A week of links

Links this week:

  1. It’s from late last year, but this piece on the biological origins of morality is worth reading.
  2. A new journal, Economic Anthropology, with the debut issue on greed and excess (and sorry, gated for those without academic access).
  3. Diane Coyle points to some older work on wealth and inheritance. She also pointed me to this good interview with E.O Wilson.
  4. Another good bash of p-values.
  5. Who is buying the cigarettes? HT: Bryan Caplan
  6. Baby names. HT: Eric Crampton

And Kelly Slater’s winning “Wave of the Winter”:

A week of links

Again, closer to a month of links:

  1. A great set of essays triggered by David Dobbs’s assault on the selfish gene.
  2. Tim Harford on big data. His piece on behavioural economics is also worth reading. Take the hype with a grain of salt.
  3. The Greg Clark show continues – an interview on Social Science bites, a presentation at the RSA and some thoughts by Greg Cochran.
  4. Charles Murray has a new book on its way – The Curmudgeon’s Guide to Getting Ahead: Dos and Don’ts of Right Behavior, Tough Thinking, Clear Writing, and Living a Good Life
  5. A good long-read on de-extinction.
  6. Free-range kids.

A week of links

More like a month of links, but here goes:

  1. We’re going to be hearing a lot about Greg Clark’s new book on social mobility – The Son Also Rises: Surnames and the History of Social Mobility. Clark gives a synopsis in the NYT. In short, Clark and his colleagues estimate “that 50 to 60 percent of variation in overall status is determined by your lineage.”
  2. Kolk and colleagues present a paper in The Proceedings of the Royal Society B presents a model in which intergenerational fertility correlations drive a long-term fertility increase. They cite my working paper a source for genetic correlations driving fertility up. When (if) I get that paper published, do I now cite back?
  3. The germs made you do it. (A good long read)
  4. Are the hot hand deniers, so desperate to demonstrate cognitive biases, falling to biases of their own?
  5. Don’t hire like Google.
  6. Behavioural economics versus behavioural finance. On House’s question of where the behavioural economics folk are, I suggest the supply responded to the demand.

Cooperation and Conflict in the Family Conference wrap

Over the past year I have posted several times about the Cooperation and Conflict in the Family Conference, which was held in Sydney this week. It turned out to be a great conference, and I am very pleased with how it panned out.

The conference has increased my optimism about the potential for more work to be carried out at the inter-disciplinary boundaries between economics, evolutionary biology, anthropology, psychology and so on. When I compare it to the Social Decision Making: Bridging Economics and Biology conference I attended almost three years ago (an excellent conference), we managed to drag in a broader range of economists and other social scientists to this event. I suspect this is evidence for increasing interest on the part of social scientists in how sciences such as biology can add to the social science toolkit.

As a result, I hope this conference is the first of a continuing series (although hopefully with a wider group of organisers). An interesting challenge for the next iteration will be to pick an appropriate theme. In this case, the Cooperation and Conflict in the Family theme was useful in pulling together people who may not have necessarily considered that there were useful insights in other disciplines. We would not have gotten such an interesting mix of people if we had pitched the topic specifically around the integration of disciplines.

It was interesting to see the different presentation styles across disciplines, and I have to say that the biologists (on average) have the edge in presenting their work in an easy to understand way – particularly in relation to the submitted presentations. Us economists are still too tied to our equations to dump them. This was best illustrated in the presentations of two plenary speakers – Michael Jennions and Hanna Kokko – who used simple cartoons and illustrations to describe their models. If you go to their papers (particularly the supplementary materials), there can be some relatively hefty math behind them. Yet they are able to present the ideas without relying on the equations. And maybe this should also be taken as an indication for how economists write their papers – more of the math in the supplementary appendix, more time in the (shorter) main paper on the important intuition. And then dump the math when we intend to communicate our ideas verbally.

The conference also reminded me of how hard it is to work across disciplinary boundaries without full immersion in both sides (or having someone from both sides engaged in the work). Again turning the Michael Jennions presentation, he talked about Bateman’s gradient and the operational sex ratio, and about what each of them actually show (the paper on this is here). I thought I knew what each were about, but am now revisiting my understanding.

Finally, we recorded most of the plenary and submitted presentations and are exploring ways to make sure that the outputs of the conference do not disappear into the ether. When we do put some material together and post it online, I’ll put a note here and on the conference website.

A week of links

Links this week:

  1. Greg Clark on long-term social mobility.
  2. Cameron Murray on his reading list – Tribes, Gods, Indeterminancy, Property, Capitalism
  3. Assortative mating drives income inequality.
  4. The behavioural science of sleep.
  5. The Cooperation and Conflict in the Family Conference kicks off today. Rob Brooks posts. For Sydney folk, there are some free public lectures as part of the conference that will be worth checking out.

