We – we anthropologists, we scholars, we folk who act like we know what we’re talking about – tend to talk about complicated phenomena in ways that simplify them. This is necessary in teaching, in public outreach, and even in presenting work to our colleagues. We need to first make ourselves understood and then to try to come ever closer in our approximation to the real complexity of an idea or phenomenon. These technically untrue approximations of complex truths are sometimes called “lies to children”.*
Talk about evolution tends to be replete with metaphors about natural selection. We talk about the “goals” of evolution or the “choices” that species or individual genes make, even if we don’t believe that there is any intelligence at work in the process. Even talk about the “reasons” for a particular evolutionary outcome are usually imprecise approximations.
I was thinking about all of this after listening to a recent Fresh Air radio broadcast. Terry Gross interviewed Daniel Lieberman, Harvard professor of human evolutionary biology, about his recent book, The Story of the Human Body.
Now I hate to complain about this. I am pleased when news media interview scientists directly rather than relying on journalists or publicists to explain scientific work, and Fresh Air works hard to get excellent interview subjects. But while listening to the interview I was deeply uncomfortable about the ways Gross and Lieberman talked about evolution. It was really more of a feeling than a well-formed idea at the time, so I went back later and listened again to the podcast of the interview to try to understand what made me so uncomfortable.
I’m still thinking about the question of what made me feel that there was something misleading in the description of evolution, but this is a first approximation.
Lieberman and Gross discussed how changes in human diet and lifestyle lead to “mismatch diseases”, non-infectious, lifestyle-related illness. I’ve transcribed part of the interview to illustrate two issues.
Terry Gross: Why are our bodies ill-equipped for the kinds of foods and fats and sugars, and the quantity of food that we’re eating now?
Daniel Lieberman: Yeah well this is an important topic, obviously. You know, in India and China for example rates of diabetes are going up by almost an order of magnitude over the last generation, and they’re going up very rapidly in the US, too. And the reason they’re mismatch diseases is that diabetes, for example, is caused by essentially the body being unable to cope with sugar in the bloodstream. So, we evolved to crave sugar because sugar is an energy-rich food, but we didn’t evolve to digest large amounts of it rapidly.
Gross: So our bodies, the basic operating system of our bodies was designed for the hunter-gatherer era, right?
Lieberman: To a large extent. I mean hunter-gatherers, and even before hunter-gatherers, chimpanzees for example, eat plenty of foods that have carbohydrates. For example chimpanzees eat almost all fruit, right. … [But] Most wild fruits are only about as sweet as a carrot. So we love sweetness, but until recently pretty much the only food that we got that was very sweet was honey, and honey of course was a special treat. That was pretty much the only form of dessert in the paleolithic.
(The bit I’ve left out, marked by the ellipsis and bracketed [But], is Lieberman’s description of the sugars in fruit.)
There are two problems I see here. One problem is that Gross’s second question and it’s evocation of “the hunter-gatherer era” seems to suggest a view of evolution more in tune with Herbert Spencer than Charles Darwin, let alone contemporary evolutionary biology or anthropology. For Spencer and some other nineteenth century thinkers, evolution was thought to have a goal, a specific end-point. In biology, the “survival of the fittest” (Spencer coined the phrase) ensured that “higher” species would survive while “lower” ones eventually failed to reproduce. In human societies, hunting and gathering would give way to agriculture, and eventually to industrial “civilization”. Such theories were the the cause of, shall we say, considerable problems with early anthropology.
Now I have no reason to believe that Lieberman or Gross subscribe to such notions of evolutionism or social Darwinism. But the presupposition that there was, and no longer is, a “hunter-gather era”, and the failure to note the presupposition as problematic, may have contributed to my discomfort.
A second problem I see in this excerpt is its treatment of time. According to Lieberman, the mismatch he is describing has developed “over the last generation”, but also since “the paleolithic”. (No matter what my nieces may think, we were not actually living in the Stone Age a generation ago.) There is even a suggestion, in the discussion of chimpanzees “even before hunter-gatherers” that this mismatch developed around the time that the Homo and Pan genera diverged. So the problem of mismatch diseases is approximately 20 or 15,000 or 2.5 million years old. That’s a pretty rough estimate.
