Primal Instincts or Paleofantasies?: A conversation with Dr. Marlene Zuk.

Joshua Brandt: I'd like to welcome Dr. Marlene Zuk, a professor of ecology, evolution, and behavior at the University of Minnesota to the Beneath the Skin blog. She's the author of "Paleofantasy: What Evolution Really Tells Us About Sex, Diet, and How We Live," a book which I found very illuminating and insightful. She's also the author of the recently released "Dancing Cockatoos and the Dead Man Test: How Behavior Evolves and Why It Matters." Welcome, Dr. Zuk.

Dr. Marlene Zuk: Thank you.

JB: I've had your book for a few years now, and it's got a lot of highlighting. Before I launch into any specific questions, I'll start with a general question: what was your primary motivation in writing the book?

MZ: I'm an evolutionary biologist and I’m really interested in how and why people think evolution is important in their lives. I have become increasingly aware of how many parts of our lives — whether it's our families, or how we eat, or how we exercise — are either implicitly or explicitly affected by the way we think evolution works.

I’m also a teacher so I'm interested in some of the misconceptions that my students have about evolution. So, that's some of the general background. Also, there are so many really extraordinary, cool new discoveries about human evolution. Increasingly, evolutionary biologists are aware of how fast evolution can happen and that was another theme that I wanted to explore.

JB: One of my favorite quotes from your book seems to get to the crux of the issue.

"The notions that humans got to a point in evolutionary history when their bodies were somehow in sync with the environment, and that sometime later we went astray from those roots — whether because of the advent of the agriculture, the invention of the bow and arrow, or the availability of the hamburger — reflects a misunderstanding of evolution."

MZ: Yeah. I felt like I was seeing a lot of people who would talk about the importance of evolution, but didn't really grasp how it works.

JB: What accounts for this myth making of the Paleolithic era?

MZ: (laughing) I blame it all on the cartoons. You know the one: there's a fish that turns into an amphibian and starts crawling on the land, and then the amphibian gets four legs and starts walking, and then you end up with a monkey-like thing, and then finally you end up with a bipedal. Then the cartoon concludes with a guy and a spear. (laughs) It's always a guy, and there's always a spear involved. And they usually look really noble and fit.

There's this sense that these people knew what they were doing...and after that it all went terribly wrong. That's usually the caption on the cartoon. Which is why the cartoons often conclude by showing some guy with a paunch slouched over his desk or clutching a fast-food bag. The implication is that we kind of reached our evolutionary peak back then, and it's all downhill from there. But that's not how evolution works.

People have always had a nostalgia for the past. It's just what that past is that differs. You know..."life was better when we were kids, or before the Industrial Revolution, or when we were hunter-gatherers." There's always been this sense that life was better when people were doing blah, blah, blah....

I think we're seeing this a lot now with idolizing indigenous people from various parts of the world and assuming that they really understood how to live in harmony with nature.

JB: Let me parse that a little bit. Why do people mythologize this one particular era?

MZ: I'm not sure it's this one particular era. I mean, I'm old now, and I have a sense of kids these days. There's a tendency to think it was all better when we were young, and no one was making sure our lives were over-scheduled, going from soccer practice to this club to that club, all so we could get into the best college.

I do, however, think that people that are interested in physical fitness assume people used to be in better health. And for some things, they're right. There are the so-called "diseases of civilization." Higher rates of diabetes, for example, and some cardiovascular issues are more present. So, by certain measures, you can say that people living in pre-industrial societies were healthier.

People who grew up before there were processed foods or modern inventions had lower rates of some forms of cancer (but not others) and lower rates of diabetes. So, OK, that's true. But there are also other things that are not as convenient with that narrative. The (Paleolithic people) also died of sepsis because there were no antibiotics. Their teeth were a mess because they ate things that broke them. Things of that nature. So, there's always this kind of push-pull when you discuss the past. Whether it's just nostalgia or something else is an interesting question.

JB: Speaking of "kernels of truth," let's talk about the study that the anthropologist Amanda Henry recently conducted. From your book, you wrote that Henry analyzed the plaque "clinging to the teeth of Neanderthals," which contained evidence of grass seeds, date palms, and evidence that grains were cooked and transported — which would seem to contradict the theory that there were no grains, or heating, or anything of that nature in the Neanderthal diet. (1)

MZ: First of all, let's pause to be amazed that they can get that kind of information off of fossilized plaque. How cool is that, right? I just think some of the work being done in this area is just extraordinary. So, let's just have a little moment of appreciation for studying plaque on teeth.

