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April 17, 2017

Evolutionary game theory and international relations

Filed under: Behavioral Ecology,North Korea — Razib Khan @ 11:38 am

The North Korea Paradox: Why There Are No Good Options:

Denny Roy, a political scientist who studies Asian security issues, told me last fall that North Korea “intentionally employs a posture of seemingly hyper-risk acceptance and willingness to go to war as a means of trying to intimidate its adversaries.”

This puts the world in a quandary: How could any outside threat possibly exceed the risk that North Korea already takes on itself? How could any concession remove the North Korean weakness that drives its behavior?

Basically North Korea is a weak state. Its only leverage is to hold the world hostage and act crazy. Unfortunate, but true.

But this piece reminded me a lot of stuff that John Maynard Smith described in Animal Signals. Sometimes it is the weaker and more vulnerable animals which have to engage in high risk agonistic competition, so that they can show more fit individuals that there is going to be a significant cost in initiating hostilities.

It also reminds me of high school. If you are smaller than average, it is best to make it clear to larger bullies that you won’t be passive. You may lose the fight, but by escalating rapidly you can dissuade a bully from targeting you, as opposed to someone who is more likely to be an easier victim.

Of course, bullies need to be “rational” actors here….

April 16, 2017

In a hopeless world hope is better than resignation

Filed under: Economics,Economy — Razib Khan @ 11:59 pm

There’s really nothing one can say anymore about what Hugo Chavez did to his country, No Food, No Medicine, No Respite: A Starving Boy’s Death in Venezuela. But now in France a left-wing politician is on the rise who praises Chavez, Left-Wing Politician Shakes Up France’s Presidential Race:

That man is Jean-Luc Mélenchon, admirer of Fidel Castro and Hugo Chávez, sworn enemy of NATO and high finance, and candidate of his own “France Unsubjugated” movement, who has been drawing tens of thousands to his rallies, especially the young, as he did here Sunday at Toulouse on the banks of the Garonne River. They came to hear a veteran French politician give them a dousing of old-fashioned Robin Hood-revolutionary rhetoric, with promises to tax the rich hard, give to the poor and start a “citizen revolution.”

There is a serious chance that this will be the next president of the French republic. This man, who has no problems being called a Communist. If there is one political system where the experiment has been done, it is command economy socialism. There may be cases of market failure where the state needs to intervene, but by and large an economy dominated by the state has not done good for the common man.

And yet the reality is what alternatives are the people being given? They are looking Left and looking Right, because they want hope that the future will have some of the promise that the past had. Sober realistic centrists with broadly liberal views only offer them only hard truths.

Truths such as this: Evidence That Robots Are Winning the Race for American Jobs. The far Left anti-capitalist program in economics really doesn’t offer a long run path to prosperity. But capitalism itself only leads to individual and broad-based prosperity as a side effect of market logic. If returns to capital could accrue without labor inputs, then that would be even “better.”

The Warlord Chronicles

Filed under: Books — Razib Khan @ 11:42 pm

The Winter is Coming website has a post up, What books should you read as you wait for The Winds of Winter? (The Winds of Winter is the next Song of Ice and Fire book).

I don’t have much time for fiction at this point, but the first entry that they suggested was Bernard Cornwell’s Warlord Chronicles. This is a very dark, gritty, and realistic, retelling of the Arthurian legend, written in a fashion more reminiscent of historical fiction than fantasy. I read this series perhaps a year after first reading Game of Thrones, and was struck by similarities of tone.

As it happened this was before George R. R. Martin was quite as famous, and I emailed him at some point in 2000 about various issues relating to his works and inspirations, and asked him about Cornwell’s series. Martin admitted that he was a huge fan, and appreciated that there were similarities of style and tone.

In any case, I second this recommendation. Warlord Chronicles is not the most easy read…but worth it.

Open Thread, 4/16/2017

Filed under: Blog,Open Thread — Razib Khan @ 4:41 pm

Happy Easter. Spend most of the day figuring out how to restart Varnish. I don’t really know why there are so many database connection problems and caching…but I inherited the VPS. Might have to bone up on being a sysadmin more. Do any readers know if Varnish is really worth a modest site like mine?

