Title: Origins and Evolution of the Western Diet: Health Implications for the 21st Century
Speaker: Dr. Loren Cordain (Full Profile)
Video Source: YouTube
Dr. Loren Cordain – Author, The Paleo Diet
Wow! What a warm welcome. Thank you so much Pensacola. So I want to thank Dr. Ford for the cordial invitation down here. Also I want to thank Roger and [Orthane] their courtesy for providing me with the house. So very much appreciate it. So let’s just go ahead and get into it.
This talk is based on a scientific paper our research group published in American Journal of Clinical Nutrition in 2005 [http://ajcn.nutrition.org/content/81/2/341.full], and to say the least I’ve got an incredible mileage out of this paper. It’s taken me all over the world. So as a matter of fact, I’m going to be — where am I going to be — I’m going to be in Rome in two weeks giving a similar talk. So lot of mileage on this.
All right. So any time we’re talking about the origins and evolution of the human diet, what we’re really talking about is the origins and evolution of humanity itself. And so let me walk you through this slide because this is going to set the stage for the rest the lecture. And if you look carefully up here, there’s a couple of key items that we need to consider.
The first thing is the word “Hominin” and what hominin means is a bipedal ape. And so what all of these little boxes here, these rectangular boxes, represent are hominin. So these are different species of our ancestral humans, and the length of the box indicates the time in the geologic record in which we find these fossils. And so these ones that are labeled in green right here, we’re not sure if these are apes or if these are hominins. So these are kind of the last common ancestors and you notice then that the period at which we became hominins and bipedal happened roughly 5 million to 7 million years ago.
And as we move in this direction, you can see these pink boxes represent our own genus Homo. And so as we move further on up, you can see that here is homo sapiens. And homo sapiens, our own genus and species, only have been around for about 200,000 years. And there are no other hominins that are left, we are the remaining ones.
There’s two key periods that we need to consider for this lecture. And one is the Pliocene. The Pliocene goes back to 5 million years ago and then we need to look at the Pleistocene. The Pleistocene happened about 1.7 million years ago on up to the present. And this is when really all the action happened when we became human. And so we believe that diet was one of the environmental factors, perhaps the most important environmental factor that allowed us to become human. And we’re going to get into this issue with the lecture.
So there may be as many as 20 hominin species that existed. They simply did not have one diet. We talk about the Paleo diet, or the Paleolithic diet, the Old Stone Age diet. There really wasn’t one diet and that diet varied by geographical locale, season and other factors.
So let’s talk about that period — the Plio-Pleistocene and what do we know about that period for sure. So we know that our ancestors ate an omnivorous diet. They ate both plant and animal food. The difference between their plant and animal foods compared to ours is that they were wild and unprocessed. They simply did not have the technology to process their foods. So these are some really cool photographs taken by Richard Lee at Harvard and these photographs were taken of the Kung people in the 1960s and – late 1960s. And so if you look carefully up here, I know the people up front can probably see this. But this fellow actually has a stone tool at his hand and this was an experiment to see if you could butcher African animal with the stone tools and it turned out they were very effective tools at butchering and disarticulating the carcass.
If you look up here now these guys are sitting around doing nothing and of course the women have gone out and gotten all the food. And so we’ve changed so much, haven’t we? So you can see right here, if you take a look carefully, I know in the back it’s going to be a little bit more difficult, if you can dim the lights but I guess we cannot. But you’ll be able to see that — look at the size of her fist right here and then look at the size of this thing that looks like a watermelon, it’s a tiny little watermelon and indeed that’s where watermelons came from, they’re indigenous to Africa. So she’s gone out and collected these melons. These are called tamma melons. And if you notice over here, here are some berries and here’s some roots right here. And see the stick that’s how she dug up these roots, is with her little digging stick. And right here in the middle, I guess you can see it, I’ve given it away but that’s a tortoise. So when women go out and gather they get both plant and animal foods.
So what can we say about the Plio-Pleistocene diet and how do we know that it was omnivorous? What is the evidence to support that notion?
We look at our closest living ancestors, that last common ancestor about 5 million to 7 million years ago, probably didn’t look a lot like a chimpanzee and it didn’t look like us. It looks like something in-between because chimps have evolved as well. But chimps are primarily frugivorous, they eat a lot of fruit in their native environment. But they also eat a lot of meat during the dry season. And if you look carefully right here, this is a male chimp and they go out in the forest in packs, probably four to seven males or even more and they chase around these little colobus monkeys and they also chase around small antelope. And they catch them with their hands but they don’t have large carnivorous carnassial type teeth to be able to tear apart the flesh. And so how they kill them is they body slam. They grab them and then boom, they pound to the ground and then it takes them forever a day to disarticulate the carcass with their small teeth. And they literally eat everything. They eat the brains, the break open the bones and eat the marrow and eat the meat and so forth. So they eat close to a quarter pound of meat a day during the dry season. So that is indicative that perhaps all hominins were meat eaters.
