Is paleo the key to better health? What it gets right, and the 5 ancient diet claims that are dangerously wrong with Dr. James Cole and Dr. Federica Amati

We all want to eat healthier. The Paleo diet promises exactly that: eat like our ancestors, avoid modern foods, and improve your health. But does it really support your gut, heart and long-term health,, or is the story more complicated?

In this episode, Dr James Cole, a world-leading expert on prehistoric diets, joins Dr Federica Amati to explore what Paleo gets right and why some of the claims may be dangerously wrong.

James explains what ancient evidence tells us about human diets, why the modern-day Paleo diet may go too far in its restrictions, and what that might mean for your heart disease risk and gut health.

Could trying to eat as our ancestors did force you to cut foods your body actually needs? Before you give up grains, beans or dairy, it may be worth asking what ancient humans really ate.

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Jonathan: James, did our ancient ancestors mainly eat meat?

James: No.

Jonathan: Did Paleolithic humans all eat broadly the same diet?

James: No.

Jonathan: Is it true that during the Paleolithic, our gut evolved to be smaller?

James: Yes.

Jonathan: I'm smiling before I even ask this one. If we wanted to eat like our paleo ancestors, would our diet need to include cannibalism?

James: Sometimes.

Jonathan: We've never asked that question before on ZOE. And Federica, there's a modern diet that's been very popular called the paleo diet.

Jonathan: Are some aspects of the modern paleo diet healthier than the average Western diet?

Federica: Yes.

Jonathan: Is it easy to get all the nutrients that you need by following the modern paleo diet?

Federica: No.

Jonathan: And finally, James, what's the most common misconception that you hear about the Paleolithic era?

James: People think that the Paleolithic is just about cave people in skins, you know, in clubs, and kind of walking around the entrance of a cave, and that's really not what that whole three to seven million year period of evolution is about, really.

Jonathan: So look, I think that's fascinating and, you know, in a way we're covering two things here at the same time that fit. So one is actually understanding sort of what our ancestors lived, how they experienced things, and the fact that scientists in the last few decades have made these amazing breakthroughs in terms of understanding what our ancestors really ate, which seems extraordinary 'cause it's so long ago. But the other thing that ties into this is that there are a huge number of people who swear by this modern paleo diet, and so I'm really excited to learn more about what that is and how healthy it is and how it sort of fits with what we ate in the past, because this big claim about the paleo diet is it's sort of going back to what humans ate in this Paleolithic era. And so this is really fun to have you here, James, talking about the past, to have Federica, our amazing scientist and nutritionist, talking about, like, what does this modern diet really do? But let's start at the beginning. What is the Paleolithic? 'Cause I've used that word multiple times, and I'll be honest, other than thinking about something to do with, like, cave people- I don't know anything about it. What is it? When was it? Could you help me out?

James: The Paleolithic in its literal translation means Old Stone Age. So if we're talking about the Paleolithic, we're talking about when we start to see stone tools enter our evolutionary record. But- The addendum to that is we've been evolving for much longer than we've been making stone tools. So we last had a common ancestor with chimpanzees sort of about seven million years ago. We take two different evolutionary branches, and we evolve independently of chimpanzees over seven million years. And then stone tools, so the start of the Paleolithic, start to enter the record, at least from our current knowledge base, about three point three million years ago. And then stone tools stay with us really all the way up to the present day, from there. But our evolutionary trajectory from the split with our last common ancestor is a seven-million-year sort of story that we only know very fragmented pieces about.

Jonathan: Amazing. And so the Paleolithic is from that 3.3 million years ago- From that 3.3

James: million, yeah

Jonathan: all the way up until-

James: Now. People still use stone tools and kind of make them and, in different indigenous communities around the world and things. So it's never left us. Once we start making stone tools, it's kind of a recurrent part of our technological and behavioral journey.

Jonathan: And where were our ancestors living on Earth during this time?

James: Yeah. Okay, so there's quite a lot of interesting debate around when and where this kind of split with the last common ancestor occurred. So the bulk of the evidence by far and away points to an African origin, and that really stays true even to our own species, Homo sapiens, that emerged about 300,000 years ago. We're African really in origin. But as always, with like other animals, we move about and we disperse and, you know, the world is largely empty of kind of human-like creatures for really up until the last few thousand years where you kind of start to see big, big masses. But Africa's generally an origin point, then you can move out of Africa into the Near East, into Southeast Asia, into Eurasia. But there are always different evolutionary tweaks that happen on the way, which mean that some of our hominin ancestors evolve independently outside of Africa as a result of these very early dispersals, and then we later species kind of meet up with them and link up with them, and we carry their DNA in us today.

Jonathan: 3.3 million years is a long time. Like, we weren't even Homo sapiens- No ... 3.3 million years ago. No, no, not at all. So how far back can we go when this still feels like this might be relevant to thinking about, like, how a modern human being might think about how they live and what they eat?

James: Yeah. Biologically speaking, you can sort of think about a body plan or a bauplan that might be broadly recognizable to our own. So if you saw them walking down the street dressed in clothes that we're wearing today, you might think, although slightly different looking, but kind of human. Homo erectus is kind of the first one that you might think is kind of about our height. Their brain size is a bit smaller than ours generally. So Homo erectus about two million years ago, it kind of evolves, but it's quite a long-lived species. It's one of the longest-lived species.

Jonathan: And so how long have there been Homo sapiens?

James: So Homo sapiens starts to emerge in the fossil record, about 300,000 years ago.

Jonathan: Only 300,000 years ago?