Erdogan Claims Vast New Powers After Narrow Victory in Turkish Referendum. First, I have to say that The Future of Freedom: Illiberal Democracy at Home and Abroad is pretty relevant today. Second, Erdogan has shown many faces to the world over the past 15 years. I remember for example him telling people in post-Arab Spring Tunisia that in a free society atheism is a real option (to some criticism).

Are 90% of academic papers really never cited? Reviewing the literature on academic citations. It’s really a problem in the humanities:

Many academic articles are never cited, although I could not find any study with a result as high as 90%. Non-citation rates vary enormously by field. “Only” 12% of medicine articles are not cited, compared to about 82% (!) for the humanities. It’s 27% for natural sciences and 32% for social sciences (cite). For everything except humanities, those numbers are far from 90% but they are still high: One third of social science articles go uncited! Ten points for academia’s critics. Before we slash humanities departments, though, remember that much of their most prestigious research is published in books. On the other hand, at least in literature, many books are rarely cited too.

White supremacist who created stir at Stanislaus State seen punching woman at Berkeley protest. First, please note that this woman went to the protest to get “Nazi scalps” according to her social media. Second, the image of a white supremacist punching an anti-fascist woman is exactly what Sarah Haider told me was going to be a problem with contemporary Leftist valorization of violence: Left-wing organizations have proportionally many more women than right-wing militant organizations, which isn’t an asset in pitched physical combat.

Theresa May’s Conservatives are 21 points ahead of Labour in new poll. I think Scotland will leave the United Kingdom in the next 5 years.

Suzan Mazur interviews Richard Lewontin. I used to think Mazur was exceptional, and she still is, but only in her artlessness in pushing her agenda.

Treasure your exceptions, progress is real but not universal

Filed under: Apostasy,Atheist,Culture — Razib Khan @ 12:41 am

The beginning of How the Scots Invented the Modern World describes the execution of a man for the crime of atheism around 1700 in Scotland. More precisely, this individual was rather loud about their heresy, and that is always the problem. Silent dissent is usually tolerated. This is the last time someone was executed for this particular crime in the British Isles.

In the United Kingdom the book was more accurately titled The Scottish Enlightenment. A relatively moderate and low fuss affair, the Scottish Enlightenment gave us Adam Smith and David Hume, to name two. The point of the book is that in it one can see many of the seeds of the liberal Enlightenment more broadly in Scotland, while in the beginning of the 18th century was arguably more backward and medieval than its southern neighbor.

But the “modern world” means many different things. Mobile phone technology is ubiquitous, to the point that even the poor in developing nations have it. But a broader consumer affluence is out of reach for many. And the rights and liberties of a liberal democratic order are more an ideal than concrete existence for much of the world’s population (and you have cases such as Saudi Arabia where illiberal norms and politics merge with consumer affluence).

As you may know a young man was killed by his fellow students in Pakistan for the crime of blasphemy a few days ago. Whether he was an atheist or a free thinker, or a skeptic more generally, can be hard to ascertain. But the critical aspect is that he was killed in broad daylight by a mob. He was lynched. This being 2017, you can watch a video of the killing, and hear his screams as he is murdered in front of a crowd.

One aspect people have been noticing is that this was a killing enabled by majority and consensus opinion. Abdul Wali Khan University Mardan is a public university, not a cloistered madrassa or a branch of the Red Mosque network. You can’t blame ISIS or some crazy jihadi network. These were university students.

Pakistan has a population of 182 million. The United States around 300 million. I understand that Americans believe we are the future. That the rest of the world is the exception. But how long will that be? Perhaps the arrow of history is more a circle?

April 15, 2017

Genetic variation in human populations and individuals

Filed under: Genetics,Genomics,Human Genetics,Polymorphisms,SNPs — Razib Khan @ 9:25 pm

I’m old enough to remember when we didn’t have a good sense of how many genes humans had. I vaguely recall numbers around 100,000 at first, which in hindsight seems rather like a round and large number. A guess. Then it went to 40,000 in the early 2000s and then further until it converged to some number just below 20,000.