Now as I said, this kind of rough, even technically false approximation is a necessary step in explaining complex phenomena, and I shouldn’t criticize anyone too strongly for failing to get into all the messy complexity of advanced scholarship in a half-hour radio broadcast. Nevertheless, it makes me uncomfortable.
Lieberman’s answer to Gross’s last question suggests that he is able to explain things in a way that even I will not find discomforting.
Gross: Have we stopped evolving?
Lieberman: Definitely not. Evolution is always churning along. Evolution, after all, is just change over time, and natural selection, which is the kind of evolution we tend to be thinking about the most, is caused by just a few phenomena that are always there. … [But] what’s a more dominant form of evolution today is cultural evolution. It’s how we learn and use our bodies and interact with each other based on learned information. And that’s also a kind of evolution. It’s not Darwinian evolution, it’s not biological evolution, but it affects our bodies. We’re evolving slowly through natural selection and rapidly through cultural evolution.
This, I fancy, captures Lieberman’s point nicely. Biological change through natural selection is slow, while cultural and technological change is fast. This suggests one possible treatment for my current discomfort. I’ll need to go out and read Lieberman’s book.
*Wikipedia says that the label “lies-to-children” is due to science fiction author Terry Pratchett. Who knew?
Chad, good comments/analysis. Alas, I think the problem is much worse than that, and I’m someone who started out as a pretty hardcore evolutionary biologist and still finds it a compelling body of theory and evidence with a great deal of relevance. But just not in the way normally conceived.
Just as Jason Antrosio is discussing how the short-hand on “culture” really limits anthropology, so too does the short-hand for talking about evolution. They try to present it as a common sensical idea, but at its core, evolution is precisely not that, particularly for Western mentalities. My personal pet peeve is people who talk about evolution (or natural selection) doing this or that, for example, as designing us in certain ways. It makes evolution sound like some greek god, looking from on-high and shaping the clay of humans into some desirable form. And that’s just wrong. Evolution by natural selection works as a process, responding to certain necessary conditions and proceeding almost inevitably from that – but without some predetermined direction. Direction actually comes from phylogeny (or evolutionary history) and ecology, not from natural selection itself.
All that means, for me, that this sort of statement “the basic operating system of our bodies was designed for the hunter-gatherer era” is really stupid. If anything, the basic operating system of our bodies is much, much, more more ancient than that, and that really matters. Just not in the way most evolutionists will portray it, because this approach makes it harder to weave an effective story. It’s a better story, full of more drama and sub-plots, and with greater complexity, but most of these scientists haven’t caught up to Game of Thrones yet in how they do their scientific thinking. Always the straight-forward way…
I also really don’t like the unsubstantiated assertions that can come out of evolutionists’ mouths (and culture-and-power people too…). So take Lieberman, “diabetes, for example, is caused by essentially the body being unable to cope with sugar in the bloodstream. So, we evolved to crave sugar because sugar is an energy-rich food, but we didn’t evolve to digest large amounts of it rapidly.” That’s a blanket statement, with the implication that the cause is evolutionary. So, tell me, just how did sugar get everywhere in modern post-industrial society? Sidney Mintz might have a few things to say here that are more pertinent than Lieberman’s mismatch. Why the heck is there a mismatch? It’s not because our biology hasn’t caught up. It’s not even quite that our biology gets exploited for profit. But certainly that’s a more relevant line of analysis.
Along this line, I’d like to see some actual data on what’s going on with diabetes, not just a quick assertion. I’ve gone through this with addiction. A harder type of analysis is actually to come face-to-face with the biology, to really look at what’s going on, and then to try to think how evolutionary analyses might be relevant. Often they aren’t, but many times they can be helpful in cutting problems down to size or providing insights that you can’t get from other bodies of theory.
But the evolutionists are really mistaken if they think cultural evolution research (a fascinating topic) will get them as far as some of them secretly hope (taking down those pesky cultural anthropologists who are anti-science). It’s apples and oranges. Culture affects our bodies, that seems to be what Lieberman is saying there, which is something that we should celebrate him saying. But the way to understand how it does that is not necessarily through looking at cultural evolution in the past. Tackle the problem more directly, it’s likely to be more revealing.