James: Yeah, and that's the oldest fossils that we have, and it ties in quite nicely with the oldest kind of stone tool technologies that we also associate with the emergence of our species. And what's interesting about the emergence of Homo sapiens is that quite often it's thought that we just evolved in one place. So either... And normally, that place is either pegged as East Africa in the Rift Valley kind of system in Ethiopia, Kenya, and Tanzania or in South Africa. But five or six years ago, Eleanor Scerri and colleagues brought together this idea that actually our evolution was not tied to a single place in Africa, but as a Pan-African evolution of Homo sapiens. So we sort of appear on the African continent, across the African continent, broadly the same sort of time. So these aren't all connected societies, but it's sort of just this general emergence at about three hundred thousand years ago. And certainly when you look at the ancient DNA evidence and mitochondrial DNA, all of that points to Africa being the origin of our species. So at heart, we're all African.

Jonathan: I'd love to come back now to the quick-fire question talking about diet. Right. And you said that actually human diets were not the same everywhere, you know, even- Right ... back so far. How can you know anything about what our ancestors ate so far back in time?

James: Yeah. So we definitely know they ate meat. The most common evidence we have for meat eating is the fact that we have cut marks from stone tools on animal bone- across different sites, and that goes back almost two million years are some of the oldest confirmed cut marks that we have from stone tools. So that's where you found fossilized bone. You can see these kind of striations on them, and when you look at them, under a microscope, you can see from the type of groove that it is whether it's made from a stone tool versus, say, an animal hoof or trampling or something like that. So you can actually see that humans have modified the bone. And those cut marks occur when they're cutting through the flesh and then accidentally are nicking the bone as they're kind of moving the hand ax or the flake to kind of go through.

Jonathan: How do we know about anything else that we ate other than meat? Yeah.

James: So when you can analyze the buildup of the teeth, what chemical substance are being incorporated into that buildup through the isotopes, you can start to see that it's not just meat. You can start to pull out things like carbon signatures. So you can see that they're eating plant foods, grasses, sedges. And some Neanderthal remains have even found things that are linked to, I think it's poplar bark, which is the base ingredient for aspirin. So there could be things around self-medication. It's like when you go to the hygienist and they clean and they scrape your teeth and flick all the bits off, that's the stuff that we're interested in to understand what people were eating. And

Jonathan: does this mean that our ancestors didn't have very clean teeth or- Well, they- ... that you're very good at finding the remains?

James: They didn't have access to the same dental hygiene we do, but amazingly, they did actually, or at least Neanderthals did take quite good care of their teeth. So there's clear evidence from the scratches on their teeth that they were using toothpicks to kind of clean their teeth. And recently, there was a study a couple of weeks ago that showed that they were doing some minor dental surgery on some of their teeth. So the Neanderthals really actually had comparative to homo sapiens, had quite good teeth care, whereas our species didn't really in the early days have a comparable level of dental hygiene.

Jonathan: Our Neanderthals have been unfairly maligned. I...

James: completely. Yeah

Jonathan: How does this evidence allow us to understand, you were describing this idea that diets were not the same-

James: Yes

Jonathan: everywhere.

James: Yes. So what we can then do is through the understanding of these kind of chemical signatures of what's building up on the teeth and the bones and things, you can start to then also match that to the chemical signature of the environments that they're in. And that's how you can understand, for example, when we apply this to migrating herds of mammoths, that they were born in one area, and then they've migrated across the European continent to another area where they've eventually died, and you can track that journey through these chemical signatures. So you can do the same with hominins. You can see where they've been, how they've moved through those environments, as well as kind of what they eat. And that allows us to start reconstructing a bit about mobility patterns, but also about how wide and locally adapted their diets were. The other thing we can do is look at fossil remains and these tooth remains in different places and see what the diet constructions are in those different places. So just to go back to Neanderthals, for example, there's a very famous Belgian cave called Spy where some work was done on some of the teeth there showed they had a very high nitrogen trophic diet, which are very meat-based. But the Neanderthals in Spain almost had no meat in their diet, and they seemed to be eating things like mushroom, moss, and other kind of grass, plants, and things like that, that were around. So they're clearly then adapting to the environments that they're in and making the best use of those local environments and resources. It's entirely dependent on where they are. So for example, Neanderthals at a site in Gibraltar, we can see that they were exploiting a marine diet versus a meat or plant-based one. So it is just where they are. These hominins seemingly depend, doesn't really matter what species they are, but they are really adapting to those environments.

Jonathan: Could you describe to the best of our knowledge today, like what did our diet look like and how does that compare with this image I had that it's like- Yeah basically all wooly mammoth steaks- Right ... every day cooked on the fire because that's what the fire was for.

James: The reason why we have that idea in our minds is from a couple of, yeah, this caveman iconography that was kind of constructed in often newspapers and things like that to kind of show these other human ancestors as being something less than us. When Darwin was first talking about evolution and origins and that we might evolve from primates, people didn't like that because humans like to think that we're special to the rest of the world, right? So this kind of demonization trope, this kind of less evolved, kind of dumb ancestor is part of that story. But as our scientific techniques and knowledge grow and expand over that kind of hundred-year period, our information grows, and therefore we have to change our understanding of the past. But the meat-eating one comes from a very early isotope study that showed that Neanderthals seemed to eat more protein, high-quality protein than hyenas, so they placed them at a higher kind of trophic level when it was all plotted out. And that kind of gave birth to this idea that our ancestors just ate meat. What we know now though is that there's meat there, but there's also carbohydrates, and carbohydrates are pretty important in terms of our life cycle and our need to kind of stay healthy, balanced and to, and reproducing things. You couldn't just do that if you were just eating meat all the time. So what we can see with our ancestors, Neanderthals, us, Denisovans, others, is that they are eating a range. It is not just meat. There's meat, but there's also plants there. And the other thing to bear in mind is that some of the stuff is seasonal, so some parts of the year they might eat certain types of meat more frequently, or certain types of plant more frequently. And then as the seasons change, their diets will change and shift, depending on where they are. And they might migrate to maintain a link with some of the animals, or they might stay where they are and kind of exploit whatever comes into season new. So it really is ... When I think about the paleodiet now, it is about kind of local, and I'm talking about the Paleolithic, not our modern paleodiet, but it's about kind of local adaptations to those conditions and just making the best of their knowledge of the natural world, and then exploiting that as much as they can.