A change of blogging pace and style

Since late 2010, I have usually generated two or more substantive posts per week at Evolving Economics. Unfortunately, I’ve reached a point where I can’t sustain posting at the rate and quality I would like. The combination of writing my (near complete) PhD, trying to publish the chapters as papers, working full-time as a consultant (on a very interesting project for most of 2014), reading as much as I would like, and trying to have a life has proved a touch too much.

So, I’m changing my blogging strategy for the immediate future to a lower output approach. Posts will appear if I find time and mental space. I plan for some of those posts to be higher quality long reads – of the standard I’d be happy to see published in a magazine. I’ll also keep posting on my research and on events such as the upcoming Cooperation and Conflict in the Family Conference. But there will be no (self-imposed) schedule and some reasonably long gaps between substantive posts.

At the other end of the spectrum, I will keep putting up my “week of links” posts as a pointer to the interesting pieces I come across (although they may not arrive exactly on a weekly schedule). I may also post other quick notes of interesting articles and papers that I come across.

And I’m looking forward to it. During the last two months of 2013, posting was sporadic as I took a surfing holiday, came down with a fever that I picked up in the tropics, and took some time off over Christmas. I enjoyed the change of pace and the absence of a (completely self-imposed) obligation to generate regular content. I had more space for reading and getting across new ideas.

I may revert back to a more regular posting pattern if circumstances and resource constraints permit. But until then, thanks for the flow of comments, thoughts and support I’ve received over the last few years. I’m not disappearing, just being a little less productive on the blogging front.

And as has been the case for a while, if you would like to be notified of new posts when they do arrive, follow me on twitter or Google+ (there is also a Facebook page, although I’d recommend the other options first). You can also subscribe to posts via email by entering your address in the sidebar to the Evolving Economics page or in the box at the bottom of this post. There is also an RSS feed (if you still have a feedburner subscription to the feed, I recommend that you update your RSS feed to the one in the link above – that link will get you posts without delay and this feed address will persist if Google ever pulls the feedburner plug).

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A week of links

Links this week:

  1. A cool idea – people who are genealogical ancestors of everyone alive but genetic ancestors of none (HT: Joe Pickrell).
  2. Philip Ball on how the apparently irrational can be rational.
  3. John Kay on the economic approach – there is no such thing.
  4. Genetically modified chickens.
  5. The annual Edge question is out, this time “What Scientific Idea is Ready for Retirement?” Of those answers written about areas I am familiar with or interested in, the question has effectively been “What Scientific Idea Don’t You Like?” As a result, we get the latest play in old debates on race, IQ, the limits to growth (Ridley, Hidalgo and  Obrist), inclusive fitness, gene-environment interactions (Pinker and Sapolsky among others ), epigenetics, rationality, homo economicus and culture (Betzig, Richerson and Tooby). Some are framed in interesting ways (I like Sapolsky’s approach), but there are few surprises. I found more value in the answers that addressed approaches to science (such as Richard Thaler, Nicholas Christakis and Samuel Arbesman).
  6. And finally, surfing the US-Mexico border fence (HT: Michael Clemens).

The interplay of genetic and cultural evolution

In my last post, I discussed the framework for cultural evolution laid out by Claire El Mouden and colleagues in a new article in the Journal of Evolutionary Biology (ungated pdf and supporting information). By setting out clear definitions for the analysis of cultural evolution, such as cultural relatedness and fitness, a workable framework using evolutionary biology’s Price equation can be developed.

As I noted in that post, it is when the biological and genetic frameworks are laid on top of each other, as is the focus of the dual-inheritance literature, that things get interesting. With their framework, El Mouden and friends tackle a couple of the prominent gene-culture evolution questions.

The first question is to what extent cultural evolution increases or decreases genetic fitness. The authors note that a theme of the gene-culture evolution literature is that cultural evolution made the scale and distribution of today’s human population possible. How does this work?

For there to be a positive correlation between cultural and genetic fitness, those who have the most cultural influence must also leave the most offspring. It is easy to see circumstances where this holds, with those of high social status tending to have both cultural influence and more offspring (look at the number of partners of rock stars).

An example to the contrary is low fertility in developed countries. El Mouden and colleagues reference work by Richerson and Boyd, who suggest that high status is given to professions with high investment in education, which would allow the behaviour to spread despite the negative relationship between education and fertility.

However, El Mouden and friends show that this mismatch between cultural and genetic fitness is evolutionarily unstable as genetic natural selection acts to align genetic and cultural fitness. They suggest two reasons for this, one involving transmission and the other selection.

Their transmission explanation relies on the already evolved propensity for people to avoid behaviours that are harmful to their genetic interests. For example, the nausea produced when consuming toxins would fight against any cultural pressure to eat toxic food. However, it is an interesting question as to how general this transmission effect would be, as many cultural forces are novel and without precedent in our evolutionary history. Transmission may be unlikely to constrain our desire for high status professions that require large investments in education any time soon.