But perhaps more fascinating is that we have a much better catalog of the variation across the whole human genome now. Often friends ask me questions of the form: “so DTC genomic company X has about 800,000 SNPs, is that enough to do much?” To answer such a question you need some basic numbers in your head, as well as what you want to “do.”

First, the human genome has about 3 billion base pairs (3 Gb). That’s a lot. But most of the genome famously doesn’t code for proteins. The exome, the proportion of the genome where bases directly translate into a protein accounts for 1% of the whole genome. That’s 30 million bases (30 Mb). But this small region of the genome is very important, as the vast majority of major disease mutations are found in the exome.

When it comes to a standard 800K SNP chip, which samples 800,000 positions across the 3 Gb genome, it is likely that the designers enriched the marker set for functional positions relevant to diseases. Not all marker positions are created equal. Though even outside of those functional positions there are often nearby SNPs that can “tag” them, so you can infer one from the state of the other.

But are 800,000 positions enough to make good ancestry inference? (to give one example) Yes. 800,000 is actually a substantial proportion of the polymorphism in any given genome. There have been some papers which improved on the numbers in 2015’s A global reference for human genetic variation, but it’s still a good comprehensive review to get an order-of-magnitude sense. The table below gives you a sense of individual variation:

Median autosomal variant sites per genome

When it comes to single nucleotide polymorphisms (SNPs), what SNP chips are getting at, an 800K array should get a substantial proportion of your genome-wide variation. More than enough for ancestry inference or forensics. The singleton column shows mutations specific to the individual.  When focusing on new mutations specific to an individual that might cause disease, singleton large deletions and nonsynonymous SNPs is really where I’d look.

But what about whole populations? The plot to the left shows the count of variants as a function of alternative allele frequency. When we say “SNP”, you really mean variants which exhibit polymorphism at a particular cut-off frequency for the minor allele (often 1%). It is clear that as the minor allele frequency increases in relation to the human reference genome the number of variants decreases.

From the paper:

The majority of variants in the data set are rare: ~64 million autosomal variants have a frequency <0.5%, ~12 million have a frequency between 0.5% and 5%, and only ~8 million have a frequency >5% (Extended Data Fig. 3a). Nevertheless, the majority of variants observed in a single genome are common: just 40,000 to 200,000 of the variants in a typical genome (1–4%) have a frequency <0.5% (Fig. 1c and Extended Data Fig. 3b). As such, we estimate that improved rare variant discovery by deep sequencing our entire sample would at least double the total number of variants in our sample but increase the number of variants in a typical genome by only ~20,000 to 60,000.

An 800K SNP chip will be biased toward the 8 million or so variants with a frequency of 5%. This number gives you a sense of the limited scope of variation in the human genome. 0.27% of the genome captures a lot of the polymorphism.

Citation: 1000 Genomes Project Consortium. “A global reference for human genetic variation.” Nature 526.7571 (2015): 68-74.

April 14, 2017

Why overdominance probably isn’t responsible for much polymorphism

Filed under: Genetics,Population genetics — Razib Khan @ 10:54 pm

Hybrid vigor is a concept that many people have heard of, because it is very useful in agricultural genetics, and makes some intuitive sense. Unfortunately it often gets deployed in a variety of contexts, and its applicability is often overestimated. For example, many people seem to think (from personal communication) that it may somehow be responsible for the genetic variation around us.

This is just not so. As you may know each human carries tens of millions of genetic variants within their genome. Populations have various levels of polymorphism at particular positions in the genome. How’d they get there? In the early days of population genetics there were two broad schools, the “balance” and “classical.” The former made the case for the importance of balancing selection in maintaining variation. The latter suggested that the variation we see around us is simply a transient between fixation of a favored mutation from a low a frequency or extinction of a disfavored variant (perhaps environmental conditions changed and a high frequency variant is now disfavored). Arguably the rise of neutral theory and empirical results from molecular evolution supported the classical model more than the balance framework (at least this was Richard Lewontin’s argument, and I follow his logic here).

But even in relation to alleles which are maintained at polymorphism through balancing selection, overdominance isn’t going to be the major player.