Jonathan: If I understand what you're saying is one of the things that's maybe a little bit special about humans is that we're evolved to be able to eat a very- Yeah ... varied type of diet. Is that right? That that's quite different from maybe, you know, gorillas- Yeah ... or other apes.

James: Our great evolutionary sort of leapfrog moment is the fact that we are, and I'll use a term, we're quite plastic in terms of just, not just cognitively. So our big brains give us the ability to think our way out of situations and adapt, but we're also able to adapt physically to different environments. And we can do that because within our evolution trajectory, we sort of operate under natural selection for the first kind of few million years. But then once we start to kind of create material culture and take control of that and use that to hunt, to exploit the natural world, to kind of enable us to move, we stop being beholden to the rules of natural selection so much and become much more under cultural selections. Things we do start to be kind of determined by what our society wants us to do and kind of think in the norms. And that then means that we start to be very adaptable because we have to kind of play two fields at the same time, the social realm, as well as the kind of physical, making sure we've got enough food and rest and everything else that we need. So what that then means is that different groups might culturally define a different diet that they want to do and then persist in. And then the other element is that mix of diets then kind of starts to play a role in, not so much in the later part in terms of how our physical bodies start to evolve and change.

Jonathan: So you mentioned like the evolution of the gut. How has that changed compared to our ancestors? And I've got this thing that somebody told me that, you know, you can tell the difference between like a carnivore and a herbivore based upon sort of what's inside their- gut and the length of things like this. So what are we evolved for- Right ... and what happened through this Paleolithic period?

James: So if you think we are primates, so what we should do is have really large stomachs like gorillas and chimpanzees do. They have really big stomachs because the food they eat is also quite hard to digest. So they've got big chomping teeth to kind of get through all of that vegetative matter, and then it takes time to process in their stomachs. What's happened in our evolution trajectory is that our stomachs are about 20% smaller than they should be for a primate of our body size, and our brains are about 20% bigger. Now, in terms of that evolution trajectory, growing and shrinking organs is a really energetically expensive business, so there's got to be a really strong selection pressure for evolution to kind of go, "This is a good idea, and we should kind of persist with this." And it's also not an overnight thing. This is gonna happen over a very, very long period of time, hundreds of thousands, millions of years. I mentioned earlier that we split from chimpanzees about seven million years ago. We would have had a body plan, and a stomach, and a gut size pretty similar to them presumably at that point. And then before we get to our species, what we go through is a series of other hominins. The most well-known will be the Australopithecus or the australopiths. One thing that we can see with the australopiths is that they are sometimes termed what we call these transitional fossils. So we can see that they are bipedal around the shape of their hips and their legs. But they maintain what we call arboreal adaptations in terms of the length of the arm and the length of their fingers. So they're still tree climbers, and Lucy indeed may have died by falling out of a tree and breaking her collarbone. But what's interesting as well is that you can... from the fragments that we have, you can see that the shape of her ribcage is changing, and that also means the shape of her gut's changing. So the gut is starting to become a bit smaller as we become bipedal and as diet quality starts to get better. And then once you get to, I mentioned Homo erectus before, you've got a hominin that's kind of got the same gut size as us. Brain size is still growing. So there's still a bit of flux within that. Now, why would the gut size shrink and the brain size grow? You've got to have selection pressure on the brain size to say, "This is something that we need to grow," and then there's got to be a change somewhere to release the energy to allow brain growth. So one of the ideas, and it's called the expensive tissue hypothesis, it's still, I think, quite an elegant one even though it's about thirty years old, by Aiello and Wheeler. What they kind of say then is while the trade-off in us is that our guts shrank and our brains grew, and our guts shrank because our diet quality probably started to change. So when we start to have access to proteins, in the original idea, proteins and marrow and things, and we were regularly starting to eat those more high-quality input foods but also using stone tools to cut them up and things like that. So we're not kind of ripping into it and holding the leg to our mouths and chomping down. We are cutting up and eating the strips. It means there's less energy to process the food, but it's a higher quality food, and therefore, whatever's selecting for brain growth, you're releasing energy there. And our stomachs don't need to be as big because the food that we're eating is a bit more high quality.

Jonathan: And James, when you say higher quality, do you mean like more calories? Yeah. Just to understand, 'cause I think that might be a different way than perhaps Frederica might think about higher quality.

James: Yes. Okay,

Jonathan: yes.

James: It's a good point. So higher quality in terms of like protein content and that access to protein. But interestingly, a refinement of the idea is that it's not just about protein, but about fats. Fat gives you more energy than protein does. When you get access to that more regularly and something selecting for brain growth, which we think is probably about social group size and social interactions and the complexity of keeping track of what everybody's doing, then the energy from these kind of higher quality foods, 'cause they give you more energy than, say, grasses or sedges or things like that that you might eat as a primate, that then starts to kind of start or coalesce through a matter of happenstance really to lead to the guts shrinking and the brains growing and ultimately to where we end up today. Can I

Federica: ask a clarifying question? You've mentioned- Yeah ... the gut shrinking- Yes ... and the stomach shrinking. The stomach shrank because less digestion needed to happen in the stomach, but did the actual gut length also shrink in terms of small intestine and large intestine? 'Cause obviously that's where our gut microbiome resides. Right. So I'm really interested in understanding about that.

James: From my archeological later, my interchangeability is that they would all shrink together. All,

Federica: okay.

James: But I'm happy to be proved wrong if someone wants to correct me

Federica: on that. No, it's just so, it's just interesting to learn we got more efficient- Yeah at absorbing nutrients from the food we were eating-

James: Yes ...

