Links this week:

1. There have been some strong reactions to the Edge piece on Napoleon Chagnon (I pointed it out last week, and if you haven’t yet, give it a look). Some are entertaining, although most are not particularly enlightening. Jason Anstrosio goes the epigenetics maneuver and Stephen Corry pins death rates among ancient hunters on hunting accidents.
2. If you’re risk averse, don’t do science – become an actuary.
3. The Faroe Islands Health Ministry plans to genetically sequence everyone on the island who wants it.
4. Overview of the Flynn effect (unfortunately gated if you don’t have journal access).
5. George Monbiot on rewilding (audio download)

Gregory Clark opens A Farewell to Alms with a strong claim:

The basic outline of world economic history is surprisingly simple. Indeed it can be summarized in one diagram: figure 1.1.

I like Clark’s claim, but I’m now convinced that we need a second. From Michael Kremer’s Population Growth and Technological Change: One Million B.C. to 1990:

Figure I plots the growth rate of population against its level from prehistoric times to the present.

Even though there was negligible per person income growth through the Malthusian era, technological change was accelerating. As more people leads to more ideas (as there are more people to come up with them), a larger population leads to faster technological progress. Technological progress in turn allows for further population growth. The resulting pattern is faster than exponential growth in technology and population – a dynamic that does not show up in Clark’s chart.

If I were to stretch it to a third diagram I would want something that captures the dynamism of the Malthusian era – population bottlenecks, different rates of growth across different populations and the like – but I’m not sure what that chart would look like yet.

In a discussion on the rise of mental health issues at Core Economics, Paul Frijters touches on the increase in obesity over the last 50 years.

One can basically out of hand reject the excuses most individuals give for their problems as being the reason. The rate of increase rules out any reasonable role for genetics. The fact that the poor suffer more from obesity, whilst it is cheaper to eat less and whilst food has always been cheap for the rich, rules out any obvious effect of the lower price of food or the availability of fast-food. The sustained increase over a long time rules out any story depending on some major current crisis. Like it or loath it, but it is clear that one must look at ‘cultural factors’ to have a hope of understanding what is going on.

A big hint comes from cross-national differences amongst rich countries, where things like wealth and food affordability don’t differ much. As you can see here, the Anglo-Saxon countries, and then particularly the US, stands out. Whilst a third of adults in the US are now obese (with about 25% of Australian adults), only 4% of Koreans and Japanese are such, and in the more egalitarian Northern European countries (Sweden, Norway, Holland) rates are below 10%. The same holds for Italy and France, though rates in those countries too are quite a bit up from what they were 50 years ago. So your one major clue is that there are major unexplained differences over countries.

I’ve heard this “it can’t be genetics” argument from a few people recently. And in some respects it is right. Clearly, the genes in the population have not changed substantially over the last 50 years. However, to dismiss genetics in trying to understand obesity is ignoring an important piece of the puzzle.

First is the high heritability of obesity – both before and during the increase in obesity of the last 50 years – usually measured in the range of 55 to 85 per cent. This level of heritability exceeds that measured for most behavioural traits (although it is in the realm of heritability for intelligence). This suggests that both before and after the increase in obesity, genetics plays a substantial role in who is obese. As the environment has changed (such as the “cultural factors” that Frijters alludes to), people of different genotypes have responded in different ways.

Another pointer to the role of genetics is in the high levels of obesity and obesity-related diseases in some populations, particularly indigenous populations with a limited history of agriculture. Pacific islanders, with almost no history of grain based agriculture, have the highest rates of obesity in the world. American Indian and Alaskan Natives (as a group) have the second highest level of obesity in the United States of any major ethnic group (behind people of Pacific Island origin). In Australia, aboriginals and Torres Strait Islanders are twice as likely to be obese as Caucasians. The costs of obesity, such as Type 2 diabetes, also tend to higher for these groups.

