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  • Thank you, it's a pleasure to be here.

  • I'm an archaeological scientist

  • and I study the health and dietary histories of ancient peoples

  • using bone biochemistry and ancient DNA.

  • I'm here because I want to talk to you about the Paleo Diet.

  • It's one of America's fastest growing diet fads.

  • The main idea behind it is that the key to longevity and optimal health

  • is to abandon our modern agricultural diets,

  • which make us ill,

  • and move far back in time to our Palaeolithic ancestors,

  • more than 10,000 years ago, and eat like them.

  • Now, I'm really interested in this idea

  • because it purports to put archaeology in action,

  • to take information we know about the past

  • and use it in the present to help us today.

  • Now, this idea was really started in the 1970s

  • with this book, "The Stone Age Diet."

  • It's diversified since then into several variants,

  • including the Paleo Diet, the Primal Blueprint,

  • the New Evolution Diet, and Neanderthin,

  • and most of the language of these diets makes references to anthropology,

  • nutrition science, and evolutionary medicine.

  • The diet does seem primarily targeted at men,

  • so if you look at advertisements and descriptions,

  • they have virile, cavemen-like images,

  • things like "live primal," lots of red meat.

  • And basically, the idea behind it can be broken down into four parts.

  • One is that our agricultural diets today make us chronically ill,

  • that they are out of sync with our biology.

  • And two, that we need to abandon these agricultural diets

  • that started during the agricultural period,

  • and move back in time to the Palaeolithic

  • and eat more like our ancestors over 10,000 years ago.

  • Third, that we know what these diets were like,

  • and what they were like was they had a lot of meat, they were mainly meat based.

  • That was supplemented with vegetables and fruits and some nuts and oils,

  • but it definitely did not contain grains or legumes or dairy.

  • And fourth, that if we emulate this ancient diet,

  • it will improve our health and make us live longer.

  • So what I want to talk to you about today is that this version of the Paleo Diet

  • that's promoted in popular books, on TV, on self-help websites

  • and in the overwhelming majority of press has no basis in archaeological reality.

  • So, thank you!

  • (Laughter)

  • No, I'm not going to end there; I will explain.

  • So what I want to do as an archaeologist is go through this,

  • do a bit of myth-busting

  • of some of these foundational archaeological concepts

  • upon which it's based,

  • and then I want to talk to you about what we really do know

  • from the archaeological record

  • and from scientific studies about what Palaeolithic people did eat.

  • So, myth one is that humans are evolved to eat meat

  • and that Palaeolithic peoples consumed large quantities of meat.

  • Humans have no known anatomical, physiological,

  • or genetic adaptations to meat consumption.

  • Quite the opposite, we have many adaptations to plant consumption.

  • Take, for example, vitamin C.

  • Carnivores can make their own vitamin C, because vitamin C is found in plants.

  • If you don't eat plants, you need to make it yourself.

  • We can't make it, we have to consume it from plants.

  • We have a longer digestive tract than carnivores.

  • That's because our food needs to stay in our bodies longer,

  • so we have more time to digest plant matter.

  • We need more surface area, we need more microbes.

  • We have generalist dentition,

  • so we have big molars that are there to shred fibrous plant tissue.

  • We do not have carnassials,

  • which are the specialised teeth that carnivores have to shred meat,

  • and we do actually have some genetic mutations in some populations

  • that are adaptive to animal consumption, but it's to milk, not meat,

  • and these arose in certain populations during agricultural periods

  • primarily in Europe and Africa.

  • I call this "The Meat Myth."

  • The idea behind it is that we should eat all this red meat,

  • but that's just really not true.

  • The meats on this plate of meat here

  • are from fattened cattle, these are domestic animals.

  • Anything a Palaeolithic person would have eaten

  • would have probably been very lean, probably small,

  • and they wouldn't really have eaten that much meat.

  • Of course there's also bone marrow and organs,

  • these would have been very important.

  • We see evidence of harvesting of bone marrow in faunal assembles

  • where you see characteristic cutting open of the bones,

  • like you see here, for marrow extraction.

