Primitive Nutrition 9:
Primal Primates, Part I
Paleo promoters say that both the archaeological record and our genes point indisputably to their faddish meaty diet. I'm going to make a counterargument to that, but before I do, I want to make absolutely clear I do not think history should trump nutrition science. If we approach nutrition just through history we are falling for the appeal to nature and the appeal to tradition fallacies. There is more than enough good nutrition science that tells us about the effects of different foods on human health. It seems to me it is impractical if not impossible to recreate past diets, even if we could figure out what they were.
Which diet would we pick? What region? What time period? Would our plant foods be just like theirs or would we be forced to use modern varieties? And would we strictly forbid anything that wouldn't have been found in that time and place? And how would we pick that particular time and place? Was that moment the pinnacle of human evolution? I could go on but I'll stop there.
I think a narrowly historical approach to food is absurd. I am engaging this topic only because it is apparently important to some people. To me this reasoning is just myth making and nostalgia. I have no qualms about looking at diet from a purely modern, purely nutritional perspective. Now that that's off my chest, here goes nothing!
Paleo advocates say archaeologists find evidence of meat eating in all ancient human cultures studied so far, as in this article. Therefore, we are meat eaters who should eat meat. Case closed.
But how much meat? And what about our pre-human ancestors? Cordain doesn't want to get into that history.
Here is an interesting excerpt from Mark Sisson's The Primal Blueprint that ties in to this issue. This might be a good one to pause and read. He is amazing when it comes to sheer density of misinformation. I'll try to correct some of this.
First, as I've shown you, human evolution has likely accelerated more recently.
The distinction he tries to make about how evolution is different now is nonsense. If a trait is being consistently favored in a population, that is an adaptation through natural selection, period. It's not genetic drift.
Genetic drift is not a helpful concept for the Paleo view. It's a bigger factor in small populations, not large ones, so he apparently doesn't understand the term. I'll talk about genetic drift later when I look at hunter gatherers.
Look at that bottom sentence. He is stepping in the teleological fallacy by saying that evolution is somehow directed toward something better. I covered this already. No one who understands evolution would write such a thing.
But I want to focus on one sentence, right in the middle of the slide. He mentions the basic ways we metabolize food, saying it hasn't changed since prehistory. When does he think our digestive organs first developed? When we learned to make a hand ax? Why do all other animals have essentially the same organs as us? Does he think we changed all that much when we split off from other primates?
This Paleo-logic has interesting implications. It's as though we have nothing in common with our closest animal relatives. I find it ironic that the world's most enthusiastic consumers of animals are unwittingly arguing against the scientific value of animal experimentation, as if our digestive organs are totally different from those in chimps.
The Paleo folks should explain their beliefs to the researchers who experiment on animals. Here a German ethics advisory group says animal experimentation has a high predictive value of effects in humans. If we are so different in our basic metabolism, how would that be possible?
The California Biomedical Research Association seems to think primates are an irreplaceable model for the study of heart disease and cancer. Both of these conditions are influenced by diet.
Apparently a high fat, high cholesterol diet - the kind of diet Sisson thinks is good - gives rhesus monkeys atherosclerosis. Does he think research like this was done to figure out how best to feed monkeys? Now you know not to feed your monkey a cheeseburger.
Animals have been experimented upon through the whole history of medical research because of our deep similarities to them. If a high-cholesterol diet does this to a monkey, it might do the same to us.
If you think humans aren't closely related to primates and other animals, here's something to ponder.
This is a human baby born with a tail. Similar events have been reported occasionally in the medical literature.
Here is an abstract dealing with three such cases. Actually, we all have a vestigial tail, although it's not as well-developed as these. We call it our tailbone or coccyx. What do these amazing cases demonstrate?
Once again, Gary Marcus has it right. Evolution does not have the option of doing complete redesigns. Evolution can only build on previous genetic inheritance. Our tailbones prove our ancestors had tails.
Here you see some examples of a concept called homology. You can see that even though all the species pictured are very different, they inherited similar body plans and differentiated from there. Internal organs are also homologous,
which is why biology classes have historically performed dissections, and it's why pre-med students take mammalian physiology. The changes from one form to another represent adaptations through natural selection. The basic body plan doesn't change much, though. It can't because evolution is about small changes over time.
Even if past adaptations are not particularly useful later, they are retained if they are not disadvantageous. This means every organism is a compromise, or a kluge. An adaptation only has to be good enough.
Past adaptations that developed our livers, for, example, have not needed to change much. The liver's basic functions go way back, far enough that it works much the same as the liver in a mouse.
Recently a phylogenetic tree was created to represent all living primates. I think it helps put us in some evolutionary context. The genus homo split off around 2.3 million years ago, but the order of primates goes back 85 million years.
Compare that to the usual date range for Paleo of 10,000 to 2.5 million years.
Here you see the phylogenetic tree created by these researchers. I have circled our position in the tree.
Zoom in and you can see us, homo sapiens. All the primate species nearest us - chimps, orangutans, and bonobos - eat plant-dominated diets.
Our closest primate relative is the chimpanzee. You can see here that chimpanzees eat a highly varied plant-based diet that relies heavily on fruit. Our evolutionary path split from that of chimps between five and seven million years ago.
Fast forward in evolutionary history to the hominid Australopith genus, which were almost certainly direct ancestors to all homo species.
The Australopiths were not pre-adapted to eating meat.
You can see where the important hominid finds were made, including Australopiths. There can be little doubt we originated and spent most of our evolutionary history in Africa.
Before their migration from Africa our ancestors, were able to survive without either clothing or body hair, which should tell us something about the warm temperatures they experienced. This date takes us through the development of anatomically modern humans. Think of what that means for food. Remember this when low carbers suggest you should eat like an Eskimo.