JB: (laughs) OK.

MZ: I think people mythologize things without any evidence. Maybe their idea of Neanderthal life came from "The Flinstones" or something similar. So, the thinking is just that they just ate meat back then. But anyone that's ever looked at contemporary foraging societies —or to the extent we can derive information from more ancient foraging societies — will see that people ate lots of different things. Some of them focused primarily on animals as a form of food, and some didn't. Anthropologists are still hotly debating the degree to which meat was the most important source of food for our ancestors, and the degree to which there was sexual division of labor.

One thing for sure is that human beings were able to get a lot of different nutritional sources from their environment. So, you know, the myth that humans were living on meat and animal product alone is exactly that — a myth.

JB: On that note, I'd really like your help in clarifying a couple of concepts that are outside my realm of expertise. There's the theory of "environment of evolutionary adaptiveness," and, conversely, the theory of "adaptively relevant environment." You mention both in your book. What differentiates them?

MZ: Those are ideas about how people evolved in a certain environment. We know human beings originated in Africa, and that's about as well established as anything we can do with our current information about ancestry.

From that, some people decided that our "natural " (and I'm using air quotes here) environment is the environment of the Savannah. You know, it's got the foods of the Savannah, the predators of the Savannah, etc. Therefore, that means we evolved to be adapted to that environment, which is true, but then people extrapolate from that to thinking that's the one environment that we were perfectly suited to live in, and that part is not true.

JB: So, the Savannah theory is the "environment of evolutionary adaptiveness?"

MB: Yeah. The idea of EEA is that that's the environment we were best suited for, because our genes changed as we became better and better adapted to it.

JB: So, the "adaptively relevant environment," is a rebuttal to that theory?

MZ: I'd call it more of a refinement of the theory. The idea of being adapted to our original environment is a reasonable one. But remember, evolution isn't static. The environment changes, and so we can be adapted to lots of different things.

I think a big part of the problem is how people colloquially use the word "adaptation." We use it as a synonym for being used to stuff.

Evolutionary biologists use it in a very particular, narrow way. We call something an "adaptation" if it has a particular trait, such as being bipedal. It's a genetic change in our bodies that resulted from natural selection acting on individuals. For example, two legs being better suited for their natural environments than walking on all fours.

But people use the word more colloquially to mean they've become adapted to drinking a milkshake every day. Evolutionary biologists mean something different. It's something that's happened to your genes that makes you better suited to whatever environment we're talking about. We're not using it in the sense that you've just gotten used to something.

The idea that there's this environment that human beings were perfectly adapted to contains within it the idea that everything stopped — and everything that's not related to that environment means we're misfits.

JB: Right. OK.

MZ: I and lot of other people would argue against that. We can become adapted to lots of different things, because evolution can actually happen really quickly and we can show these changes in our genes as our environment changes, because it's a lot more dynamic process than people realize.

JB: OK. I think I'm grasping it a lot better. If this is an accurate paraphrasing, please let me know. The first theory, the "environment of evolution adaptiveness" is more of a fixed idea — that at a certain point in time we're frozen in time with our genes and the expression of those genes and that’s it.

MZ: Yes. Right.

JB: And the second one, the "theory of adaptively relevant environment" allows for more of a dynamic, evolving expression.

MZ: Bingo. And the second theory reflects increasing awareness on the part of a lot of biologists that evolution really hasn't stopped. And yes, it's been the relative blink of an eye since the Pleistocene, but still plenty of time for stuff to change.

JB: So as a personal trainer, obviously I am very interested in a lot of the thinking and the misconceptions of exercise and movement. One of things that I’m constantly grappling with is, especially for newcomers to movement or fitness, is that they've read something or they know of a trend, and the thing they invariably mention is HIIT training or "high intensity interval training."

MZ: Oh, yeah. Right.

JB: As a newcomer to fitness, that amount of exertion is going to be very, very difficult to sustain. It's not going to work.

MZ: Really?

JB: It's antithetical to our nature. We're not wired for it. But the Paleo enthusiasts would say...no, actually we are wired for it. We're wired to run like hell when we see saber-tooth tigers, which is the HIIT training of the Paleolithic era.

MZ: (laughing) Yeah.