This is even more powerful data. This is a stable isotope data. And if you look carefully up at this fossil. This is one of more famous fossil. This is called the Taung Baby. And you see that if you look at the teeth right here, the enamel is still intact on the teeth and because of that it allows us to go into this tooth and measure an isotope called delta 13 carbon. And by analyzing this isotope we can determine what this particular creature has been consuming. And so if there’s more of these C3 type foods, this is a browser. This is an animal that consumes the leaves, shrubs and herbs and if there’s more of this C4 isotope, it’s consuming more grass, because grass has a different photosynthetic pathway than do herbs. And so the signature that ends up in the carbon of the tooth is different.
And so if we look at these blue squares right here, these represent — these are members of Homo, or own genus. And these are hominids that came before Homo. And notice that their signature falls halfway between browsers and grazers and it’s quite similar to obligate carnivores like hyenas and lions and these animals that are now extinct. So animals that eat these other animals, if you’re a lion or a hyena you’re going to eat both a browser and grazer and that’s why they have a mixed signature. And so the interpretation here is that these guys were also eating both plant and animal foods.
So this is the uncertain part of the diet as how much plant and how much animal food were being consumed. And let’s go back to that original diagram and what we can say is starting in about 2.5 million years ago and it’s somewhat coincident with the evolution of our own genus Homo where there’s evidence to show us that we’re starting to eat more and more meat. And I’ll show you that’s probably one of the key environmental factors that allowed for large metabolically active bring to evolve.
So what is that evidence? If we look in the fossil records, stones don’t leave us. Okay, they’re basically here almost forever and these are stone tools that were unearthed in Ethiopia. And this is the guy that actually found them. And if you look carefully up here, you’ll see there’s two types of stone tools. They are the sharp flakes and the sharp flakes is what these guys are really after when they’re making the stone tools. They can be used to disarticulate a carcass and modern-day experiments show that they’re very effective at cutting open skin and getting muscle and bone away from the carcass.
The second part is this core which is results — it was the result in part from this chipping process. And this is effective at smashing open skulls and getting at brain tissue. It’s also effective, if you put it on a animal stone and getting at marrow. So we think that marrow and brains were some of the key dietary factors that allowed us to become human.
This is one of the most cool fossils ever found and this is the jaw bone of either a hartebeest or wildebeest. And if you look up here there’s a little scratch mark and if we magnify it with scanning electron microscopy, there’s a very characteristic mark that is not a [Nam arc] from another carnivore nor is it a stone mark that happened to randomly scratch this while it was being fossilized. So we know that this is indeed a cut mark and it’s on the medial side of the jaw bone, meaning the inside. So what do you think they were after? Yeah, they were after the tongue. And so work from our laboratory shows that the tongue actually is a high source of mono-unsaturated fats which are healthy fats. And the same thing is true with marrow is when they cracked open the marrow they were also abstracting a food that was also very high in monounsaturated fats. So these are very healthy fats in terms of what they do for cardiovascular disease.
Expensive Tissue Hypothesis
Okay. Here’s another very intriguing bit of evidence. This was the so-called Expensive Tissue Hypothesis and this was invented by my colleague Leslie Aiello at the University College in London. And this paper came out in 1995. And if we look at our brain size and we contrast it to our gut size, we have incredibly large brain, and we have a very small gut. If we were to look at all other primates, monkeys and apes and so forth, and we were to predict what a 65-pound or 65 kilo primate ought to look like, we should have a very large gut and we should have a small brain but we don’t. And so the implications of this – there was an evolutionary trade-off to evolve a large brain at the expense of having a reduction in our gut size. And so this is how we interpret this, is if you look at the slide and you envision a brain – “a brain is the hottest organ we have”, metabolically it uses more ATP than any other organ in the body, about 9 times — as you’re at rest right now 9 times the amount energy is devoted to running that brain.
So think about it, if we had a brain that was filled our entire body, my God, our metabolism would be out the roof, wouldn’t it? And so this is the key to understanding this Expensive Tissue Hypothesis is that we actually measured our overall metabolic rate and guess what it turned out to be the same as all other primates. So inferred on that was the notion that another organ’s metabolic rate had to decline and indeed that’s what happened. So we started to have this — we had selection for smaller gut which allowed for the selection of a larger brain.
Well, how did that happen? Remember what the diet of the chimpanzee was primarily fruit and plant-based food. So as we started eating more and more meat in our diet which is more calorically dense, then that was the selective pressure that allowed us to evolve a larger brain.
Origination of Hominids
So here’s some really interesting data. If we look at where all hominids actually originated, they originated in this East African area here, all the way down to South Africa on up to Kenya. And the origin of Homo, our own genus, occurred about 2 million years ago. So this is a very cool fossil that was found 1.65 million years ago. But notice that the first fossil of hominid found in Europe was found in this place site called Dmanisi site in Georgia — present-day Georgia and it’s dated to 1.8 million years ago. So what that tells us is that our own genus somehow had to have gone further north. And so the idea is that we either walked down the Nile and we crossed right up here and then we went up through this Black Sea area. The Black Sea actually didn’t exist then. And this is how we got to 40 degrees north latitude.
Now I don’t know about you folks here in Pensacola but I live in Colorado, right 40 degrees north latitude right now and the ground is still frozen. There’s no food. So you are at 4G, you’ve got to have animal food as a major source in your diet. So the behavioral adaptation to either to hunt or to scrounge animal food had to have happened at lower latitudes before we could have got here. So even during the interglacial periods, you had to have animal foods to live at these very far north latitudes.