Sickle cell disease is a classic consequence of overdominance; the heterozygote is more fit than the wild type or the recessive disease which is caused by homozygotes of the mutation. Obviously polymorphism is maintained despite the decreased fitness of the mutant homozygote because the heterozygote is so much more fit than the wild type. The final proportion of the alleles segregating in the population will be conditional on the fitness drag of the homozygote in the mutant type, because as per HWE it will be present in the population ~q2.

The problem is that this is clearly not going to scale across loci. That is, even if the fitness drag is more minimal than is the case with the sickle cell locus, one can imagine a cummulative situation. The segregation load is just going to be too high. Overdominance is probably a transient strategy which fades away as populations evolve more efficient ways to adapt that doesn’t have such a fitness load.

So how does balancing selection still lead to variation without heteroygote advantage? W. D. Hamilton argued that much of it was due to negative frequency dependent selection. Co-evolution with pathogens is the best case of this. As strategies get common pathogens adapt, so rare strategies encoded by rare alleles gain in fitness. As these alleles increase in frequency their fitness decreases due to pathogen resistance. Their frequency declines, and eventually the pathogens lose the ability to resist it, and its frequency increases again.

What if you call for a revolution and no one revolts?

Filed under: EES,Evolution,Genetics,Neo-Darwinian Synthesis — Razib Khan @ 3:30 pm

When I was in 8th grade my earth science teacher explained he did not believe in Darwinism. He seemed a reasonable fellow so my first reaction was shock. My best friend at the time, who sat next to me, laughed, “Yeah, some people believe we’re descended from monkeys! Crazy, huh?” I didn’t really know what to say. But what followed was even more confusing to me: my teacher explained that he accepted punctuated equilibrium, not Darwinism. He did not elaborate much beyond this, though I tried to get at what he believed after class in the few minutes I had.

Later on I realized that he had drunk deeply at the well of Stephen Jay Gould, paleontologist and polymath. I will quote Richard Lewontin, Gould’s longtime collaborator and friend:

Now I should warn you about my prejudices. Steve and I taught evolution together for years and in a sense we struggled in class constantly because Steve, in my view, was preoccupied with the desire to be considered a very original and great evolutionary theorist. So he would exaggerate and even caricature certain features, which are true but not the way you want to present them. For example, punctuated equilibrium, one of his favorites. He would go to the blackboard and show a trait rising gradually and then becoming completely flat for a while with no change at all, and then rising quickly and then completely flat, etc. which is a kind of caricature of the fact that there is variability in the evolution of traits, sometimes faster and sometimes slower, but which he made into punctuated equilibrium literally. Then I would have to get up in class and say “Don’t take this caricature too seriously. It really looks like this…” and I would make some more gradual variable rates. Steve and I had that kind of struggle constantly. He would fasten on a particular interesting aspect of the evolutionary process and then make it into a kind of rigid, almost vacuous rule, because—now I have to say that this is my view—I have no demonstration of it—that Steve was really preoccupied by becoming a famous evolutionist.

Gould succeed, after a fashion. His reputation within evolutionary biology is mixed, at best. Just look at what someone who thinks he made genuine original contributions to science admits above. But in the mind of the public Stephen Jay Gould was an oracle of sorts.

A revolution is sexy. A revolution sells. Having read both of them, I would say that Richard Dawkins is the better stylist when compared to Gould. Additionally, though some might disagree with this Dawkins is closer to the mainline of the modern evolutionary biological tradition than Gould. But in the United States Gould far overshadowed Dawkins…until the latter began to make a name for himself as an anti-religion polemicist in the 2000s. Revolution. Controversy. They’re salient. The press eats it up, and the public trusts the press.

And some things never change. Every few years there is an impending “revolution” in evolutionary biology or genetics. But the revolution is mostly in the minds of a few journalists, and a public that reads a little too much into a puff piece here and there. The sort of well educated public woolly on what the “central dogma” is, but clear that it has been overthrown.

Sometimes this gets out of control. Suzan Mazur’s The Altenberg 16: An Exposé of the Evolution Industry is probably the weirdest instance of this genre of “the sky is falling in evolutionary theory!” But of late some scholars have been coming out with more sober critiques, arguing that the Neo-Darwinian Synthesis needs to be extended or modified significantly. Kevin Laland’s Darwin’s Unfinished Symphony: How Culture Made the Human Mind is the latest instance of this, but you can also read Evolution in Four Dimensions: Genetic, Epigenetic, Behavioral, and Symbolic Variation in the History of Life. You can also read David Dobbs’ sympathetic treatment from a few years back around this issue.