Federica: with this change in diet, thanks to our tools- Yeah ... and this ability to maybe hunt socially and things like that.

James: And also cooking.

Federica: Yeah.

James: How do we understand the role of fire, and what does that tell us about what our ancestors were eating? Yeah, so it's very interesting about fire 'cause we tend to think, oh, once fire is invented, it's there forever, and everyone knows how to use fire, and it's just there. But actually what we see with fire is that it probably comes in three or four times, or more. You know, it's constantly being rediscovered and maintained. It's not like a kind of a single thing that occurs, and then everybody does it. There's lots of interesting thoughts about the origins of how we might have understood or come to see that there was a benefit to cooking something. And there's been really interesting work done looking at wild forest fires and looking at what animals do after a forest fire. So for example, if there's a forest fire, you can see that chimpanzees and birds of prey and things can then go follow behind the fire, in effect, find charred carcasses of deer or whatever that got caught, and exploit that material. So that might kind of be sort of a spark moment that cooking something or certainly burning it makes it kind of easier to digest and break down. But fire's really important because it does kind of in effect, kind of almost from my understanding, and feel free to correct me, Federica, is it kind of It almost, it breaks it all down before it gets to your stomach, so then you don't need to expend so much energy breaking the food down, so you can take that energy and shovel it into our brain growth.

Federica: Yeah, it is a form of pre-digestion when we cook food, and it makes different nutrients available in different ways. To your point, Jonathan, it also makes carbohydrates more efficient to absorb. So it works for proteins, it works for carbohydrates. It changes the way certain micronutrients are absorbed as well. So it, yeah, it changes the way we can use the food, and it does make it easier to access the energy and some of the nutrients.

Jonathan: What is our evidence for what we were cooking? Yeah. Like, to what extent was it, like, all the hunks of meat that you're describing? Yeah. To what extent was it actually, you know, sort of- Other plant material ... the starches and plants that Federica's talking about?

James: So there's some really amazing sites where we have preserved hearths. So you can see from a site called GBY, Gesher Benot Ya'aqov, in the Near East where they've got sort of burnt seeds of plants. And there are other sites in Europe and things that also have these burnt plant remains that have preserved within the hearth ashes. So you can see that these plant materials are also being cooked by the fire. But the other thing with fire is it's not just about cooking. And as with all of these kind of technologies with the past, there are multiple benefits. So another benefit of fire is that it extends the daylight hours. So what that means is you can go out during the day foraging, and you can gather all your stuff, but you don't have to process them straight away or eat them straight away in the way that other day-based primates might. You can take them back to your base camp or your camp, then you can sit around the fire, you can process the foods there, cook them, but you can also do your social interactions at that point. So that strengthens group cohesion, extends it into the nighttime so you're not just stuck to dawn to dusk living in that respect, 'cause we're not nocturnal in that way. It also provides warmth and then possibly protection from other kind of night predators. But if we look at ethnography work, so I'm talking about looking at indigenous communities now who live in traditional ways, still today, and what we can see from their life, their sort of daily journey, is that they only have to do that kind of food resource gathering about four to five hours a day. Then there's the sort of leisure time packed around that, and then the kind of cooking and the processing. So it's actually a much more relaxed way of life.

Federica: Historically, we used to spend a lot of time together-

James: Yes ...

Federica: hunting, foraging mostly, gathering, and then coming back and preparing together, sharing our meals together. It's such an important part of why food is so fundamental- Absolutely ... for humans, right?

James: Yeah.

Federica: So maybe that's something that we can carry forward to now, and we've moved really far away from it. If you think about drinking your lunch at your desk, I mean, how far removed is that from how we evolved? That's what I think is stark.

James: It's the social driver of that kind of social cohesion as a group, and you can see even within the archeological record on some of these hearths. So there's a site in England called Beeches Pit, which is some of the oldest fire hearths in the UK, about 400, 450,000 years ago.

Jonathan: 450,000 years ago- Yeah ... we found, like, a fire?

James: It's a site that they return to, but what you can see in one of these layers is that you've got two or three hearths, and then you've got someone who's kind of working a stone artifact at one hearth, and then they've obviously got up and walked across to another one and done a bit more working there. So they're moving around the hearths. And speaking to your point, Frederica, it is about that kind of social engagement with each other, working, sitting around. And we can track that on some of these sites where you can see these bits. And the reason why we know is that these flakes have fallen off into the hearth. They've become burnt by the fire, so they give a particular signature, and then we kind of refit them across the locations of these archeological sites. So you can actually at some points track what someone was doing in a kind of 10-minute window- ... half a million years ago.

Federica: It reminds me of, like, you know, when you see nonnas in Italy, and they're all sort of posturing- Yeah in the kitchen together. And one goes over there and stirs the sauce, and then the other one goes off to check on the bread, and then the other one's slicing the cheese. Like, that's what I'm picturing- Yeah ... now. There's such elements of that in when you look at the longest living populations- and populations that have the healthiest diets. There are elements of that still persisting today. I think a lot of people connect with that as a really essential experience of what it means to be in a human society and in a connected household.

Jonathan: Now, last thing that I do wanna touch on in terms of this, like, real Paleolithic period, I understand that you've discovered that there was cannibalism during the Paleolithic. Is that right?

