology, and language that might be called behaviorally modern did not perfectly parallel the enlargement of the brain. Every paleoanthropologist knows we became anatomically modern long before we became behaviorally modern.

Other important factors came into play like sexual selection, sociality, and warfare. All these would have impacted the development of greater intelligence.

As we look across other species, a pattern emerges whereby increased sociality is associated with larger brain size. Among humans and animals, those who could best navigate complex social relationships would have been more successful at reproduction and survival over time. This shows a much closer relationship with brain size than does the meatiness of the diet.

The idea that there was a clear and necessary trade-off between hominid brain size and the digestive system was recently called into question by an analysis across mammalian species published in the journal Nature. I learned about this from the great blog, Paleoveganology. If you are interested in this topic, I suggest you read that blog post and the journal article upon which it is based. Other factors may have been more important, including our ability to get around on two feet and our cleverness at securing a steady supply of food for ourselves, a point to which I will return in a moment.

If Loren Cordain really thinks that eating meat gave us bigger and better brains for nutritional reasons, rather than social or technological reasons, then we should be able to look at his own paper showing plant-to-animal subsistence ratios among hunter gatherers and see that those who have eaten the most meat also have the biggest brains. Do you think Loren Cordain, with his giant meat-fed scientist brain, thought to look for some actual data to support his belief? I don’t think so and I’ll show you why. Cordain published a paper showing that hunter gatherers in colder climates eat more animal foods. That’s a bit of a no-brainer, isn’t it? The Inuit won’t find a lot of bananas inside the Arctic Circle but they will find seals and caribou.

Cordain created a list of hunter gatherers along with their plant-to-animal subsistence ratios in his “paradox” paper that I showed you in the Ancestral Cholesterol section. Richard Lynn wrote a book that was and is highly controversial about race and intelligence. I am not going near his thesis with a ten foot pole, but he does have some data on average intracranial capacities among different cultures that I will use. Now it does seem that the circumpolar people do have bigger brains than do people at lower latitudes. But notice, Europeans are right behind them and they don’t eat like the Eskimos. East Asians are even higher up that list but they have been historically high carb. Meanwhile, the smallest brain volumes are to be found among some of the model Paleo cultures, including the Australian Aborigines, who Cordain says ate a lot of meat. I am not seeing the relationship. By the way, this subtext about brain size and intelligence may be ethically disturbing to you, but this is exactly what Cordain is saying. Meat gives you a bigger brain. A bigger brain makes you smart like a scientist. Meat eating habits should predict intelligence, so cultures eating less meat must be dumber. I think it is simple and self-serving thinking quite like this that produces racism.

I don’t think I am ready to buy this line of reasoning. Brains are just biological computers, and we all know that a computer isn’t necessarily more powerful just because it’s bigger. Maybe Loren Cordain carries around a giant old cell phone because he thinks it works better.

There was actually a natural experiment indicating that there may be other pieces to the intelligence puzzle beside brain size. Neanderthals are said to have had brains at least as big as ours, if not bigger. Yet it was modern humans, with their superior tool making, superior abstract reasoning, and likely their superior language abilities who are still here as the last of the homo lineage. The Neanderthals were such legendary hunters and meat-eaters. Why are they not around to call themselves scientists like Loren Cordain?

Richard Lynn recognized that intelligence and brain size are products of genetic mutations, mutations that were adaptive and were therefore favored for replication. Those mutations would likely have appeared where genetic diversity was greatest, and that was Africa. The Paleo diet pretends to be about evolution, but as usual, the Paleo gurus don’t seem to understand much about evolution. Evolution is about natural selection. Evolution is about genes.

Brain volume is highly heritable in all primates, including humans. “Heritable” doesn’t mean we all eat the same way as our parents. It means we are made of their genes, and those genes govern the development of our brains. New research is revealing which genetic variants influence the size and structure of our brains. Here, a recent study found associations between particular variants and both hippocampal volume and total brain volume.

Like any other mutation picked up along the way, these were the likely result of copying errors, the regular mistakes in DNA replication that have allowed life to diversify. Without these copy errors, not only would Loren Cordain not be a scientist, he wouldn’t even be a mammal. He might just be some boring protoplasmal primordial atomic globule, as Gilbert of Gilbert and Sullivan once wrote.

Genes are in charge of everything else to some degree, so why not brain size and intelligence, too?

To give you a concrete example of this, selective pressure and genetic mutation have been proposed as explanatory of the high IQs and scientific successes of Ashkenazi Jews.

This is not to say that a change in diet wasn’t important or even necessary. If we accept that human brains are metabolically expensive (and they are) and if we accept that a metabolically expensive organ needs extra fuel (and it does), then some sort of increase in food energy would have been helpful. Through their gradually increasing skill at securing a stable food supply, our ancestors took care of that problem.

By adding meat to their diets, they would undoubtedly have done that. This is a simple idea, really. An omnivore has more food choices than a frugivore. Adding new sources of calories probably meant adding more calories overall. Anyone with a dietary restriction of any kind knows he or she is more likely than friends who don’t have dietary restrictions to feel a bit underfed every now and then. The question is, however, was meat the only way food energy was increased? My more dedicated channel viewers know that I like this paper by Rachel Carmody and Richard Wrangham on the potential for cooking to have enabled the consumption of more calories, with all the remodeling of digestive organs that that might suggest. Cooking would have worked in addition to, and not in place of, an expanded homo menu, to promote encephalization.