The genetic selection explanation would seem to have broader power. In the supplementary information, the authors ask us to consider a population where cultural and genetic fitness were not aligned. Now, imagine a mutant in that population that causes people to pay attention to a cultural trait that is more highly correlated with genetic fitness. As these mutants have higher genetic fitness, they increase in proportion of the population, and cultural and genetic fitness are now more correlated. Cultural fitness now promotes genetic fitness. In the long-run, the two will be perfectly correlated (the exception being where cultural traits are neutral to genetic fitness).

The catch in that last sentence is the “long-run”. As cultural evolution can be so much faster than genetic evolution, systems can be far from genetic equilibrium until the genetic response evolves. Fertility in developed countries would be an example of this. There may also be some constraints that prevent perfect alignment, such as the presence of appropriate learning mechanisms.

This interaction of genetic and cultural evolution gets most interesting is when we turn to the evolution of altruism. In examining this question we must remember that genetic and cultural fitness are distinct. Cultural altruism reduces the altruist’s cultural fitness; that is, their influence. As a result, the claim that cultural evolution increases genetic altruism (the more common claim in the gene-culture evolution literature) needs to be made carefully.

As an illustration, consider this interesting example from the paper. A stranger is being attacked, so a good Samaritan steps in to defend them and dies as a result. Whether this is culturally altruistic would depend on whether the Samaritan’s deed was copied. If so, then the Samaritan’s act would actually have been increase cultural fitness as it would have increased their influence in respect of that cultural trait.

Conversely, their death is genetically altruistic. As a result, genetic selection would tend to act against it. Those who ignore this cultural trait will have higher genetic fitness, grow in proportion of the population and eventually bring cultural and genetic fitness into alignment.

So what of behaviours that are both culturally and genetically altruistic? Whether the behaviour spreads will depend on the degree of cultural and genetic relatedness.

Evidence suggests that cultural relatedness within ethnic groups is higher than genetic relatedness (although it is still not high in absolute terms, with more within group than between group variation). This means that there are a wider range of circumstances for which cultural altruism can emerge than for genetic altruism. However, that domain in which cultural but not genetic altruism is likely to emerge will be subject to the forces described above to align cultural and genetic fitness.

Another important point is that each cultural trait should be considered separately. Even though a group may have the same language, giving them high relatedness for this cultural trait, this does not mean that they have the same views on giving their lives for strangers, for which they may have low cultural relatedness. Consideration of the conditions for altruism need to consider the specific cultural trait.

There are many other interesting points in the article – I recommend reading the whole thing – but I will close with a point on the practicality of modelling cultural evolution in this way. El Mouden and friends note that there is a host of complications not present in the genetic case. Cultural relatedness can vary wildly across cultural traits, whereas the nature of genetic transmission means that relatedness is similar across most of the genome. Recognising the pattern of inheritance is also a challenge, as ancestor numbers can vary in number and be of vastly different biological ages. In that context, there is no such thing as a standard length of generation.

So although this paper presents a nice approach to cultural evolution, it does not present an approach that is easily applied to empirical observation. However, given the lack of clarity across much of the gene-culture evolution literature, particularly when examined across authors and papers, it is nice to see an attempt to achieve some conceptual coherence.

Doing cultural evolution right

A sojourn into the literature on cultural evolution can be confusing. Authors use the same terms in different ways. Unique models are used to reach opposite conclusions. And each author seems to find their own way to intertwine genetic evolution into the analysis.

In that light, a new article in the Journal of Evolutionary Biology (ungated pdf and supporting information) by Claire El Mouden and friends seeks to nail down some of the concepts of cultural evolution and to set up a general framework (thank you!). The paper is at a more basic level than that of Geoffrey Hodgson and Thorbjørn Knudsen’s book Darwin’s Conjecture, which also sought to define and generalise concepts in this area.

El Mouden and her colleagues’ paper covers a lot of interesting terrain, so I will cover it in two posts. In the first, I’ll cover the basics of a cultural evolution framework. In the second, I will look at how cultural and genetic evolution interact in this framework.

The authors set up their framework using the Price equation from evolutionary biology. The Price equation divides evolutionary change of a trait into two components. The first is a natural selection component resulting from the covariance between a trait and relative fitness. Where there is large covariance, evolution will be fast. Second is a transmission component, which is the fitness-weighted change in trait value between generations (for example, increasing height with improved nutrition across the population would be considered transmission). The Price equation has the neat property that it can be decomposed into within-group and between-group components, allowing analysis in a multilevel selection framework (although not everyone is happy with this decomposition).

