The following discussion is for educational purposes only, and is not intended to diagnose or treat any disease. Please do not apply any of this information without first speaking to your doctor.Now, let’s head to the show!
Dr. Michael Ruscio: Hey, folks. In this week’s show we are very lucky to have Peter Ungar, who is as high as you get on the academic totem pole regarding evolution. He’s a paleoanthropologist/evolutionary biologist. He formerly taught at Johns Hopkins School of Medicine, Duke University Medical Center. He’s published, he’s consulted for documentaries, he’s studied extensively on evolution. He even has a lab named after him.
So, he is a big cheese in this field, and I was fortunate that I got connected with him via Aaron Blaisdell, who we spoke with recently about gut evolution in the context of determining what the ideal carbohydrate consumption may be today (1). I want to do a follow up call with Peter, who is very well versed in early hominid evolution, dietary evolution.
We didn’t get incredibly, incredibly deep, so I don’t think anyone will get lost. But it’s just nice to have an expert in this field help fact check and help guide is through some of these issues in evolution that aren’t always super straight forward. And he had a few really, really tidbits that he shared with us. It was just a great conversation so I hope you will enjoy it.
Dr. Michael Ruscio: Hey, folks. This is Michael Ruscio. I am here with Peter Ungar, whom I am very, very excited and happy to have on the show. Hey, Peter, how are you?
Dr. Peter Ungar: Hi, how are you?
DrR: Good, good. So, in my last interview, you came very, very highly recommended from Aaron (Blaisdell). So I was happy that you were able to take a moment out and speak with me about hominid evolution. You have a pretty impressive background in the field. Can you give us an overview of what you’ve been doing; what is your area of research and some of that stuff?
What our teeth tell us
DrP: Well, my principle area for my research is the evolution of human diet, at least the first half of human evolution…
DrU: …from the time that chimpanzees and humans split until the time we started to come down to the ground on a regular basis, use stone tools and go hunting and things like that. Basically what I do is I look at the shapes of the teeth of our ancestors as well as the microscopic patterns of wear on those teeth to reconstructed their diets as best we can.
DrR: That’s great. And I noticed you have a lab, the Ungar Lab; am I right about that?
DrU: Yeah, that’s what they are calling it.
DrR: Well, congratulations. That must feel nice to have a lab named after yourself.
DrU: Oh, well, yeah, I guess.
DrR: Since you definitely are the go-to guy in this area, can you come take us through an overview of the evolution hominid lifestyle in diet, and maybe tie in with that how that ties into the evolution of the gut and the evolution of the brain? We have a lot of listeners who are interested in the paleo diet. Certainly, I would say we are paleo fanatics, but a lot of us gravitate toward that. When you are interested in that, you are also interested in the evolutionary background from which some of that developed. Could you give us an outline of how things transpired down the evolutionary path?
DrU: Sure. There are four different grades, if you will, of hominid evolution – four different types of hominids. There are more than a dozen species that we know of to this point; (there are) probably way more than a dozen species. But they really fall into four different groups. The first group evolved after our split with the chimpanzees; we can call these the Ardipiths. This is a group of proto-human ancestors that had not yet come down out of the trees, at least not on a regular basis. They were still living in more forested conditions, in some cases woodlands in Eastern and perhaps Central Africa before the African Rift Valley had spread. They took mostly resources – fruits, young leaves, things of that nature as far as we can tell.
Then the second group shows up around 4.1 million years ago as sort of the earliest representative we have of it. It’s a group we call the Australopiths. That’s represented mostly by several members of the genus Australopithecus. Australopithecus shows some evidence of having had come down out of trees. It spent a considerable of time on the ground, although at this point we’ve got big thick enamel on our teeth, we’ve got hulking big jaws, and we are starting to look like perhaps ancestors that show some adeptations of having come down out of the trees. I can’t tell you exactly what they ate, but at least the shapes of the teeth suggests in addition to forest fruits and leaves when they could get them; things like roots and tubers and shoots and so forth.
The third group is one of the two descendent groups from that Australopithecus group – we call it paranthropus, or the robust Australopiths. The earliest evidence we have for that is about 2.5 million years. And the group survived until about 1.3 million years ago, still exclusively on the African continent. These were a group of highly specialized, at least as far as the anatomy goes, species that had adaptations for very, very tough foods like grasses, or leaves, in a very abrasive environment. Some have said it’s very hard and brittle foods like nuts and seeds, and that’s still open for some debate. Nevertheless, we are looking at intense vegetarians most likely.