This quote is in my opinion the only reasonable case that can be made for how meat eating itself might have caused the enlargement of our ancestors’ brains. Snodgrass, Leonard, and Robertson wrote, “These findings do not imply that dietary change was the impetus for brain expansion among hominids; instead, consumption of a high quality diet was likely a prerequisite for the evolution of a large, energetically expensive brain in hominids.” In other words, the genetic process of brain development took place against a background of increased caloric consumption. Today, the genetic results of encephalization have been fixed in place and the maintenance of a high-calorie diet is a problem in the other way – we eat too much food, waste too much food, and produce our food too inefficiently.
Here is John Hawks putting it another way.

HAWKS: And when we look at the fossils of early homo, we see this immediate increase in the size of the body, and also increase in the size of the brain. At the same time we have a real reduction in the size of the teeth. So it’s clear that there’s a diet shift that has happened, and that diet shift giving us more access to energy, has enabled us to have larger brains.

There was an increase in food energy. Most diet books are not being sold to people who need help figuring out how to increase their calories.

Intelligence does not necessarily track perfectly with brain size. Hawks himself has commented in this article on the observation that even as we have gotten smarter, our brains have been shrinking in recent millennia. Hawks speculates that our brains have become more streamlined and efficient even as they have reduced in size.

Richard Wrangham even put forth the idea that the profound reduction in human violence and aggression among our ancestors has indirectly led to a reduction in brain volume. Clearly, there are subtleties in the dynamics of encephalization that the broscientists have overlooked despite their super-smart meat-eating. By the way, you didn’t really think that eating Paleo would make you smarter, did you?

I can just imagine the objections from the meat pushers to all this. It’s not just the calories that the brain has needed. It’s the essential fatty acids. Meat, especially fish, would have been necessary for Australopithecus brains to turn into human brains. Yes, I’ve read that claim. I just don’t think it is a good nutritional argument. The claim is that polyunsaturated fatty acids, like EPA and DHA, would have had to have been provided by the diet, and that means meat and fish would have had to have been eaten, and therefore we should eat meat and fish now. I doubt every portion of that argument. Our ancestors probably could have synthesized all the EPA and DHA they needed. Even if they needed them from the diet, they would not have necessarily required meat and fish for that, and even if we grant the first two propositions, it does not follow that we need to consume meat and fish today. There are EPA and DHA supplements from microalgae for those who want them.

Let’s think about the first two parts of the essential fatty acid argument to eat meat. First, it has not been established that the amounts of EPA and DHA produced by healthy humans eating a varied diet rich in alpha-linolenic acid is insufficient for brain health. Bryce Carlson and John Kingston wrote this article about the role of dietary DHA in our evolution. This is one of those papers that I like so much, I wanted to just read it to you in full but I’ve decided that probably won’t go over well in a YouTube video.

Any claim that fish eating was necessary for encephalization runs up against the problem that archaeological evidence of fish eating does not appear until well after the arrival of anatomically modern humans. The chronology just doesn’t support this claim.

It is worth pointing out that fish do not produce these fatty acids themselves. The original source of them is microalgae. By supplementing with algal oils, you are bypassing the fish and consequently avoiding their saturated fat and toxins, as well as allowing them to live and thrive, and to a brainy person, that should seem like a win-win.

DHA synthesis upregulates during pregnancy, providing evidence that evolution has made it likely the DHA supply matches the need for it when it is needed most. This article has a very good section explaining this phenomenon, including the differing degrees to which DHA is synthesized in men and women. Female hormones appear to deal with the DHA problem quite well.

Of course, as I have said in a past video, there is good evidence that most vegetarians are able to maintain healthy levels of DHA despite its absence from their diets.

This topic creates a bit of an irony for the Paleo people, as one of their model cultures is the Masai. The Masai have not historically eaten much fish. Here, their intakes of EPA and DHA are said to be similar to that of vegans and vegetarians. Consequently, the Masai join vegans as another example of the apparent natural compensation that takes place in the synthesis of these essential fatty acids when they are lacking in the diet. It seems to me that between their low cholesterol levels and their homemade essential fatty acids, vegans are really more Paleo than the Paleo dieters.

That should take care of the first argument. As for the second, if we ignore these observations and assume that dietary sources of EPA and DHA were needed, would that necessarily mean meat and fish must have been consumed by our ancestors? I don’t think so. As I’ve pointed out before, the Paleo dieters seem to ignore the importance of insects as a source of protein and vital nutrients to our ancestors. I don’t see how they can pretend that they are faithfully applying our evolutionary history to their diets while not eating bugs. The Pygmies were observed by George Mann to eat quite a lot of insects along with their sweet potatoes. The eating of bugs was and is quite common around the world.

Insects would have provided an excellent source of polyunsaturated fatty acids, and they have been consumed enthusiastically far and wide throughout our history. Given their historical importance to us and their richness in valuable nutrients, it seems to me insects have not been studied adequately as a food source.

There aren’t many papers like this one, which tells us that one type of ant is an especially rich source of EPA. Which other insects can supply the right essential fatty acids in the diet? Until this is studied, we just can’t say, but that doesn’t mean we can ignore this very likely source of nutrients in the Paleolithic diet.

Another topic I’ve covered already but which I’d like to talk about more is the Paleo argument that humans became less healthy with the transition to agriculture. Did eating beans and grains cause the first farmers’ health to suffer? And if so, why did they do that to themselves? This argument has never made sense to me, and I doubt it will to you, either, after you see the next video.