But to use this framework, it is important to clarify some terms (which is one of my bugbears about the cultural evolution literature). First, relatedness. As the units of inheritance are cultural traits, the measure of relatedness is similarity in cultural traits. In a simple model where we have one cultural trait, anyone with that same cultural trait has a relatedness of one. In effect, when passing on a cultural trait to another person, they become kin.

The use of the term relatedness is often confusing in the cultural evolution literature as the relatedness of interest is typically genetic relatedness. That is fine, but we need to distinguish the two types of relatedness. Cultural kin are not necessarily genetic kin.

Second, fitness. Cultural fitness reflects the number of people who learn from an individual, plus the degree of influence that they have on those people. Degree of influence is important because, unlike genetic evolution where you have a known and fixed number of ancestors (one parent in the case of asexually reproducing species, two parents for sexually reproducing species such as humans) who contribute a specific amount of genetic material, the number of cultural ancestors may vary by trait and between people. How many people have influenced your cooking? Who was more influential?

Further, for each cultural trait, people will have different fitness. The authors offer the example of Beethoven, whose influence in cookery did not match his influence in music. This necessitates different measurements of cultural fitness for different traits.

Third, generation. The ancestor-descendent relationship is defined by influence, and can have weak relation to biological age. Plato is still spawning direct cultural descendants today, whereas ideas can also spread through a population in days. However, it is only possible to influence people in the next cultural generation, as that is how generation is defined. If I influence someone, they are the next cultural generation in respect of that cultural trait.

Having defined these concepts, they are relatively easy to slot into a cultural Price equation (the maths is in the supplementary information to the paper). While there is extra complexity from considering the degree of influence rather than just the number of descendants, the form of the Price equation is effectively the same for both the genetic and cultural forms. It is just that each deals distinctly with genetic or cultural fitness.

It is also possible to derive a Cultural Hamilton’s Rule. In biology, Hamilton’s rule states that a gene will spread if the cost of the act to the altruist is less than the benefit accrued by the beneficiaries adjusted by the degree of relatedness. A gene can spread if you help kin who also have that gene, even if it comes to a cost to yourself.

Similarly, the Cultural Hamilton’s Rule states that “a behaviour that reduces the actor’s lifetime cultural influence can only be culturally selected for if the cost to him is less than the product of the cultural benefit to his interaction partners and their cultural relatedness to him”. On this point, the authors give an example of two philosophers with the same cultural views. If one chooses to farm to feed the other, allowing the other to focus on spreading the philosophy, the cultural trait may spread despite one of the philosophers effectively sacrificing his own influence.

Under this definition, cultural kin selection becomes a relatively parsimonious explanation for the spread of many cultural traits, such as altruism (and as noted above, this could also be converted into a multilevel selection framework). If people believe in altruism and help others who also do (who are their kin), then helping each other could assist in the further spread of the cultural trait of altruism.

However, this story of spreading cultural altruism falls somewhat short of covering the examples in much of the gene-culture evolution literature. The issue is that, while culture is a part of the model and analysis, people are typically interested in genetic altruism.

Thus, the question of interest is how cultural evolution affects the evolution of genetic altruism? That will be the subject of my next post.

A week of links

Links this week:

  1. Robert Kurzban wonders why priming works.
  2. A disturbing way of maximising fitness. A fertility clinic worker may be the father of a lot of children.
  3. Some chaff in with the wheat, but this article on Social Darwinism reports some interesting research.
  4. The program and accepted abstracts are up at the Cooperation and Conflict in the Family Conference website. Together with the invited speakers, it’s a great looking lineup.
  5. The Santa Fe Institute’s MOOC Introduction to Dynamical Systems and Chaos has kicked off.
  6. A new paper in JEBO. People cooperate because they are selfish. (ungated pdf)
  7. The world is complicated.

And to close, my twitter and blog feeds contain an inordinate amount of baseball content. I don’t understand why economists are so interested in baseball, despite the fact they can use their statistical skills to re-live the jock versus nerd battles of their childhood (In the same way, I don’t understand my countrymen’s infatuation with cricket – adults chasing balls?). Surely there are more interesting statistics.

So, to get some real sport into your feeds (this being the only sport in which I can bring myself to watch), I’m introducing a semi-regular surf link or clip to my week of links posts. Today, some awesome Pipeline footage (using drones, another area that economists seem to be infatuated with). I love how you can see the reef, the holes in it, and how the water depth changes so suddenly at its edge. Other highlights – Kelly Slater at 1:05 catching the wave that won him the recent Pipe Masters, and the crowd all paddling for the horizon at 2:54 when they see some sets starting to rear up on third reef. (As an aside, surfing could use some numerate economists – from the almost award of the Eddie Aikau to Tony Ray to the premature crowning of Kelly Slater as world champion, the surfing hierarchy could benefit from the ability to add.)