JB: (laughing) Of course, the reality is that there are no saber-tooth tigers in my neighborhood. Can you elaborate a little bit more on that line of thinking?

MZ: So, first of all, I'm very interested to know you're not a fan of the HIIT training. I go to the gym, and I'm interested in fitness. And I've heard all the stuff going back and forth on this. So...sidebar, tell me why you think that HIIT training won't work for newcomers? Is it that they're not able to pump out that level of intensity?

JB: I don't think it works for a majority of people. Having said that, many of my clients come from athletic backgrounds, and we do HIIT training. But they have a narrative of fitness, or a background in sports that allows them to do that.

MZ: Interesting. Whereas the New York Times health section will have an article about how everyone should be doing HIIT training. And that way, you'll be just as fit exercising for twenty minutes three times a week as you will be exercising for an hour each day. I've always thought that sounded really weird, although I admit I haven't tested it on myself. (laughs)

JB: Well, the paleo enthusiasts you cited in the book would make the correlation that running from a saber tooth tiger, or butchering an animal or lugging a bunch of rocks is what we should by trying to replicate.

MZ: Yeah, so again, there's this kernel of truth to that. It is almost unquestioned that our ancestors were more active than modern, Western industrialized society human beings. I'll give you that.

JB: Well, there's the rub. Lack of exercise doesn't equate to lack of activity, as you point out in your book. Two different things.

MZ: Exactly. First of all, everyone is always using the saber-tooth tiger in their examples. That just cracks me up. I mean, how many saber-tooth tigers do you think there were, and how often do you think they chased you – and you didn't get caught? Seriously, like, did this happen every single day? I just don't think society was like that. Cortisol levels must've been through the roof. (laughs)

So, I think there's a lot of taking Paleo concepts to the extreme. I read this one elaborate description of a Paleo exercise routine that involved moving all these heavy rocks, and I thought "where were they moving them to?" If they were living in caves, then the rocks were already there, right? This stuff descends into being absurd pretty quickly the minute you get a little more granular about it.

So, if you hadn't run from a saber-tooth tiger in two weeks, you were out of shape? I think those theories lose a lot of credibility when you examine them more closely. If you actually look at contemporary modern foraging societies, they're more active. What are they doing? Walking, digging up tubers, playing etc. But, none of them have large mammalian predators running after them, and they seem to be doing OK.

JB: (laughing) On that note, there's a famous study I wrote about called The Double Decker Bus Survey. It was conducted by Jeremy Morris in the late 1950s in the U.K. He tracked both ticket takers and drivers on the bus and, regardless of factors such as smoking or weight, the ticket-takers were half as likely to suffer from coronary heart disease as the drivers. (2)

This is a segue into the NEAT (non exercise activity thermogenesis), which I mention in the article, and which you also detail in your book. So, I've always promoted the viewpoint that consistent low-grade movement is going to be better than brief intervals of high-intensity training.

MZ: Well, here we're definitely outside my area of expertise, because I'm not an exercise physiologist. But you do see that "small bursts of intense activity" being heavily promoted. You know, the studies of people riding their bikes at maximum speed and aerobic capacity and then stopping for twenty seconds versus someone who rode at a reasonable pace for a half-hour. You measure something in them, and the first group seems to have better results.

Once again, I'm not an exercise physiologist. So, what do you think about those studies?

JB: Well, "better" is kind of a nebulous term...

MZ: Absolutely.

JB: Some of those studies I've cited in a previous article. In the study footnotes, they state that the subjects were already at a certain athletic level, because they were the only ones that could sustain that level of exertion. You can't take consistent couch potatoes and subject them to maximum exertion tests. (3)

MZ: Oh. Interesting.

JB: Yeah, I think that's a really important caveat.

MZ: So, do you ever get someone coming to you and saying "I've been a total couch potato, and I need help?

JB: (laughing) Well, we're switching roles. The interviewer is being interviewed.

MZ: (laughs) Yeah. Why not? Hopefully that's OK.

JB: Well, yes I do...but it gets kinda complicated. If it's a newcomer to fitness, I'll ask them what the main goal is, and they'll say "weight loss," or, more accurately, "fat loss." That's a difficult thing to sustain through exercise alone.

MZ: Right. Yeah.