DrU: The fourth group, the final group, are the members of our own genus. This represents the second half of this evolutionary fork in the road that began about 2.5 million years ago. Australopithecus gave rise to paranthropus, but at the same time, it gave rise to the earliest members of our genus, the genus homo. And with the origins of the genus homo, we do start to see things like stone tools, and bones with cut marks on them as early as 2.4 million years ago in Ethiopia, which suggest the consumption of a significant amount of animal protein – whether it be meat or bone marrow or what have you – we’re not entirely certain at this point. The evidence suggest that they certainly did take at least enough of that to be preserved in the fossil record.
DrR: Got you, got you. And it’s a really nice fork in the road that you paint there with the paranthropus and the homo fork in the road. I’ve been discussing with Aaron (Blaisdell) the homo habilis vs. paranthropus boisei. I like having that discussion because people have asked, ‘Well, I’ve seen some information showing paranthropus ate a lot of,’ like you had mentioned…almost a specialist in digesting tough plant matter. They were asking me does that mean that we should be including more of that in our diet based on evolution? I said, ‘Well, it doesn’t mean you should or you shouldn’t per say, but I think it’s important to mention that we didn’t stem from the parathropus boisei; we came from the homo habilis, which was a little more omnivorous.’ So, I like how you paint that as a clear fork in the road, because I think it may help some of our listeners sort through looking at some of our ancient diets – or some ancient hominid diets – and try to trace that back to modern day. I don’t think everyone is aware of the fact that parathropus boisei wasn’t one of our predecessors.
DrU: Well, it was our predecessor for sure, but it certainly not our ancestor.
DrR: Right. OK, thank you.
DrU: It was just way too specialized to be our ancestor. What I think is really cool about paranthropus is that they show that there were two distinct groups of hominds walking around the landscape – one of which, when we paint the picture, is this specialized vegetarian. The other is almost certainly taking a broader spectrum diet. But I wouldn’t say parathropus was necessarily a dietary specialist. I would say that it was anotomically a specialist. But it may turn out that the fact that parathropus had this big honking flat teeth with thickened enamel meant that they could take a broader spectrum of foods than their predecessors could. It means they could take the same soft mushy stuff that their ancestors ate, but in addition these very abrasive and tough foods as well.
DrR: Sure, sure. Is it appropriate to say that homo habilis was kind of a jack-of-all-trades, whereas the parathropus branch was – even though they had this powerful machinery that could break down many different food stuffs, they stayed more in the vegetarian realm? Is that accurate to say?
DrU: Well, as best as we can tell. We do have some evidence, starting with the earlier members of our genus, for an increase in the lengths of the shearing crests on our teeth. For a long time, as we go from Ardipithecus too Australopithecus, we see the teeth becoming bigger, the cusps and crests becoming flatter and more bulbus – clearly not well suited for sheering or slicing tough foods, like some plant material and like meat.
But, by the time we get to early homo, we see a bit of a reversal in this trend – the teeth become smaller and the enamel certainly becomes a little bit thinner, and the teeth become a little bit crestier. We see that particularly as we transition from homo habilis into homo erectus.
DrR: So, does the enamel become thinner as you become more carnivorous?
DrU: Boy, that’s a really tough question to answer to answer.
DrU: Why would you evolve thinner enamel? Well, it could just be an artifact of something else. Or itself it could be an adaptation, because when we thin our enamel…if you think about a deer or a cow, for example, they have extremely thin enamel. Their enamel is thin so that they can wear through it quickly, and the edge between the enamel and the underlying dentin is very sharp. That sharp edge allows you to shear or slice through foods. It can be argued that the thinner enamel allowed the same with the early members of our own genus, homo.
DrR: Gotcha, gotcha.
Importance of being omnivorous
DrR: So, the other piece to that that I’ve pulled out from my examination of evolution, and I have nowhere near the expertise in this that you do, so I’m going to fact check everything, all my prior assumptions, with you. Hopefully I am right about most of these things.
One of the pieces that I found interesting was, when we had homo habilis – kind of more of your omnivorous scavenger, you could say – cohabiting along with parathropus boisei – more of the vegetation specialist. At some point, the landscape changed in such a way that vegetation became less available; and the more the jack-of-all-trades was able to live on past the vegetation specialist because they had a more omnivorous diet and they could role with the punches more easily.