Daniel wrote: “My personal pet peeve is people who talk about evolution (or natural selection) doing this or that, for example, as designing us in certain ways. It makes evolution sound like some greek god, looking from on-high and shaping the clay of humans into some desirable form. And that’s just wrong. Evolution by natural selection works as a process, responding to certain necessary conditions and proceeding almost inevitably from that – but without some predetermined direction. Direction actually comes from phylogeny (or evolutionary history) and ecology, not from natural selection itself.”
Yes! Culture, on one hand, gets butchered and turned into some sort of almost-genetic entity that controls people’s behavior whether they like it or not, and evolution, on the other, gets turned into some directed, reasoned force that actively shapes biology. It’s strange that people think about these concepts in this way so often, but that’s the lay of the land. But there is no reason to evolution–didn’t everyone have to watch those great lectures on VHS of Stephen Jay Gould hammering the point that there’s no such thing as progress in evolution, let alone predetermined direction or purpose? The idea that humans were purposefully designed to be hunter-gatherers has about as much validity as saying that they were designed to sit around in dark rooms all day drinking 80oz sodas playing video games!
Thanks for the post, Chad. Good stuff.
Hello. I’m a lowly postgraduate student so please forgive me if I’ve got the wrong end of the stick here. I just have a few questions about some of the points you made:
“Gross’s second question and it’s evocation of “the hunter-gatherer era” seems to suggest a view of evolution more in tune with Herbert Spencer than Charles Darwin, let alone contemporary evolutionary biology or anthropology. ”
Is it not accepted that the human environment of evolutionary adaptedness, namely the typical environment of the Paleolithic, was chiefly responsible for creating the selective pressures that led to our current biology? I think this is what biological anthropologists are referring to when they speak of the “hunter-gatherer era”. Nowhere do Gross or Lieberman suggest that they approve of any form of Spencerism, whereas the existence of particular periods of evolution is widely accepted in evolutionary biology and anthropology.
“Now I have no reason to believe that Lieberman or Gross subscribe to such notions of evolutionism or social Darwinism.”
Why do you compare them then? Such comparisons, in my experience, only serve to confuse people and distance them from the science behind evolution, which is in no way value-laden.
As an aside, many evolutionary scientists do no consider the term “evolutionist” or “evolutionism” to be pejorative, e.g. http://evolution.binghamton.edu/dswilson/
[“Evolutionism” is often used as a synonym for “social Darwinism”, though clearly it has other uses as well. As I intended the word it is not a comparison; it is a tautology. I’m not certain how Dr. Wilson intended the related word “evolutionist”, but I dare say we had different meanings in mind. -CDN]
“But the presupposition that there was, and no longer is, a “hunter-gather era”, and the failure to note the presupposition as problematic, may have contributed to my discomfort.”
Does the presupposition that there was, and no longer is, a “Paleolithic period” contribute to your discomfort too? I have never heard of a biological anthropologist who denies that there are still hunter-gatherers around today.
“A second problem I see in this excerpt is its treatment of time. According to Lieberman, the mismatch he is describing has developed “over the last generation”, but also since “the paleolithic”.”
Lieberman may be suggesting that mismatches have two halves: our biology, and our environment. Evolutionary anthropologists suggest that our biology has not changed considerably since the Paleolithic (though that is certainly not to say it hasn’t changed at all). Environments, on the other hand, change far more rapidly (as you note in your last paragraph). Access to artificially sweetened foods has indeed rocketed “over the last generation”.
I’d be really grateful to hear what you think of these comments. And thanks for the article!
All the best,
Dougie
Great post, Chad, and just a few thoughts. I might come back when I have a bit of time (bad week here with competing obligations at work).
I agree with what you’re saying, especially your first objection, but I would put it this way. The idea that we are ‘designed for hunting and gathering’ or any other specific situation assumes that our ancestors were perfectly adapted to a prior niche and that we no longer are. In fact, they were not perfectly adapted to hunting and gathering.
A theorist alive 500,000 years ago might look around at all the bone breaks, meat-specific parasites, and premature deaths from hippopotamus tramplings and say, ‘well, our ancestors were perfectly adapted to scavenging and eating fruit and running from predators, but our new modern hunting life means there’s a mismatch between our bodies and our way of getting food. That’s why we have all these injuries, all these strange meat-borne parasites, etc.’ And then the 500 kybp evolutionary psychologist could talk about an Environment of Evolutionary Adaptedness to scavenging and all the problems caused by a conversion to life as hunters and gatherers.