When it comes to nutrition, we are fundamentally African.
Reading the literature on early humans, it is clear to me that we need to be comfortable with a certain level of uncertainty. There is some debate, for example, about how humans got to Eurasia.
You can imagine what a challenge it must be to piece together human migrations going back 75,000 years. It seems this history isn't established well enough to support a fallacious appeal to nature, if you really want to go that route.
Neanderthals provide a good example of our hazy view of past diets.
As you may know, they have mostly been depicted as top level carnivores. However, it is now clear that they ate plant foods. It is quite interesting, I think, that even these extreme meat eaters have been shown to have eaten legumes and grains. Maybe Loren Cordain thinks they went extinct from eating too many lectins.
Samples demonstrating these foods in their diets are around 35,000 years old.
These researchers find little support for a believe that our ancestors relied on specific foods, contrary to Paleo beliefs. The adaptation was not to meat, but to ever greater variety, and I think that is the bottom line. We succeeded because we are adaptable.
They lay out some of the difficulties with trying to reconstruct past diets. Small sample size is most problematic, but they all obscure our view of the past.
These and other issues may have lead to a systematic underestimation of the use of plant foods, as I'll show you in part II.
Primitive Nutrition 10:
Primal Primates, Part II
In part one of Primal Primates, I explained that it is too difficult to piece together past diets to be confident we know the truth about what ancient humans really ate. Plant foods are especially hard to account for in archaeology.
Unfortunately, one of the reasons plant remains have not been mentioned in fossil studies much is because researchers have not always tried to find them.
It seems strange to assume that plant foods were not exploited extensively throughout the history of homo. The processing of plant foods has been observed in chimpanzees and in modern hunter gatherers. Why should this not have been the case for all the stages of evolution in between?
Plant foods that were likely important components of past diets were not preserved in the fossil record because they decompose so easily.
This has lead to what is probably an overemphasis on meat-eating by our ancestors. The more contemporary researchers look for evidence of plant-eating, the more they find it.
This scientist believed evidence of carnivory may tell us little about the overall importance of meat in past diets. He thought there was some bias in past interpretations of diet toward meat-eating. I'll add that endeavoring to concoct a fad diet out of fossils introduces the possibility of bias as well.
Loren Cordain personifies that bias. Here he makes the familiar argument that meat allowed for our big brains, or our high degree of what is called encephalization. He says he wouldn't be a scientist if humans hadn't eaten meat. He is therefore a scientist who is apparently completely comfortable with the appeal to nature fallacy. Maybe my brain isn't as big as his, but this raises some questions for me, the first being, so what? Why does this mean we should eat meat now? Is our environment the same as theirs was? Did early humans have easy access to high quality grocery stores with a diverse year-round selection of beautiful produce? Does he think he is growing his brain if he eats a steak today? And is the science really so clear that it was the meat and not the practice of cooking that fueled the growth of our brains?
It is not at all clear that it was meat consumption that lead to our split from other primates.
These researchers find homo encephalization to be better explained by the consumption of underground storage organs like potatoes.
They say it is not clear how much meat the homo genus ate and why.
Here you can see a recent assessment of the vegetation that existed through the last six million years or so. One of the authors accepts the idea that meat was important for encephalization. However, his quote at the bottom is representative of a disinterested scientist, as opposed to someone with a diet book agenda. He says,
"Anybody who isn't confused doesn't know what's going on."
That's a real contrast to absolutist Paleo rhetoric.
Cordain also fails to consider the role culture might have played in the development of bigger brains.
The best thinking I've read on the effects of hominid diets on brain size has come from Richard Wrangham of Harvard's Department of Human Evolutionary Biology. In this article, he and Rachel Carmody make a powerful case that the uniquely human practice of the cooking of food would have provided the necessary energy to grow our big brains. This section on raw diets is especially interesting. Raw dieters tend to have relatively low body mass. Raw foods, whether meat or plant, could not have provided the surplus of energy needed for encephalization.
Let's think about encephalization another way. Here Loren Cordain says lean meat is brain food, without which we would have brains like chimps.
The argument he puts forth is that eating meat gave our ancestors more food energy. He says energy because he doesn't want to say calories. If he did say calories, the flaws in his Paleo-logic would be plain. So meat gives you more calories. Is that why people buy diet books, to find out how to eat more calories? And if excess calories are what made big brains possible, why would lean meats be the choice over fatty meats? After all, protein and carbs are both 4 calories per gram and fat is 9 calories per gram.
Actually, if you accept other Paleo talking points, lean meat would give you less net energy than carbs because it is thermally inefficient and because it ruins your appetite. It seems to me Cordain isn't being logically consistent.
Maybe this dilemma with calories is why he adds DHA to the argument. He doesn't develop the thought, but instead, in the same paragraph, he says early humans in England were top level carnivores like wolves. This was 12,000 years ago. Isn't that too recent for adaptations to food according to him? And what about humans everywhere else? And how healthy were these people in England? And is he saying the Paleo Diet concept tells us we should eat like wolves? Why then doesn't his diet look like a wolf diet? I guess you need to be a primitive to understand him.
All this should give pause to anyone trying to justify their diet strategy through runaway speculation about evolution. It's far too easy to concoct a just-so story to justify the ideas for a fad diet book. I’ll concede there is one way meat eating may have caused brains to grow a little bit. It must take a lot of grey matter to make up so many excuses to eat meat, while avoiding all the obvious reasons we should not.
One part of the fallacy-ridden argument for meat eating is the claim that the last ice age would have required our ancestors to follow a carnivorous diet. This very weak line of argumentation is addressed next.