JB: So, I'll often recommend to people that they place functional goals first and make aesthetic goals secondary. Aesthetic goals can be elusive. You know... "I want to look like this" or even "I want to weigh a certain number." Well, my response is "How do you know you want to weigh that number? What's attached to it? Are there any studies that show that's the optimal weight for longevity? Do you feel much better at that number? Is it sustainable?

I think success is much more sustainable with functional goals. You know...I want to be stronger, more flexible, move better, be injury free, pick up my kids. Stuff like that. Those are all goals I feel confident I can help people achieve as a personal trainer. But if the goals are more ephemeral, that's going to be more difficult to accomplish.

MZ: Yeah, that completely makes sense.

JB: That's a good lead-in to my next question for you. One of the things that I had a good chuckle about when reading your book is all the Paleoenthusiasts who disparage "chronic cardio." As an avid cyclist, I found this very interesting. I suppose the thinking is that chronic cardio should be avoided because it relies on carbohydrates as a source of quick and efficient fuel, which is bad because it leads to weight gain.

I think there's a few words missing. I think most people are suffering from a chronic "lack of" cardio. Any thoughts on that?

MZ: Well, I know when I got to the gym and do cardio I never think "God, I wish I hadn't done that." I say that about a lot of other things, but never about going to the gym. I always feel great afterward.

JB: That's a great point you just raised. The "feeling" you get. I think that's a key word. I don't cycle to get a six-pack. I cycle to clear my head, and because I feel great afterwards.

MZ: Exactly. Yeah. You know, I'm not a competitive athlete at all, but I've found my happy place when it comes to fitness, and that's OK. I practice yoga as well, and I'm always amazed by the diversity of body shapes in there. So, I think the philosophy of there "just one path" isn't really helpful when it comes to fitness.

JB: Yeah, that's the reason I brought it up. There's this thinking that "chronic cardio" is really foreign to our nature. In your book, you cited the Bramble/Lieberman study which is called the "Endurance Running Hypothesis." which contends that our Paleolithic ancestors ran long and hard enough to hunt and catch prey, and the protein and fat consequently enabled the development of our brains. (4)

MZ: Yeah, the chapter about exercise was the most interesting for me to write, because I had zero preconceptions going in. The other topics I was much more familiar with. I'd never read "Born to Run" and I'm not a runner. I always say, "I'll run if someone is chasing me. And even then...are they armed?"

JB: (laughs)

MZ: I met Lieberman. He's a super guy. Really interesting. Have you talked with him?

JB: He's definitely on the list.

MZ: I met him at a conference and told me he was glad I wrote the "Paleofantasy book" so he didn't have to. (laughs) I think the idea that long distance running is part of our evolutionary heritage is super interesting and they've marshaled some really cool evidence.

JB: In writing the book, did your research influence your thinking or activities?

MZ: Not so much, for the reasons we discussed earlier. A lot of the people that are really into the whole "here's the plan for your fitness, your diet, how to be a better parent, etc. are just so prescriptive about what you can do, and lot of it isn't taking into account the huge amount of variability in human behavior or how people live. People live very happy and fulfilling lives eating a variety of diets and doing a variety of activities.

I do actually feel vindicated by the NEAT studies mentioned earlier. I'm a very twitchy person, and I move around a lot. (laughs) Apparently, that's helpful.

JB: (laughs) Yeah. That's what the science says. I do have one more question for you. I really enjoy chocolate mousse. From an evolutionary perspective, do you think it's OK if I continue eating it?

MZ: (laughs) I absolutely do. Although you should probably eat other things as well.

JB: OK. Well, thank you for your time, Dr. Zuk. It's been a real pleasure.

MZ: Thank you. I enjoyed it as well.

Sources:

(1) Amanda G Henry, Alison S Brooks, Dolores R Piper (11/12/2010) "Microfossils in calculus demonstrate consumption of plants and cooked foods in Neanderthal diets." Proceedings of the National Academy of Sciences 

(2) https://beneath-the-skin.ghost.io/n-e-a-t-2/

(3) https://beneath-the-skin.ghost.io/epoc-the-loch-ness-monster-of-fitness/

(4) Dennis M Bramble, Daniel E. Lieberman (11/18/2004) "Endurance running and the evolution of Homo" Nature

Correction: The sentence by Dr. Zuk that read "And that way, you'll be just as fit exercising for twenty minutes three times a day as you will be exercising for an hour each day," should've read "And that way, you'll be just as fit exercising for twenty minutes three times a week as you will be exercising for an hour each day.