I can communicate to you what seems to be the majority view among the evolutionary biologist I know: there isn’t a need for a revolution in conceptual thought, just a working out of details and reallocation of resources. Many who are sympathetic to Kevin Laland’s argument still believe that it’s about emphases and semantics. There’s no reason to put out a clarion call that evolution needs to be rethought in its conceptual foundations.

Honestly I don’t know if there’s been much that is revolutionary since he original period of the synthesis. Perhaps the rise of molecular evolution and neutrality as a null hypothesis? But even I’m not sure about that.

Erik I. Svensson has put up a preprint which speaks for many people, On reciprocal causation in the evolutionary process. Read the whole thing, it’s thorough, and accessible to a lay audience. The main thing that is a bit surprising is the good work put in for The Dialectical Biologist, which I have heard is an interesting book:

Recent calls for a revision the standard evolutionary theory (ST) are based on arguments about the reciprocal causation of evolutionary phenomena. Reciprocal causation means that cause-effect relationships are obscured, as a cause could later become an effect and vice versa. Such dynamic cause-effect relationships raises questions about the distinction between proximate and ultimate causes, as originally formulated by Ernst Mayr. They have also motivated some biologists and philosophers to argue for an Extended Evolutionary Synthesis (EES). Such an EES will supposedly replace the Modern Synthesis (MS), with its claimed focus on unidirectional causation. I critically examine this conjecture by the proponents of the EES, and conclude, on the contrary, that reciprocal causation has long been recognized as important in ST and in the MS tradition. Numerous empirical examples of reciprocal causation in the form of positive and negative feedbacks now exists from both natural and laboratory systems. Reciprocal causation has been explicitly incorporated in mathematical models of coevolutionary arms races, frequency-dependent selection and sexual selection. Such feedbacks were already recognized by Richard Levins and Richard Lewontin, long before the call for an EES and the associated concept of niche construction. Reciprocal causation and feedbacks is therefore one of the few contributions of dialectical thinking and Marxist philosophy in evolutionary theory, and should be recognized as such. While reciprocal causation have helped us to understand many evolutionary processes, I caution against its extension to heredity and directed development if such an extension involves futile attempts to restore Lamarckian or soft inheritance.

Modernity is not magic with Muslims

Filed under: Culture,Islam,Religion — Razib Khan @ 10:06 am

There are many reasons I have become very skeptical of the media over the years. Though I do not subscribe to the conspiracy theory paradigms, it is obvious that the mainstream media often combines fidelity to precise narratives with a lack of detailed knowledge about the topics they are covering. In other words, they’re stenographers with an agenda. When you don’t know the topic they are expositing upon they can seem quite persuasive. But when you do know the topic they are addressing the emperor can be revealed to be naked. Naturally this warrants concern in most people who observe this, as if they are catching errors in the matrix.*

One area that this problem crops often for me is in regards to media coverage of Islam and and the Middle East. Most reporters don’t seem to really know much about their beat in a deep sense, so they are superficially taking in facts and putting them through coarse interpretative filters.

To name names, David Kirkpatrick covers the Middle East for The New York Times. I read his stuff, and he is not a bad journalist, but he clearly has no deep familiarity with the history of the Middle East to the details of Islam. His work is like a pop-tart; sweet, temporarily filling, but long on a sugar-rush and short on robustness substance. For example, he can talk about a contrast between peaceful Sufis and Islamist militants Libya, without knowing that Sufi orders were often militant organizations, and that Libyan independence after World War II was spearheaded by a militant Sufi order.

But readers of The New York Times “know” that Sufis are peaceful. So for prose contrast it makes sense that Kirkpatrick would bring that up. Never mind that this is so reductive to be useless in terms of getting people a better picture of reality.