DrU: That’s the idea. Of course, it’s hard to know for sure, but the new environmental reconstructions show increase climate shifting – in other words, an increasing amplitude of climate change over the course of time through our evolution. In fact, what has happened is the extremes have gotten more and more distinctive; we’ve gotten greater and greater fluctuations in climate. The basic idea is some creatures are able to handle that. Paramthropus apparently wasn’t, and our own ancestors apparently were.
DrR: Now, do we know what way the climate may have shifted? What I am thinking as I ask this question is one of the things I know that has been shown when looking at macro nutrient composition currently, globally, is that the farther away from the equator you go, usually the more protein is consumed. And, the closer to the equator you go, the more of the vegetative diet is consumed.
So, is it possible that when some of the climate fluctuation were occurring, the climate became colder, and that killed off some of the vegetation? And they were forced more toward animals? Or, is that too much of a stretch?
DrU: I think that is a bit of a stretch. Basically what happened was…well, right now I should say that we are about as cool and as dry as we’ve been, as far as Africa goes for millions and millions and millions of years – probably through most of the Cenozoic, the last 65 million years, it’s been getting I wouldn’t say progressively, but it has been getting on average cooler and dryer. What has really changed, though, are these swings back and forth. We’ve been getting more and more intense swings – it becomes very cool and dry, and then it becomes very warm and wet; and then it becomes very cool and dry, and then very warm and wet. And that’s sort of what we see superimposed on this increasing ampletude of swings, we see a general pattern for cooling and drying. We are…certainly 2.5 million years ago in Africa, it was much warmer and wetter on average over the course of 100,000 years, say, than it is today.
Evolution of gut and brain hypothesis
DrR: And to bring in what the gut and brain looked like during this whole process, a few things that I am familiar with, and I’d love to get you expansion on some of these. Essentially, as I understand it, the gut become, essentially, less complex to free-up energy to grow the brain. Part of the context that I pieced together from the anthropology data is we had, potentially, a longer, more complex, but potentially more highly fermentative gut that could break down more complex foodstuffs, but also required more energy to run. And then as we were able to scavenge more – with the advent of the hand axe, enabling us to tear flesh from carcasses and potentially break open bones to consume the bone marrow – we didn’t need to have as complex of gut machinery to breakdown those foods, so we can shorten the gut, absorb more food, and than have a little bit more energy for growing the brain. I’d love to get your commentary and then maybe expanding on some of that.
DrU: Well, that’s the basic idea. It’s an idea that’s not new; Leslie Aiello and her colleague (Peter) Wheeler came up with this idea many, many years ago. And it’s probably true. But, what I can say is that we don’t have any fossilized guts. So, this will have to remain an untestable hypothesis.
DrU: But logically, it makes intuitive sense that this is what has happened – the brain, beyond a shadow of a doubt, increased. And if you need to maintain an energy balance, one easy way to do it is to shrink your gut as you grow your brains. Something’s got to give, unless you are taking in higher-quality foods overall. We’ve got the end result, right? Our guts are fairly simply compared to a chimpanzee or a guerrilla’s, not that our common ancestor was a chimpanzee; it wasn’t. But it is something to bear in mind. Another thing I would bring up is that when we look at chimpanzees or a guerrillas as our models, there is a real fundamental flaw to that, right?
DrU: Chimpanzees, for example, have been evolving as long as we have from that common ancestor.
DrR: Sure, sure.
DrU: So, the truth is, I mean, 7-8 million years ago, the African continent looked very different than does today. It was much flatter. The forest was much more uniform, and it was much more like woodland. Today, it’s really much more finely divided. In the eastern part of the continent, it’s dry savanna. Whereas in west, you’ve got the Congo rainforest. Back then, there was no Congo rainforest and there was no savanna. It was pretty much flat, level woodlands. And as the African Rift Valley spread, that caused climate change that led to a tropical rain forest in the west, and the evolution of the chimpanzee-like adaptation – spending all of their time in the trees, eating soft, fleshy rain forest fruits – and a hominid adaptation – coming down out of the trees and shifting to a more land-based diet, probably including roots and tubers and meat, and things of that nature. But the common ancestor of the two was certainly not chimp-like, nor was it hominid-like. It was probably somewhere in the middle.