Frijters’s point on the response of the rich and the poor to food prices also has a hint of genetic factors. These groups are not the same. The rich and poor differ in average levels of IQ, willpower, conscientiousness and a host of other traits with a genetic component (even if you don’t believe there is a genetic component, you still should not treat them as the same). So when we ask why obesity is higher among poor people (or less educated people), we should ask what role those traits and their underlying genetic influences play. When faced with the same choices, they are likely to select different options.

These traits might also be relevant for cross-country comparison. Should we be surprised that East Asian countries where populations have higher measured IQ, lower rates of time preference and higher savings rates also have lower rates of obesity? (Obviously, on a cross-national basis, this is not the complete explanation. For example, East Asians in the United States have higher levels of obesity than their counterparts still in East Asia, although they are obese at rates lower than Caucasians and other ethnic groups).

We should also not be too quick to dismiss price. It is not only absolute price that matters, but also relative price of different food types. As argued by Rob Brooks, Steve Simpson and David Raubenheimer, simple carbohydrates have never been cheaper relative to protein. If you are price sensitive, you may shift consumption towards simple carbohydrates. As someone who tends to avoid simple carbohydrates, I can also attest that a large part of the relative price of food is the search effort in finding a low carbohydrate option.

The reason this matters also has an evolutionary basis. Eating food is not a simple “eat calories and feel full” process. Different foods create different responses in appetite. Brooks and his colleagues base their argument on the protein leverage hypothesis, which is a hypothesis that humans have a stronger propensity to regulate protein intake than they do for other non-protein calories. Humans eat until we satisfy out basic daily protein need. If the food we are eating has low protein content, we need to eat more before hitting that satiation point. These extra calories are what make someone obese. Trends in carbohydrate, protein and fat consumption in the United States over the last 40 years offer support for this argument.

Arguments such as the protein leverage hypothesis also have interesting implications for any arguments about the willpower of the obese. Someone eating a diet high in simple calories would need more willpower to constrain their calorie intake than someone on a high protein diet.

While Frijters points to the cross-national differences as a major clue to why obesity has increased, the above suggests that within country and cross-population differences will also be useful. The cultural changes that have resulted in the increase in obesity play out in different ways depending on who the person is. Genetics is clearly not the only factor that should be examined – look at the Anglosphere compared to Northern European countries – but any cultural explanation will need to accord with the evidence that the cultural changes do not affect all people equally.

Links this week:

1. Pinker, Wrangham, Dennett, Haig, Seabright and friends on Napoleon Chagnon (including interviews with Chagnon).
2. Another Andrew Gelman swipe at those “Psychological Science”papers.
3. From late last year, but worth a read – John S Wilkins takes a look at sociobiology (Parts 1, 2, 3 and 4 follow) [HT: Åse Kvist Innes-Ker].
4. Like Zuk’s book, an interesting take on the paleo diet, but beating a straw man.
5. Rob Brooks and I have an article up at Evolution: This View of Life on the rise of “breadwinner moms”.

In my post on Marlene Zuk’s Paleofantasy, I referred to a review by John Hawks. Hawks suggested that Zuk’s fantasies should be thought of as hypotheses to be tested. I was not convinced that Zuk used this approach, but Hawks’s comment triggered me to write a list of what are the most interesting questions about the paleo lifestyle that I would like to see more evidence on. The list is below.

The common thought that runs through them, beyond Zuk’s points about recent evolution, is that adaptation to a particular diet doesn’t mean it can’t be improved. Also, humans faced broadly varied diets in our past, so I expect that humans have much flexibility in what we can eat.

I should also note that I am posing these questions not as a challenge to the central tenets of the paleo diet, which I expect will largely hold. However, if the answers to these questions fall a certain way, the resulting dietary recommendations probably won’t be called paleo.

Finally, while there is already evidence on the likely answer for some of them, the questions are far from closed.