But then you could just push that back further, to 3 mya or so (I’m just riffing, so don’t quote me on hypothetical dates) and our early-early evolutionary theorist could say, ‘Look, all these medical conditions we get, these carrion-borne parasites that our ancestors never experienced, these deaths from raptors taking our children, these problems we have with arthritis in the knees, etc. — they’re all a result of our modern, non-arboreal lifestyle and our shift to a wholly bipedal life. Our ancestors were originally adapted to a life in the trees of fruit eating, where raptors could not get us…’ And this 3 mybp evolutionary psychologist could wax poetic about the fitness of the now-mismatched hominin physiology to an earlier time period and an earlier set of demands on his or her ancestors…
That is, Dougie, at least if I’m reading Chad right we agree on this: there’s just no beginning point to this whole discussion. There’s no time when there AREN’T ‘mismatches’ between environment and organism because adaptation is NOT design. So, no, the problem is not that people don’t agree that the EEA was the Paleolithic; it’s that a lot of evolutionary theorists think that the EEA CONCEPT is not consistent with evolutionary thinking. It is not that we disagree about human evolution; it’s that the EEA is not a good evolutionary model. And it’s not that adaptation is not important, it’s that constraint and inheritance, including ‘mismatches’, is crucial.
Many of the problems of diet and the like today are not because our ancestors were perfectly adapted to this or that environment in their evolutionary history, but simply a result of much older, longer-term processes and evolutionary endowments that date back, not a million or million-and-a-half (or 80,000) years, but much, much longer. Our ancestors actually proved to be a strikingly invasive ape, capable of surviving in a wide range of ecological niches — adaptation to any one of them was unlikely.
And there’s simply no reason to focus on one period’s ‘mismatch’ over the ‘mismatch’ that is inherent in an evolved physiology. ‘Designed for’ is a metaphor better suited to creationism than to evolutionary thinking. Yes, it highlights adaptedness, but also makes adaptation-ism — the assumption that any and all traits are always adaptations, with no focus on other mechanisms of change OR on constraints to adaptation — almost inevitable in simplified accounts.
I wrote my own critique of sloppy ‘design’ thinking in popular accounts of evolutionary theory a few years back, in a piece titled ‘Sympathy for creationists’: http://neuroanthropology.net/2009/09/23/sympathy-for-creationists/
I’m probably as guilty as anyone else of using the design metaphor, but maybe being a cultural anthropologist makes me more sensitive to the biases and limits of metaphorical thinking. Chad’s right, as far as I’m concerned, that an otherwise great interview and good questions can start to go off the rails when the metaphor is let to get control of the thinking too much.
Ah, the amateurs chime in.
Just off the top of my head, wouldn’t most creatures be mismatched, as it were, and hence evolution. I’d think that sharks, for example, which—if I have this right—are very stable and haven’t evolved much in millions of years; they would be well matched to their environment. Critters like us, always changing, would imply that we’re continually adapting to new circumstances, no? Sort of like mismatching leading to evolution, yes?
Johan
It seems like the everyday language of evolution is saturated with teleological metaphors and instances of misplaced concretism. It’s even in quite a few of my textbooks. What I find particularly interesting is the degree to which people adapt (or don’t) when the problem is explained to them. Some people seem to accept that the language is figurative at best, but others insist on taking these features quite literally. What makes the difference isn’t always clear.
In rereading the article and responses, it would seem like the idea of adapting to anything is not what evolution does. I can’t picture evolution as anything except opportunistic; and opportunism isn’t adapting so much as “taking advantage of.” One doesn’t evolve in a particular direction because it would be a good idea. One evolves a particular trait because one is able to and the evolved trait improved life chances. There are, theoretically, an infinite number of mutations that could have improved those chances as much or more, but they didn’t happen because chance didn’t lead that way.
And, I suppose, there’s the question of how selection works and what role diseases have in the natural selection process. Who’s to say that diabetes, over time, couldn’t kill off those people poorly equipped to process large amounts of sugar?
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