James: Well, I appreciate the accolade. I didn't discover it, but what I did do is try and work out what the calorie value of different parts of the human body were. And that sounds quite gruesome, and it wasn't any kind of primary interest on my behalf. It was more just about trying to understand why we would cannibalize. We say this word and it conjures up horrible, gruesome images, but there's a whole range of reasons why we might do that. But the only reason why we have that range of motivation today is because it's evident around us in the world, and we can kind of access that. But the further time you go, the harder it is to understand why someone might do something, 'cause thoughts don't preserve. We only have fossil remains. So for the Paleolithic cannibalism, you know, we can track definite episodes of cannibalism back almost a million years in time. And cannibalism is a small signature in the fossil record, but it's very persistent. So that kinda suggests that this probably is quite a common practice amongst our human ancestors. Often it's just kinda thought, well, it's just because they didn't have anything else to eat, and it was just part of a dietary expansion, or it was ritual. So I just thought, well, if I could compare our calorie value to a mammoth, for example, or a horse, which we know that were also being hunted and had these cut marks on them in the same layers, so they were accessing these other animals, maybe that sheds a light on kind of why we might do that. And I guess in a bit of an underwhelming way, I found that we have probably the right amount of calories for an animal of our size. We're just not very big animals compared to horses or anything else. So, you know, a horse will give about 200,000 calories worth from their muscle, and we will give about sort of 30-odd thousand from the muscle. Of course, there are other bits that we can consume, but if we just take the muscle, the flesh. So it didn't make sense to me then for it to just be about food because they were getting much bigger sources of calorie from the animals, let alone the plants and things that we've spoken about already.

Jonathan: And James, are you saying that it seems to have been quite common in the Paleolithic period for our ancestors to eat other human beings?

James: I think if not common, certainly persistent. And that's because we have a small number of fossil remains of all the people who have ever lived, and even within that small number of fossil remains, you know, we have a consistent signature of where cut marks are being found on human and hominin bones to show that they have been butchered. And the cut marks are there, I should clarify, they are positioned at butchery points. So they are about cutting the flesh to butcher.

Jonathan: I'm already thinking that we

James: don't necessarily want to copy everything that- Not everything, no ... our Paleolithic

Jonathan: ancestors ate. Is that fair to say, James?

James: I think that's absolutely fair to say, yeah. Yeah, not everything, but some things are, we have some good advice from them.

Jonathan: I'd love to turn to this modern paleo diet. Yeah. What is the modern paleo diet? And, you know, why has it generated so much interest and for so many people seem very appealing?

Federica: So it started with a book in the 1970s called, like, The Caveman Diet, I believe. And it started gaining some traction, but it blew up in popularity in 2002 with a book called The Paleo Diet, and it became super popular. Lots of people adopted it, and especially sort of the CrossFit, very health-conscious community started to adopt it. And what it does is it tries to point to history as having a magical diet that used to really suit us as a species and that we should return to that. So the idea of the paleo diet is the modern food environment is making us sick, and I think, you know, we can all agree there that they got that right. And actually, they got that right quite a long time ago. 2002, to be pointing to added sugars and UPFs as an issue was very ahead of the time. But they got the right problem, but the wrong solution, so Which is also quite a human characteristic.

Jonathan: I was going to say- ... that sounds incredibly human, doesn't it? Yeah. God.

Federica: And so they were like, "Okay, there's really an issue with these added sugars. There's an issue with these industrially-created food products, and the answer is a paleo diet." But as we've learnt, the paleo diet that's described in the book is actually not reflective of what the paleo diet actually was. So the modern paleo diet essentially points to a diet that is mostly fish, meat, fruits, nuts, and seeds, but completely eliminates dairy, whole grains, and legumes. Also, no alcohol, no added sugar.

Jonathan: What are the things in there that actually seem good to you-

Federica: Yeah ...

Jonathan: as you look at it?

Federica: So for me, this moving towards whole foods, reducing our reliance on ready meals, packaged foods, industrially processed foods, UPFs essentially. Reducing that is obviously a good step. The other thing is this removal of alcohol, for many people, will be a benefit to their health, and the avoidance of added sugars. So we know that there is a crisis with the amount of added sugars in our diet with things like sweetened sodas and pastries and biscuits and things like that. So what I do quite like about the paleo diet is it is one of the only diets of this branch of diets... 'Cause paleo has sort of evolved into keto and carnivore now, but the paleo diet still retained fruits as an essential part of our diet. So it understands the difference between added sugar and naturally occurring sugars, which is important.

James: And I think something that's quite interesting about fruits is that certainly primates and us seem to have evolved for a real affinity for vitamin C, which comes through from the fresh fruits. So yeah.

Jonathan: The thing I think of first with, like, the paleo diet is eating loads and loads of meat. Interestingly, you said meat and fish. So, you know, in that diet where you can have fish, meat, fruits, and seeds, clearly you're gonna get the vast majority of your calories from, like, this meat and fish. Were we really eating as much meat and fish as that in the Paleolithic?

James: Certainly, it was in the mix. So we definitely have large shell middens where we were exploiting the marine environment. Not so much, you know, necessarily fish in the way that we consume fish now because that requires deep water fishing and things. So these would've been things that are around coastal environments, so shellfish. There's also evidence of things like dolphin being consumed, seal and things like that. So definitely a marine diet within that. And that's both within our species, Homo sapiens. We can see that from sites in South Africa and other coastal ones, but Neanderthals as well were also exploiting that marine environment.

Federica: What I picked up from what you said earlier is that it was very seasonal and dependent on where you were. Yes. Yeah. So not all Paleolithic humans were eating meat and fish, actually.

James: Correct, all the time. Exactly. It's only if they were situated in those localities that were allowing them to then exploit those ecological zones. And they were quite mobile generally as a whole population, kind of lots of movement around, so...

Jonathan: Because I think part of the paleo, and I think this is part of the appeal, is, like, actually our ancestors were a bit like a tiger or a lion. Right. Yes. Basically, they ate an almost entirely meat diet. Right. How accurate is that?

James: Well, it's difficult to quantify the amounts that they were doing. But from all the evidence that we've kind of discussed already, we can see that it wasn't just meat, and it wasn't just fish. They were parts of the diet, but there were all of these other components that were sitting there either together or at different times of the season or the kind of the day, depending on how successful they may have been at hunting or foraging. I

Federica: think it's fair to say, Jonathan, the paleo diet recommends a really high protein intake. It's often in excess of two grams per kilogram of body weight, which means eating a lot of meat or fish every day at every meal. And from what you're saying, James, it sounds like our ancestors may have been lucky to catch a horse and eat it, but that would not have been an every meal occasion.