1. How does the performance of our mental hardware vary across different diets? I ask this for two reasons. First, we haven’t only evolved physically since the dawn of agriculture, but also mentally. Second, while the paleo-diet may be a good starting point, there must almost certainly be some ways it can be improved, particularly in the context of specific domains such as intelligence. [For me, this is the question I’d most like to know more about.]
2. How does the paleo-diet compare to the Mediterranean or the Okinawan diet in terms of longevity? Or other health measures? Evolution doesn’t shape humans to live as long as possible. It shapes us to have viable offspring. I should also throw in the growing evidence that the costs of carrying some extra fat are not as high as some people claim.
3. Following from this, what are the trade-offs? If a diet full of red meat improves health and reproductive success at some age points, does it increase cancer risk in old age? Is there a trade-off between physical and mental output? I am skeptical of claims of a world without trade-offs.
4. On the flip side to the above two points, what of Michael Rose’s argument that traits at different ages may not be directly linked, and selective forces act more strongly when we are young? Is a paleo diet more beneficial during old age, as the selective forces associated with agriculture have had less opportunity to shape traits that express when we are old? If we switch over to a paleo-diet at age 40, what costs of our pre-40 behaviour persist?
5. While there is plenty of evidence about the potential for human evolution since the dawn of agriculture, the potential for evolution of our microbiome is orders of magnitude larger. What is the effect of the changes in our microbiome? If someone eats a paleo diet, their microbiome is considerably different from when they were eating a diet full of sugar and grain. But how much does a paleo-diet microbiome today resemble the human microbiome of tens of thousands of years ago?
6. Grass seeds tend to be poisonous. But how much has the level of poison changed since humans commenced farming grains relative to our ability to digest those poisons? There is likely to have been significant evolution of grains if less poisonous varieties were selected for (and communities that farmed them would likely have had an advantage). Is rice really that bad?
7. How much of the benefit of the paleo-diet comes from simply excluding sugars and highly processed flour? If you read the paleo testimonials on sites such as Mark’s Daily Apple, I’m guessing most of the benefits came from cutting out the junk and getting some exercise. I’m sounding like Marlene Zuk here, but I’d like to see this tested.
8. How much of the benefit of the paleo-diet is due to calorific restriction? When the muffins or donuts get passed around at work, you say no. Not only are you excluding simple carbs, but you are also consuming less calories than you might have otherwise.
9. If we remember that most people hanging out on paleo-websites are the people for whom the diet works, what is the actual rate of attrition of people who chose a paleo diet as opposed to other diets? I know that I find the paleo-diet to be an easy to use heuristic, but is this the case in general?
10. How do the answers to these questions change as we look at people of different ethnicity with different agricultural histories? How much variation is there within these groups?
11. And an exercise question – how much variation is there in feet type between people and populations? Is barefoot running better for some people’s feet than others?

I’m sure I can come up with more, but these will do for the moment. Explorations of some of these questions would probably make a nice blog post, so I’ll revisit some of them soon.

For some time, the “Paleo” lifestyle has been due for a decent critique from the perspective of growing evidence about the rapid rate of human evolution. Humans have evolved markedly since the dawn of agriculture, with adaptations ranging from disease resistance to the improved ability to digest starch. So when I heard of Marlene Zuk’s Paleofantasy: What Evolution Really Tells Us about Sex, Diet, and How We Live, I was looking forward to that critique being provided.

And Zuk certainly provides a critique. She relentlessly pulls apart the ideas that we are well adapted to the Paleolithic environment, or that rapid environmental change means that there is mismatch between the environment and our genes. As Zuk points out, evolution does not result in stasis and there is no point at which we are ever completely adapted to our environment. We will always be a collection of bootstrapped responses to changing conditions.

However, Zuk’s critique was not the one I was hoping for. As was the case for the promotion pieces and reviews that I read before reaching the main course, Zuk parades a series of straw men rather than searching for the more sophisticated arguments of Paleo advocates. Many chapters begin with misspelled comments that Zuk found under blog posts. While Zuk shoots the fish in the barrel, the more interesting targets are not addressed.