In the interests of adding context, let me add something to the story about FGM in Michigan. A Dr. Jumana Nagarwala is accused of practicing FGM on young girls. Though it is not emphasized in the American media (because it wouldn’t mean much), it seems she is from the Dawoodi Bohra of Ismailis. In India the Bohra community is well known, as it is a very distinct group from the majority of Muslims, who are Sunni, and even most Shia. Its origins seem to be among the mercantile castes of the Gujarat coast.

I have some “book learning” about this sect under my belt because I read Mullahs on the Mainframe: Islam and Modernity among the Daudi Bohras about 15 years ago on the recommendation of my friend Aziz Poonawalla, who is a member of this community. Mullahs on the Mainframe was topical in the post-9/11 era because it seemed to depict a community which was both modern and religiously orthodox and observant, with fewer tensions being a minority in the West than other groups of Muslims. I don’t want to rehash that line of argument too much; descriptively it is correct that Daudi Bohras are a well behaved minority who attain success, combined with adherence to traditional beliefs and practices (Daudi Bohras, like many conservative Islamists, tend to “look” obviously Muslim because of matters of grooming and dress).

But another aspect of the Daudi Bohra community is that it is one of the few in South Asia that practices FGM. I don’t know or care about the prevalence, extent, or origin of the practice. When I saw the doctors name, which seemed South Asian, I immediately suspected she was from the community (the type of headscarf seemed familiar too).

The point of this post is not to demonize the Daudi Bohra community; the vast majority of the worlds Muslims who engage in FGM are not Daudi Bohra. The Shafi school of Sunni Islamic jurisprudence is the big offender in terms of numbers. Indonesian Sunnis are Shafi, so that nation often praised for its tolerant version of Islam, has a very high proportion of FGM. Rather, it is to point out that the neat narrative frameworks we prefer are often not descriptively correct nor predictively useful. Since 9/11 rather than a more complex and nuanced view of Islam it seems that opinion leaders have been converging upon the idea that the religion is either with the angels or the devils, rather than a man-made thing which occupies the area in the middle.

The reliance on theories and heuristics which appeal to our sensibilities as right and true misleads in many ways. The arc of history bends toward justice, but the path is winding. The Protestant Reformation was rooted in large part on the more literate and well off classes, and aimed to rid corruption from the Christian church. In the process it unleashed horrible intolerance, cultural genocide, and conflicts which resulted in tens of millions of deaths. Not taking a view on the Reformation as a whole, it is clear that its consequences are not so simply integrated into the Whig version of history when taken in full.

Ultimately we need to rush less quickly toward our preferred conclusions, which align neatly with our prior models. Rather, we need to explore the sideways and what we think are certainly dead-ends, because sometimes those dead-ends will open up startling new landscapes (by the way, I think the “rationalist” community is much better at this than the general thinking public, though that’s not saying much).

* When I was in grad school an acquaintance mentioned this in relation to Jonah Lehrer before his exposure. Lehrer was persuasive whenever he was talking about a topic he wasn’t familiar with, but was clearly out of his depth whenever it approached something he was familiar with.

The origin of organismic gangs

Filed under: Evolution,Game Theory — Razib Khan @ 12:55 am

When W. D. Hamilton was a student he expressed an interest in exploring the problem of altruism in an evolutionary context. His struggles in getting anyone interested in the issue and supporting his study of the topic is extensively detailed in Narrow Roads of Gene Land. But he persevered and for his efforts he came up with the framework of inclusive fitness (John Maynard Smith’s term was kin selection). To a great extent it was a revolutionary model, formalizing what he been roughly understood verbally.

But could inclusive fitness explain the social structure we see around us? Hamilton attempted to extend the framework to humans in the 1970s, but that was not particularly fruitful. Other dynamics which emerged on the scene drew more from game theory. Again, John Maynard Smith loomed large, but Robert Trivers also introduced reciprocal altruism into the lexicon. These sorts of processes were much favored by thinkers such as Richard Dawkins because they are simple elementary strategies and relations that are tractable, and can be programmed dand simulated (or analytically explored).

Other researchers have different ideas and appeal to alternative traditions. David Sloan Wilson, along with E. O. Wilson, have been trying to revive models predicated on higher levels of organization. Though often termed “group selection,” the first Wilson correctly labels it “multi-level selection theory.” Though I am willing to agree that the pendulum swung too far in favor of individual level game theory and inclusive fitness in the last few decades, I do find David Sloan Wilson’s triumphalism a bit much (though his books are worth reading, and I think this is a personality issue with David, as he engages in the same triumphalism with economists).