DrR: Uhm. OK, OK. So, something to draw from that, to come a little more current day: one of the points Aaron made – and I’m not sure if this is something you have a lot of familiarity with, but I’d love to get comments if you do – he made a few remarks regarding how Asian populations have been eating Neolithic foods for longer than some European populations; they’ve reported changes or differences in the length of their colon, Perhaps to accommodate some of those Neolithic foods. Do you have any insights on that?
DrU: Man, I wish I did, but that’s about 1 million years younger than my expertise.
Micro biota of the Paleolithic and early Hominid
DrR: Right. I thought so, but I just thought I’d try to sneak that in there. So, one of the other things that I wanted to get your take on was the microbiota of some of these hominids. I’ve seen some papers looking at microbiota analysis from the paleolithic, and it’s certainly a really hot topic right now in research, and also, I think, the general public audience is looking for potentially some answers to their chronic health ailments via understanding the microbiota, and maybe that something potentially therapeutic. Do we know much about the microbiota from the Paleolithic or from early hominid evolution? Any lessons or pieces that we can glean from that in terms of how it affects our brain or our gut or anything like that?
DrU: Not yet. But it’s probably coming. There are researchers now starting to study dental calculus – that is the tarter or plague that builds up and solidifies on the sides of your teeth – often the insides of your front teeth. Those, apparently, preserve traces of proteins if not the outlines of the microbiota themselves. And and there is speculation that some of this stuff will actually preserve some aspects of gut bacteria. And if that is the case – you heard it here first, folks – what you will see is a major explosion of information coming. And people are now starting to look at the calculus on fossil hominids. We’ve already pulled some phytoliths, silica that is found inside of plants, out of the calculus of a 2 million year old hominid. If the people who are looking for gut microbiota are successful, we are going to see a revolution coming the next few years.
DrR: So, tell us more about that. Did you initially say it was dental calculus that they were pulling this from?
DrU: Yeah, yep.
DrR: So how do we get a reflection of the gut microbiota from the dental sampling?
DrU: It’s preserved; it’s preserved in there – it comes from the spit.
DrR: So, what we see in the spit can tell us what’s going on in the colon.
DrU: It can tell us what’s going on in the gut in general, yeah.
DrR: Of course, the oral cavity is an extension of the gut cavity. But I didn’t understand that there was that much of a connection between the two. It’s interesting.
DrU: They’ve had a lot of success looking at Neolithic foragers, for example, and documenting things like milk and cows and so fourth; getting cells of food and animals. It’s definitely on its way.
Dietary mismatch – periodontal disease and autoimmunity
DrR: And that’s a good segue into one of the comments you made to me via email, when we were setting up this interview – how looking at the oral cavity can really tell you a lot about a mismatch bewteen diet and biology. You had remarked that peridontitus is the most common autoimmune disease – which I didn’t fully appreciate the oral diseases as being autoimmune. A lot of what I look at is thyroid and gut and things like that regarding autoimmunity. I didn’t fully appreciate the role of the mouth. So, I’d love to for you to talk more about that.
DrU: Sure. In fact, it’s interesting because my wife is a clinician as well. She didn’t believe it either. Of course, she rarely believes me.
DrU: But, if you start to think about, you realize pretty quickly that plague, bacteria – they elicit an immune response, right?
DrU: When our immune system produces white blood cells, for example, the system releases an enzyme that breaks down connective tissues, and things like the immune system attacks our gums, and the bone lining tooth sockets, in the ligaments that connect our teeth to our jaws. When you start getting these deep pockets, that’s when you lose your teeth. So, periodontal disease is definitely – it’s not so much about the plague bacteria itself, but it’s about our body fighting those plague bacteria and creating this terrible, terrible environment.
DrR: Sure, sure. And it is one of the things that is part of my initial screening, if there is any kind of botched dental work, if you will. Because, certainly if there’s a lingering oral infection, then I am am fairly vigilant about getting the patient to a dentist to get that fixed, because I do think that can absolutely correlate with the other issues that I am trying to resolve, like rheumatoid arthritis, or G.I. disorders – and has been fairly well-documented. I believe the best evidence is regarding different rheumatoid arthritis and oral infections, and there seems to be a really strong correlation there, like you were saying, because the mouth immune system, if you will, can affect the immune system globally. One of the things we’ve been experimenting with is they are now making a probiotic toothpaste. I think it’s early in our understanding, but we’ve been fooling around with that with some patients who have oral issues to see what kind of results they make. I can’t say I’ve seen a lot just yet. But it’s interesting to think that maybe like we have probiotics that we take for our guts; maybe pretty soon we will have some sort of probiotic toothpaste that works works really well in the same kind of vein.