In a Nature review, John Hawks suggests that Zuk’s use of the term ‘fantasy’ is a reference to hypothesis forming, where we play with hypotheses and try to falsify them. I tried to read the book in that light, but it is hard to do. Zuk appears so keen to throw Paleo-enthusiasts under the bus that she does not give many of the hypotheses the thought that they deserve.  At times Zuk seemed almost desperate to find someone to be on the other side of her debate, such as when she chose Ryan and Jetha’s Sex at Dawn as her punching bag for her discussion of sex differences, even though Ryan and Jetha are almost on their own with their thesis. Where she did write qualifiers about not everyone believing in the straw man that she was about to dispatch (which was often), she would proceed to torch the straw man as though the just acknowledged view did not exist.

Take the chapter on diet. Zuk points out that many humans have evolved lactose tolerance. Those with a longer history of agricultural diets have genetic adaptations to allow them to digest starch more efficiently. Even the foods we eat have evolved, with potatoes formerly bitter and lumpy, and corn having a shape and size more like a stalk of rice. But these are points most Paleo-advocates would happily concede. They are not seeking a historical re-enactment. Their argument is not that we have not changed at all, but that the changes have not been enough to make a diet full of grains and sugar superior to a diet of meat, nuts, fruit and vegetables. Whether that is the best diet could be the subject of an interesting debate (i.e. testing the hypothesis), but this is not the argument that Zuk engages with.

Moving to a more substantial point, a review in Evolutionary Psychology nicely summarises Zuk’s mismatch argument as being at three levels: there are no mismatches as all species are adapted to past environments, not current ones; even if mismatches occur, we are not in a position to understand them; and the mismatch perspective has not proven beneficial.

On the first of these, Zuk pushes too far by highlighting cases of rapid evolution while ignoring cases where mismatch does occur. Her description of the evolutionary bootstrapping that must occur when organisms encounter new environments points to the potential of mismatch. Zuk’s arguments about the difficulty in understanding mismatches leans towards saying it is all too hard, and not engaging in the sort of hypothesis testing that Hawks refers to. And on the point that the mismatch hypothesis has not proven useful, there are times where Zuk shows just how useful a mismatch perspective might be. She acknowledges that the high sugar content diet of the last 50 years is not something we are matched to, and provides some interesting points on barefoot running and the evidence of the cost of cushioned shoes. The mismatch between current and past physical activity (accompanied by the suggestion that people should simply “get off the couch”) is almost too obvious to mention.

Having said all the above, I still enjoyed the book. There is a lot of punchy writing, many important research results and underneath her advocacy style, some interesting questions about diet, exercise and other “Paleo” lifestyle features. However, my instinct is that many people won’t see these points due to Zuk’s approach, which will lead to a less interesting debate than we could have had. I suppose this post is further evidence of that.

*To avoid getting completely derailed by style instead of substance, next week I’ll write a post on what I consider to be the most interesting questions about recent evolution and the Paleo lifestyle (read it here).

Links this week:

1. Andrew Gelman critiques the recent paper on bicep size and political preferences.
2. Our food is evolving. John Hawks comments.
3. A nice article on growing evidence that a bit of extra weight later in life is not a bad thing.
4. If you’re not subscribed to the a replicated typo feed, get on it. More on memes.

While looking for something completely unrelated, I came across this 2007 Econ Journal Watch paper Model Building versus Theorizing: The Paucity of Theory in the Journal of Economic Theory. From the abstract:

We argue that a model may qualify as theory only if it purports to answer three questions: Theory of what?, Why should we care?, What merit in your explanation? We examine the 66 regular articles appearing in the 2004 issues of Journal of Economic Theory—“the leading journal in economic theory” —and apply the three requirements. … We find that 27 articles fail the first test (Theory of what?) and 58 articles fail at least one of the three requirements. Thus, 88 percent of the articles do not qualify as theory. … We contend that the journal’s claim to scientific status is doubtful, as well as the very title of the journal. A truer title would be, Journal of Economic Model Building. More generally, we challenge calling model building “theory.”