Jonathan: My takeaway from this is that there's a lot of variety in the amounts of meat that our ancestors ate. But it sounds like there's not many of them who are going to be eating this, like, 80%-plus of all their calories are coming from red meat. Am I getting that right, James? Yeah,

James: I, that's certainly how I would read it.

Jonathan: And interestingly, within that, that what they ate as meat is probably different from a domestic cow, and I think I'd like to come back to that, but before we do, can we talk a bit more about the no grains or dairy?

Federica: Yes.

Jonathan: Because clearly if you can't eat any of those, you are literally on, like, fruits and seeds, and it's a pretty limited amount of your meal that you're gonna get from that. Why did they think that was the right conclusion for paleo?

Federica: So the author of this book and the paleo community believe that whole grains, legumes, and dairy are a modern phenomenon to humans. So when we started farming practices, we started to drink milk, keep cows, grow grains, and grow legumes for consumption. There's also misinformation around pulses in this community that some of their contents, like lectins, are poisonous for humans and so shouldn't be consumed. So there's lots of reasons why they've excluded it from the diet, but actually, what's interesting is that, A, whole grains were consumed millions of years ago, so that's wrong. The dairy one is interesting 'cause we've evolved lactase persistence, so the reason we're able to digest dairy as adults, not all communities, not all humans can do this. It depends where you're from. So if you're Southeast Asia, you may not have lactase persistence, actually, for example. But a lot of humans now continue to make the enzyme to break lactose down in milk so we can make the most of it as a food 'cause it's nutrient dense. So we've actually, many of us have evolved to have dairy in our diet, hilariously. And legumes, I wanna take this head on. It does contain phytates and lectins, but when you cook your legumes, which we all should be doing, and when you soak them and cook them properly, they are all deactivated. So this link of lectins and chronic health conditions is just made up. It doesn't exist. There is a risk of acute vomiting and diarrhea if you don't cook your pulses. But that's it. And Federica,

Jonathan: for people who aren't at all familiar with this- Yeah ... and you're talking about legumes and pulses.

Federica: Beans, lentils, chickpeas, green peas, soya beans. These are the wonderful world of pulses and legumes. And if you buy them tinned or jarred, they're already cooked for you, so you don't even need to worry about it

Jonathan: And so James, if we go back to like what the latest- Yeah ... archaeology is showing us, and I think you've already told us, well, actually, our ancestors cooked food. That was a really important part.

James: Yeah.

Jonathan: Were there no whole grains or dairies or beans or any of these sorts of things in the past?

James: I mean, I certainly wouldn't rule anything out around that because absence of evidence is not evidence of absence in that respect. But what we can see, as Friedrich said, you know, whole grains were certainly consumed. Neanderthals seem to have been eating whole grains at least sort of 60-odd thousand years ago. We also know our hominin ancestors have been eating things like sedges. What is a sedge?

Federica: Sweet potato or

James: a- Sweet potato ... yeah. Yeah ... something like that. Yeah. So that would've been consumed also, and we can see that in Australopith and Paranthropine diets three million years ago. So these things would've been part of that process. Dairy's interesting because that does seem to come into our kind of more regular diet consumption post 10,000 years ago, but we have evolved to consume the dairy once we've kind of entered Neolithic kind of farming period after the Paleolithic. We know that wild sheep, mouflon, were hunted and eaten for many hundreds of thousands of years. So it's natural if you're in the same environment as these animals, you're not going to escape an opportunity probably to try something like that and then kind of take advantage of it.

Federica: Yeah, so I think that the modern paleo diet is based on shaky foundations of a misconception of the history that it's supposed to be representing. But it resonates really well with people who want a simple solution of, okay, with all of our problems come from this issue of the modern food environment, and the solution that's been presented with the paleo diet is, "Don't eat it unless a caveman would eat it." And as we've discussed- ... our ideas of what that means are very much shaped by the story that we were told about cavemen, which is actually incorrect. So, and what we've done now is we've got this real dietary trend that is extremely exclusive of some of the foods that are best known to be supportive of our health. And so this is where for me, it's frustrating because it's very popular as a diet, but actually, it excludes the food groups that we all need more of and demonizes them in a way that isn't scientifically rigorous or historically relevant.

Jonathan: Would you recommend the paleo diet as a healthy diet for someone to follow?

Federica: No, not for the long term. However, I know many people find the paleo diet helpful to start their health journey. The positives of the paleo diet, of reducing ultra-processed foods, reducing excess sugar, removing alcohol from daily diet, those are good first steps to start changing your diet. Another thing that many people report on the paleo diet is that they have to reconnect with cooking at home, because there is such a focus on whole foods that you have to kind of do it. In the long run, keeping to this kind of dietary pattern is excluding the major food groups, specifically whole grains and legumes, that are essential for our health, specifically through the action they have on our gut microbiome. And when we remove these, we're removing some of the polyphenols, the fibres, the resistant starches that are essential for gut microbiome composition and function. And there is actually quite a lot of data on the paleo diet, Jonathan, and some of the RCTs and the meta-analysis, so some of the trials that have been run, show that people who stay on the paleo diet for a long time start to express some metabolites from their gut microbiome, some byproducts that are actually harmful, such as TMAO, which is actually associated with heart disease, basically. So staying on this diet for a long time can be more harmful. There's one interesting study in post-menopausal women with obesity, and at six months the paleo diet was better for them compared to standard American diet. But by 24 months, they'd returned back to baseline. So it's not a sustainable long-term intervention. And I think it's really important to point out that it has negative impact on your gut microbiome and can have negative impacts on your long-term heart health and type 2 diabetes. We don't want to increase that risk. What I'm struck by, Jonathan, is this idea that actually every community had a different diet at different times of the year in different parts of the world. So if anything, a true paleo diet would mean looking to what's available to you locally, eating seasonally-

James: Yeah ...