  • Now sure, people did eat meat,

  • and especially in the Arctic

  • and areas with long periods where plants were not available,

  • they would have eaten a lot of meat.

  • But people that lived in more temperate or tropical regions

  • would have had a very large plant portion of their diet.

  • So where does this Meat Myth come from?

  • There's really two places,

  • and one is the inherent bias in the archaeological record.

  • Bone is 80% mineral by weight, it's going to preserve better and longer

  • over thousands of years than delicate plant remains.

  • But the other issue comes from some early bone biochemistry studies

  • that were performed on Neanderthals and early people.

  • This bone biochemistry study

  • is based on something called nitrogen stable isotope analysis.

  • It's complicated, but I'm going to try and break it down.

  • The basic idea is that you are what you eat, and so we -

  • there's nitrogen-15 and nitrogen-14, heavy and light versions of nitrogen -

  • and we consume this nitrogen in our food.

  • But there's one important difference,

  • and that is, with each step that you go up the trophic hierarchy,

  • the amount of the heavier isotope increases.

  • So if you measure the amount of heavy isotope in the bone,

  • you can infer where that individual was on a food chain.

  • This is an example of a generalized isotopic model.

  • I've plotted where plants generally fall, and above them are the herbivores,

  • and then above them, the carnivores.

  • But one of the problems is that not all ecosystems conform to this model.

  • There's a lot of regional variability, so if you don't understand the region,

  • you can come to erroneous conclusions. I'll give you some examples:

  • we can take East Africa; if we measure animals and ancient humans,

  • in East Africa, we see some very strange patterns.

  • First of all, how can a human be higher than a lion?

  • Lions only eat other animals. And then, how is this herbivore above a lion?

  • Well, it turns out that the food that you eat is not

  • is not the only contributor to these isotopic values.

  • and that aridity can also have an impact.

  • So what we're likely seeing here is differences in water access.

  • So let's move out of the savannah and move into the tropical areas.

  • Let's look at the ancient Maya; again we see something anomalous.

  • We see the ancient Maya lining up with jaguars.

  • Now, we know the ancient Maya had a diet heavily reliant on corn.

  • So what's happening here?

  • We don't exactly know, but we think this may have to do with

  • the way they performed agriculture and how they fertilised their crops.

  • Now let's go to the Pleistocene.

  • We see some really interesting patterns here too.

  • We see reindeer plotting very low, in the range of plants.

  • We see wolves plotting normally where you would see herbivores,

  • and we see mammoths spanning all three levels,

  • at once plants, herbivores and carnivores.

  • So what we think is happening here

  • is that in very cold climates, animals eat unusual things.

  • and in this case what we think is happening

  • is these mammoths are eating lichens and bark

  • and that's giving them very strange values.

  • So if we now go to humans, ancient humans, Palaeolithic humans, and Neanderthals,

  • we see that they plot in the same isotopic space as wolves and hyenas.

  • Now that's true, but as I've shown, if you don't have good control

  • over the regional isotopic ecology, you can come to an erroneous conclusion,

  • and I think it's premature to say

  • this is very strong evidence of meat consumption,

  • given how very little we really know about the Palaeolithic ecosystems.

  • So, myth two is that Palaeolithic peoples did not eat whole grains or legumes.

  • Now, we have stone tool evidence from at least 30,000 years ago -

  • that's 20,000 years before the invention of agriculture -

  • of people using stone tools

  • that look like mortars and pestles to grind up seeds and grain.

  • More recently we've been developing techniques

  • where we can actually measure this thing called "dental calculus."

  • It's very interesting: it's fossilized dental plaque.

  • We can go in the individual mouths of people, pull out that plaque

  • and recover microfossils of plants and other remains.

  • My team is working on developing methods to extract DNA and proteins,

  • and other research groups are focussing on these microfossils

  • like starch grains, pollen and phytoliths.

  • Now, we're still in early days here,

  • but even with the limited research we have,

  • we can say that there is an abundance of plant remains

  • inside the dental calculus of Paleolithic peoples.

  • And these things include grains, including barley.