While I would be reluctant to get drawn into an argument about what is theory, Klein and Romero’s argument about the lack of relevance of much economic modelling is important. They go on to say:

All stakeholders should be concerned that scholarly prestige will be leveraged in a way that feeds mere scholasticism, rather than real contributions to science, learning, and culture. Even if scholastic arts did not distort thought and understanding, they certainly might divert them from the things that matter more. If JET—and many other outlets—consists mainly of crafts that lack integrity as explanation, it does not deserve much prestige within the enterprise we call economics. This article, then, speaks to all stakeholders — elected officials, taxpayers, tuition payers, donors, university administrators, faculty, students, and other citizens concerned about the character and content of economics. …

Our concern is to challenge the semantics that hold that every model is (or entails) theory. We maintain that scientific culture understands theory to entail requirements of importance and usefulness. Theory must serve real purposes of the science, thus, arguably meriting attention from the scientific community.

Of Klein and Romero’s three questions, I usually worry about the third. Economic models are often not tested and even less commonly discarded. Klein and Romero point to some evidence.

It is possible that other economists take published models and subsequently supply the commitment to empirical relevance necessary to graduate the models to theory (Hausman 1992, 273). Whether such graduation occurs is a question calling for further research, but investigations by Philip Coelho and James McClure (2005; 2007) suggest that few models graduate to theory. In one investigation, Coelho and McClure identify the JET articles published in 1980 and containing at least five lemmas. They find that there were 12 such articles. They then investigate the articles that cite those 12 papers. As of June 2006, there were 237 articles that cite the 12 JET articles. They report that of 237, only nine utilize data. Of the nine, only two articles attempt a direct empirical assessment of the model’s results, and zero render a judgment of “accept” or “reject.

I sometimes fear that a lot of the work integrating economics and evolutionary biology might fall at this hurdle (particularly the discarding bit), as there are more theorists than experimentalists in this area. But thankfully there is so much relevant empirical work being done in evolutionary biology, anthropology, experimental psychology and behavioural economics that it’s going to be hard to maintain a poor theory in this area without somebody pulling it apart.

Links this week:

1. Robert Kurzban reports on a very cool dictator game experiment. Do people only give money in experimental conditions?
2. Nicholas Gruen digs up a nice Alfred Marshall quote.
3. Peter Turchin calls on cultural group selection to explain the transition to farming. Or maybe it’s because “people like to own stuff“.
4. Noah Millman on Jason Richwine. And another take-down of the paper suggesting the Victorians were smarter than us.
5. The French fertility transition.

If nothing else, David Sloan Wilson is ambitious. He’s been pushing the multilevel selection wheelbarrow with not much support for close to forty years (although support seems to be growing in some circles). And over the last couple of years, he’s been increasingly promoting the idea of a evolution-centred “science of intentional change” that will allow us to change our behavioural and cultural practices. And as a simple step on the way there, all we have to do is conceptually unify the behavioural sciences.

This program for a science of intentional change is now sketched out in an article for Behavioral and Brain Sciences (in press), co-authored with Steven Hayes, Anthony Biglan and Dennis Embry. The interesting thing about BBS articles of this nature, as explained in a companion post by Wilson at Evolution: This View of Life, is that they are followed by commentary of peers, with submissions for commentary due by 28 May. Given some of the criticisms in the article, I hope that the right respondents will be flushed out.

On a first read, I’m not sold on the concept. At times it feels as though the authors are swiping at a paper tiger. Parts of the paper feel like evolutionary overreach (with evolution encompassing the four prongs of genetics, epigenetics, learning and symbolic thought), and I struggled to understand what evolution added to the understanding of many of the examples. And the discussion of group dynamics is laced with Wilson’s approach to multi-level selection, which raises questions about how informative the evolutionary approach is if you disagree with Wilson’s starting point.