Federica: and having the most varied diet possible, which is what our physiology makes us so good at.

James: Right.

Federica: I believe that we used to have a much more varied diet up to over 10,000 years ago. We used to eat dozens more types of plants, didn't we? Yeah.

James: Yeah, absolutely.

Federica: So returning to a more variety of food, a wider variety, is where we should be heading, not restricting back to just saying red meat, fish, fruits, nuts and seeds.

Jonathan: If you were gonna design like a proper modern paleo diet, what else would you be advising people to do?

Federica: It would definitely be centered on variety, seasonality, preparing food from whole foods together, and sharing that food in your group. One thing I would definitely take away from this episode is that whole grains and legumes are an essential part of a healthy diet. And we see in modern data of dietary patterns that people who eat more whole grains, 90 grams of whole grains a day can reduce your risk of dying from cardiovascular disease by up to 25%. We now eat a few hundred types of plants. We used to eat thousands. Try to get 30 plants every week. Introduce new things like spices and herbs, nuts and seeds, whole grains, pulses, legumes, like really go for it. See what you can add to your shopping basket, or go to your farmer's market, or grow them in your garden if you have one. And get to know the diversity of plants that are accessible to us. Whole fruits are fantastic as well, so making sure that you have those in your diet. The biggest trap I see with the paleo diet is this increase in consumption of red meat and processed meat because unfortunately they're conflated often. And whilst fresh red meat occasionally is not a problem for most people, I think it's absolutely can be part of a healthy diet. It's not an essential part of the diet, but it can be healthy. Processed meat has measurable negative effects on risks of cancers. And, you know, with colorectal cancer, Jonathan, it's a massive increase in risk, up to 70% with every portion of processed meat you have per day.

Jonathan: What's a processed meat?

Federica: Bacon, sausages, ham are the ones that people would recognise the most. But now some food manufacturers are masking processed meats as health foods, making things like deer meat jerky, and it's like that's still a processed meat. Another thing I picked up from what you said, James, is going back to eating animals that are more sustainable and maybe are less intensively farmed, like venison, could be a good thing for us to do more of. So here, you know, globally, there's different breeds, different animals that are more sustainable because they have to be culled. In the UK, venison is certainly one of them. So if you do have red meat in your diet, explore how you can make that better for you and better for the environment as well.

Jonathan: What did the meat eating look like? Like, today, we're very focused on, like, as you described before, like, eating the muscles. You know, I wouldn't eat any other part of an animal. What would our ancestors have, in fact, been- Right ... eating?

James: I think they'd have eaten the whole lot. There wouldn't have been anything wasted because it takes a lot of effort to hunt a big animal or a small animal or any animal really in that respect. So there wouldn't have been anything wasted at all. What we can see is that they were selecting what animals to kill, so they weren't going for the young or the elderly or the sick. There's a lot of evidence that Neanderthals and others were hunting prime age adults, so you know, peak kind of fitness, the strongest to get the best quality, I guess, out of it, and the most bulk. So they would have eaten everything, and there was a lot of long bone breakage and a lot of interest against the marrow. So they were really stripping it down and consuming it all.

Federica: And that's something we can bring today. Like, nose to tail eating is- Yeah ... a much more effective way to use the animals that we do kill. So I think there's a lot of value to that.

James: Yeah.

Federica: And you might not like liver, but it's extremely nutrient dense. Unfortunately, though it's nutrient dense, in our modern environment, it's also where all the toxins accumulate. So you have very high levels of B12, iron, vitamin A. Vitamin A is actually very, very high, so regular consumption can lead to vitamin A poisoning. But it also is where PFAS, forever chemicals, accumulate in the liver. It's where a lot of the antibiotics are used. So the things that we now use to grow our animals and that are in our environment also accumulate in the liver, so we have to weigh that risk.

Jonathan: And James, I often hear, particularly in the US, people say, "Well, I only eat grass-fed beef, and so that's, like, the same as the sort of, you know, animals that I was evolved to eat." Right. Is that true?

James: Depends on the animal, because we ate lots of animals historically. So some of those would be open grass eaters like horse, wild cow, and so on. Others would be sort of forest dwelling and so on. But I think the difference within our modern environment, and Frederick, you mentioned sort of the forever chemicals, and the thing that sprang to my mind are microplastics and things like that. Every... You know, that we can see the impact that we've had on the world just over this kind of last, what, 60, 70-year period where we've invented plastics. That is now in our food chain.

Federica: Yeah.

James: So in effect, it's all kind of curated in a human way in terms of how we control the environment and how we've impacted it.

Federica: So they're very different to what we would have hunted down.

James: Very different.

Federica: I have to say grass-fed beef does have a slightly different nutrient profile, and often you'll hear people who talk about grass-fed beef being like, "Well, it has omega-3s." And it does have some from grass, but it's minimal compared to what you get from, like, a walnut. It's this... It's also omega-3 ALAs, so it's the same as a walnut. It is not DHA and EPA, which is what you get from fish, which is what is essential to us. So there's a bit of, like, marketing around grass-fed beef. I'm happy because the cows get to go outside. But essentially, the nutrient differences are pretty minor.

Jonathan: One thing I'm aware we didn't talk about at all is, like, fasting and, like, the time when people are eating. And that's obviously been a really big interest. It's something that there's been quite a lot of research that ZOE's been involved with as well. Can we infer anything about, like, when our ancestors ate or how often, or is this not

James: something that we can?

Jonathan: no.

James: It's the... I wish we could, but the time depth is so great that we can't get that kind of daily resolution from the archeological record.

