Title: Origins and Evolution of the Western Diet: Health Implications for the 21st Century
Speaker: Dr. Loren Cordain
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.