Still, there are plenty of good and interesting ideas in the article and maybe I’ll be more on side after I give it some more thought and (hopefully) see some good critiques. In the meantime, here are some interesting passages (minus references):

[A]n enormous amount of integration must occur before a science of human behavioral and cultural change can center on evolution. This integration needs to be a two-way street, involving not only contributions of evolutionary theory to the human- related disciplines, but also the reverse. For example, core evolutionary theory needs to expand beyond genetics to include other inheritance systems, such as environmentally induced changes in gene expression (epigenetics), mechanisms of social learning found in many species, and the human capacity for symbolic thought that results in an almost unlimited variety of cognitive constructions, each motivating a suite of behaviors subject to selection.

We will argue that the first steps toward integration, represented by a configuration of ideas that most people associate with the term evolutionary psychology (EP), was only the beginning and in some ways led in the wrong direction. In particular, the distinction between EP and the standard social science model (SSSM) was a wrong turn we must correct. A mature EP needs to include elements of the SSSM associated with major thinkers such as Emile Durkheim, B.F. Skinner, and Clifford Geertz. Only when we depolarize the distinction between EP and the SSSM can a science of change occur.

Do evolutionists rely upon their own “blank slate” assumption”? I hope Steven Pinker takes the time to respond to this piece.

Ironically, although Tooby and Cosmides praised genetic evolution as a domain-general process, capable of adapting organisms to virtually any environment, they failed to generalize this insight to include other evolutionary processes. If they had, their critique of the “blank slate” traditions in the human behavioral sciences would have appeared in a new light.

Evolutionists routinely rely upon a “blank slate” assumption of their own when they reason about adaptation and natural selection. They predict the adaptations that would evolve by natural selection, given heritable variation and a sufficient number of generations. For example, they confidently predict that many species inhabiting desert environments will evolve to be sandy colored to conceal themselves from their predators and prey. This prediction can be made without any knowledge of the genes or physical composition of the species. Insofar as the physical makeup of organisms results in heritable variation, that is the extent to which it can be ignored in predicting the molding action of natural selection. The phenotypic properties of organisms are caused by selection and merely permitted by heritable variation.

Evolutionists have focused on only one evolutionary process, missing out on much of the power of the evolutionary approach.

Evolutionists do not have an already perfected framework to offer other disciplines. They have concentrated almost entirely on genetic evolution and paid scant attention to evolutionary processes that rely upon other mechanisms of inheritance. The dominant heuristic in narrow-school EP, when trying to explain a particular trait, is to assume that it is genetically determined, ask how it evolved by genetic evolution in the distant past, and then ask how it functions in the current environment. For traits associated with parental neglect, the heuristic has led to valid insights concerning the importance of such things as genetic relatedness or availability of resources. Yet it missed the fast-paced process of selection by consequences, resulting in behavioral strategies in parents and offspring that are adaptive in the context of the immediate family environment but profoundly maladaptive over the long term. These are the practices that are most amenable to change after identifying and understanding the contingencies. Evolutionists therefore have much to learn from branches of the human behavioral sciences where learning as a variation-and- selection process has occupied center stage for decades.

If only we consider all forms of evolution, seemingly insoluble problems may seem tractable.

A believer in Jesus sees the world differently than a follower of Ayn Rand, and seeing differently results in acting differently. This is true not only for religions and political ideologies, but also for scientific theories, as Tooby and Cosmides correctly note. Consider the possibility that severe personal and societal dysfunctions, which have defied solutions for decades, can sometimes be relieved by interventions that require just a handful of hours. Against the background of an evolutionary theory confined to genetic evolution, this claim seems too good to be true. Against the background of an evolutionary approach that actively manages a symbotype-phenotype relationship, the possibility begins to make more sense. If we expect artificial selection, genetic engineering, and gene therapy to provide new solutions, then why not expect the same from their counterparts in learning and symbolic systems? In this fashion, expanding core evolutionary theory beyond genetic evolution results in new possibilities for action that were previously invisible. Indeed, as the behavioral and symbolic impact on epigenetic processes becomes better understood, this expansion promises to alter our perspective on the role of genetic evolution itself.

If you have a bit of time up your sleeve, give the paper a read.