  • We're finding barley inside Neanderthal teeth, or inside the plaque.

  • We also have legumes and tubers.

  • So, myth three is that Paleo Diet foods, in the fad diet,

  • are what our Palaeolithic ancestors ate.

  • That's just not true.

  • Every single food that's pictured in these advertisements

  • are all domesticated foods, products of farming, of agriculture.

  • They're from the Neolithic transition.

  • Let's give an example - bananas.

  • Bananas are the ultimate farmer's food.

  • They can't reproduce in the wild anymore.

  • We've bred out their ability to make seeds.

  • So every banana you've ever eaten

  • is a genetic clone of every other banana, grown from cuttings.

  • They're definitely a farmer's food.

  • If you were to eat a wild banana, it is so full of seeds

  • that I bet many people in this room wouldn't even recognize it as edible.

  • Let's take salads, that seems like a really great Paleo Diet food.

  • Except that we've radically changed the ingredients to suit our needs.

  • So, wild lettuces contain a great deal of latex,

  • which is indigestible and irritates our gastrointestinal system.

  • It's bitter, the leaves are tough.

  • We've domesticated them to be softer, to produce bigger leaves,

  • to remove the latex and the bitterness,

  • remove the spines that grow on the leaves

  • and stems of wild varieties, make them tastier for us.

  • The tomato that's shown here

  • lacks the tomatine and solanine toxins that are present in its wild relatives,

  • which are all members of the poisonous nightshade family.

  • If we look at oil, it's true that olive oil is the only natural vegetable oil

  • that can be harvested without synthetic chemicals.

  • Except, it still requires at least rudimentary presses to remove it,

  • something that no Palaeolithic person would have ever built.

  • This is a farmer's food.

  • This is a model diet I found on a website.

  • It looks like a delicious and nutritious breakfast,

  • but a Palaeolithic person wouldn't have had access to it.

  • First of all, the blueberries are from New England,

  • the avocados, from Mexico, and the eggs, from China.

  • (Laughter)

  • This would have never appeared on any Palaeolithic plate.

  • And last, we have this problem of size.

  • Domestic blueberries are twice the size of wild blueberries.

  • We've already talked about bananas; you look at avocados.

  • A wild avocado has maybe a couple millimetres of fruit on it,

  • and the same goes for wild olives.

  • And of course chickens, chickens are prolific producers.

  • They lay eggs almost every single day.

  • They're predictable, large and abundant.

  • If you're trying to collect wild eggs, they don't lay year round,

  • and they're not as easy to find, they're typically small.

  • But maybe you're not convinced,

  • so I'm going to give just a couple more examples.

  • This, you may all recognise as broccoli.

  • Broccoli did not even exist in the Palaeolithic period.

  • What you see on the left is wild broccoli - looks quite different.

  • Now, wild broccoli is also: wild cabbage, wild cauliflower, wild kale,

  • wild kohlrabi and wild Brussels sprouts, they're all the same species.

  • The only difference is they're different cultivars.

  • We've selectively bred the same species

  • to produce the kind of food that we like best.

  • These are human inventions.

  • Broccoli, I think, is an interesting example because it's this weird thing.

  • What even is broccoli?

  • It's such a strange looking vegetable.

  • (Laughter)

  • In case you don't know, it's flowers, the flower of the plant.

  • We've changed this wild plant

  • into something that produces so many dense flowers.

  • It produces this odd, stalk-like thing, but it is flowers.

  • If you don't believe me, buy some broccoli at your grocery store,

  • put it in a vase, like I did on the right, and it will bloom.

  • It makes a lovely, lovely bouquet.

  • (Laughter)

  • So let's talk about carrots next.

  • You all recognise the carrots on the right,

  • but wild carrot is what's on the left.

  • It contains falcarindiol and other things that are natural pesticides.

  • They're bitter in flavour and they taste really bad,

  • and we've bred them out and we've also expanded them

  • made them much bigger, much sweeter, and much more full of vitamins,

  • because that's what we want.

  • Many of you may not know this,

  • but almonds and apricots