Federica: For me, Jonathan, it's this idea, I think we've heard how much our ancestors had to work to get enough food, and then how long it took them to come back and prepare the food. Right. So I imagine that there was periods where there was more food available, and periods where they were living off of pre-prepared-

James: Definitely,

Federica: yeah ... seeds and grains that they had ready for them. And do you see that from modern societies today that's still?

James: Yes, I think that's still a reasonable model. And the other thing, of course, is sort of some of the preservation that you can do with some of the proteins that are made through smoking meats and things like that.

Federica: We can't always map what we know from modern science back to history. But what we do know from our own ZOE study on fasting, and from lots of other studies that have taken place since, is that people do better if they have a bit of a break from eating. And specifically, just having an overnight fast- that's between 12 and 14 hours seems to support our natural circadian rhythms.

James: Right.

Federica: And thinking about cave-dwelling people or paleolithic humans, you know, I guess, or hominoids, if that's the correct term, you know, they would have slept at night- Yes and they would have-

James: Definitely ...

Federica: eaten in the day. Yeah. So it kind... And from an evolutionary point of view, it makes sense that we benefit from having this overnight fast. But what I'm also getting from you, James, is that there was just a lot of variety, so that I think we're adaptable and we shouldn't be too scared of having a day where we eat a bit less, and then another day where we eat a bit more, and actually just listen to our bodies and go with what we're doing, 'cause our bodies are pretty clever at telling us when it needs more energy or not

Jonathan: Federica, one of the things you said that was good about this modern paleo diet is it got people to basically reduce or cut out their intake of ultra-processed foods. Yeah. If someone is interested in trying to achieve that without becoming sort of obsessive or overly restrictive- Yeah ... and they're not gonna do the modern paleo diet, where should they start?

Federica: Become aware of the foods in your kitchen that are ultra-processed. Awareness is key. But then start to introduce foods that we need to eat more of, and build meals around those. Cooking is essential to this, so get comfortable with the cooking skills you have. You don't have to be a Cordon Bleu chef, but just start somewhere. And as you do that, the UPF products will no longer have such a place in your life.

Jonathan: I love it. And James, last question for you. You know, spending your life studying Paleolithic people, is there anything that you've learned from this that guides your lifestyle today?

James: In terms of the diet, I would always try and go local- Yeah ... seasonal, and as always, everything kind of in moderation Amazing. I'm gonna try and

Jonathan: do a quick summary, and we've covered a lot of things. Please correct me, both of you, if I get any of this wrong. So first thing that comes to my mind is that we think about the whole idea of this modern paleo is our ancestors got everything right. But actually, almost all of our ancestors died by the time they were 40, and they were in pretty tough shape. So we shouldn't assume that everything that they were doing with their lifestyle was perfect. That said, we now know a lot more than we did even 20 years ago, which is amazing. Yeah. And one thing that I'm struck by is this idea that our bodies have evolved a lot from, like, our primate ancestors. And one of the big things is that they evolved to be able to eat a very varied diet. So unlike all of these other, you know, chimps and gorillas, like we can eat all these different things. And one of the things that we did is we actually our bodies evolved because we discovered fire. And so suddenly we, like, we now had this cooking, so then, like, our gut can shrink, and suddenly there's all these different foods that we can get. You know, it's almost we can get the best of being like a carnivore and a herbivore. So you can suddenly eat all of this meat, and you can even cook it to digest it better. But interesting you were saying, like, our ancestors were also eating things like tubers, like sweet potatoes. Like, no animal could eat that unless it's, like, sitting in their stomach for days. So that's sort of magical and helps explain, I guess, a lot of this variety of what we do. We can actually understand a lot of the things that we ate, and so we know that our ancestors absolutely did eat meat. We also know that they ate plants because we've been able to find that in our ancestors' teeth. And we also know that our ancestors spent a lot of time, like, preparing food and spending time around the campfire. Back to Federica's love for this idea that, like, one of the things that's so important is actually sort of to be with other people, preparing food and eating food. And the sorts of foods that our ancestors ate are a whole bunch of the foods that this modern paleo diet said that we mustn't eat. So we know they ate whole grains. We know that they ate, like, root tubers, like sweet potatoes. Dairy is much more recent. Yeah. So we have only had that for the last 10,000 years. But interestingly, it was so important for ancestors that, like a lot of human populations have evolved the ability to actually eat it as adults. And maybe the last thing on the past is that when we think about our meat and what our ancestors were eating, we shouldn't think that these are the same. Like, eating like a venison that is running around- Yeah ... you know, in the wild is much closer than, like, a cow that just sits in a field, never moves, and is sort of immensely fatty, even if it's grass-fed. Then I think we came onto the modern paleo diet, and I think my takeaway was there are some good things. It gets you to, like, basically stop all the ultra-processed food, all the added sugar. You're taking out alcohol. Like, those things will make you feel much better fast, forces you to start cooking. But it has all of this restriction. It's stopping you eating all of these things like whole grains and legumes, which Federica is like, "These are the best things- Yeah, literally ... for your microbiome and your health." For your

Federica: health, yeah.

Jonathan: And so then finally, so what should you do? And Federica, I think what I took away was 30 plants a week, which gives you all of these whole grains and the whole foods that you want. To try and prepare from scratch as much as possible. To eat seasonally, because that's gonna give you this variety, not just 30 plants a week, but therefore many more plants- Yeah ... over the year. As varied a diet as possible. Try and capture the social aspect of the Paleolithic, so spending time with your group, not the eating- Yeah not the cannibalism. But the spending time with a group. And definitely no processed meats. Like, our ancestors did not eat any processed meat, so this bacon, you know, the venison jerky, like, this stuff is really bad. Take it out, and instead think about, "How am I getting all of these whole grains, these legumes, the beans and the chickpeas and all the rest of it?" Because they can make you live not just till 40, but hopefully to-

Federica: 120 ...

Jonathan: 120. Yeah.