DrU: Huh. Well here is an interesting twist for you: A recent study by match.com asked men and women what they find the most important attribute in assessing the physicality, the physical attractiveness of potential matches. And both men and women, they said teeth.
DrR: Really? That’s interesting.
DrU: Look it up. It’s bizarre but it’s true. Good teeth are considered sort of the most important aspect in physical appearance by many people – it’s the number one, at least for American singles. And what’s interesting about that is that may in part be because teeth are a reflection of our general health status.
DrR: I think that makes a lot of sense. And it reminds me of a survey I came across – this is a number of years ago. But, when women were commenting on men, they remarked that the buns were the most important factor. It was put in some kind of men’s magazine, because men would think, ‘Oh, it’s the shoulders, or the biceps, or what have you, and this is just regarding what body part women found the most attractive. But, it was actually their glutes. And the lesson I pulled away from was there is also this kind of survival window there, because if you look at athletes, usually someone who is athletic going to have fairly good glute musculature. So they could probably run fast, hunt pretty well. And, it’s rare that you see someone who is highly, highly athletic that has really wimpy glutes. And so, I think a lot of our attractions are indexed to things that show survival capability.
DrU: Right. For sure.
The commonality of historical diets
DrR: Let’s see here. There were a couple of other things I wanted to touch on. I guess, to try to tie all of these things home, do you have any recommendations for people – and I know sometimes these things are hard to make, because we are constantly learning more, and opinions are constantly evolving – but are there any things that you think we can do today, in light of this information, to try to be as healthy as we can?
DrU: Well, honestly, you are the physician.
DrU: I study fossils that are millions of years old, so I can’t really make recommendations as to what we should or shouldn’t be eating. What I can tell you is that there are certain things that we eat today that certainly nobody had access to in the past. Another thing I can tell you that there’s no single, and I’m sure you know this, and your listeners know this as well as I do, there is no single caveman or Paleolithic diet. And that people around the world, traditionally, eat all kinds of different things. There are a few common elements that we have. We all cook. There’s not a single living human culture, and there probably hasn’t been one in three-quarters of a million years where there was no cooking. In some cases it was a lot of plant-based foods. In other cases, it was not. I can tell you – I think we are on pretty firm ground and probably in agreement that the highly refined carbohydrates – highly processed sugars, for example – were not available in the past. There’s clearly a mismatch there between our diets and our teeth, and our bodies, in general, and those sorts of foods.
DrU: No milkshakes in the Paleolithic.
DrU: But, as to what we should be eating, I think we are on firmer ground discussing what wasn’t available and what we are clearly not adapted to.
DrR: Sure. Sometimes I think half the battle is just making sure you don’t include in your diet some things that clearly shouldn’t be there. And the more of those things that you can weed out, you are left, hopefully, with a growing list of things that should be there.
DrU: Sounds reasonable to me.
Latitudinal sampling bias
DrR: One other thing before I let you go here that wanted to get your take on was, one of the things that I’ve seen with some of the studies is what appears to be…maybe we can call it a latitudinal sampling bias. It seems like a lot of the microbiota analyses that I’ve seen come from more equatorial regions, and even some of the more fossilized remains seem to come from more equatorial regions, and it doesn’t seem we have a lot of great data, or at least not equal weighting for more equatorial sampling for more polar and sampling. Have you noticed that same thing? Do you have any comment on that?
DrU: It’s true that there has been a lot sampling, for example, on the Hazabe of Tanzinia, or some of the Amazonian tribes. These are the places where hunter/gatherers tend to continue today in a traditional lifestyle – those few that are left. There is little bit that’s been done. Some folks, for example, at Northwestern University have been working in the Arctic – Lapland, for example. But, not a great deal. I think you are justified in saying that for sure.
DrR: OK, OK. All right, sir. Well, I guess we will wrap it up there. Before we part ways, is there anything that you’re working on that you’d like to make people aware of.
DrU: Nope. Just I’m an advocate for evolution, and for evolutionary perspective. And, I’m sure that it can inform us in terms of medicine and health, it can certainly inform us in terms of dentistry, and thank you for at least spreading the word and getting to think from an evolutionary perspective about ourselves, our bodies and where we come from.
DrR: Absolutely, my pleasure. And thank you so much for taking to speak with us today. I know that everyone is going to love this talk.
DrU: All right. Thank you.
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