A lot of work still needs to be done to explain social organization and behavior, even in social insects! With that, two preprints in biorxiv caught my attention.

First, Co-evolution of dispersal with behaviour favours social polymorphism. In it the authors model a system where there are dispersing individuals and sessile individuals, and show that cooperative behavior and the sessile morph and selfish behavior and the dispersing morph can persist as two alternative strategies. The paper makes the assumption that the sets of behaviors are caused by different genes which are linked, and show that low recombination is necessary to maintain the linkage. This does not seem genetically realistic.

The second paper is of a broader purview, Stags, hawks, and doves: Social evolution theory and individual variation in cooperation:

One of the triumphs of evolutionary biology is the discovery of robust mechanisms that promote the evolution of cooperative behaviors even when those behaviors reduce the fertility or survival of cooperators. Though these mechanisms, kin selection, reciprocity, and nonlinear payoffs to cooperation, have been extensively studied separately, investigating their joint effect on the evolution of cooperation has been more difficult. Moreover, how these mechanisms shape variation in cooperation is not well known. Such variation is crucial for understanding the evolution of behavioral syndromes and animal personality. Here, I use the tools of kin selection theory and evolutionary game theory to build a framework that integrates these mechanisms for pairwise social interactions. Using relatedness as a measure of the strength of kin selection, responsiveness as a measure of reciprocity, and synergy as a measure of payoff nonlinearity, I show how different combinations of these three parameters produce directional selection for or against cooperation or variation in levels of cooperation via balancing or diversifying selection. Moreover, each of these outcomes maps uniquely to one of four classic games from evolutionary game theory, which means that modulating relatedness, responsiveness, and synergy effectively transforms the payoff matrix from one the evolutionary game to another. Assuming that cooperation exacts a fertility cost on cooperators and provides a fertility benefit to social partners, a prisoner’s dilemma game and directional selection against cooperation occur when relatedness and responsiveness are low and synergy is not too positive. Enough positive synergy in these conditions generates a stag-hunt game and diversifying selection. High levels of relatedness or responsiveness turn cooperation from a fitness cost into a fitness benefit, which produces a mutualism game and directional selection for cooperation when synergy is not too negative. Sufficiently negative synergy in this case creates a hawk-dove game and balancing selection for cooperation. I extend the results with relatedness and synergy to larger social groups and show that how group size changes the effect of relatedness and synergy on selection for cooperation depends on how the per capita benefit of cooperation changes with group size. Together, these results provide a general framework with which to generate comparative predictions that can be tested using quantitative genetic techniques and experimental techniques that manipulate investment in cooperation. These predictions will help us understand both interspecific variation in cooperation as well as within-population and within-group variation in cooperation related to behavioral syndromes.

I haven’t dug into the formal models in the methods sections of either preprint, so I won’t say much more. But, I will offer that as someone who has long been interested in this field there is a surfeit and not enough data to test the models. It is time for someone ambitious to figure out how to make these areas more empirically testable.

April 13, 2017

The revenge of the cavemen

Filed under: Anthroplogy,History — Razib Khan @ 5:08 pm

In 2012 I wrote Post-Neolithic revenge of the foragers. There were two proximate rationales for my thoughts at the time. First, I thought Peter Bellwood’s thesis of agricultural based demographic expansions in First Farmers was being vindicated in the broadest sketch, but there were many countervailing details. Second, there were already suggestions that genetic data was not indicative of a final victory of farmers by pastoralists.

There were several immediate issues that came to mind in the non-genetic domain. Bellwood argued that agriculture shape the distribution of modern language families, but the spread of Turkic and Finnic peoples seem likely to have been post-agricultural, and not based on farming. Both these groups were arguably nomadic, one pastoralist, and the other engaging in mixed use lifestyles which were reminiscent of classic hunting and gathering. And, there has been anthropological evidence that though pure hunter-gatherers, such as indigenous Australians, do not take to cultivation easily, they quickly transition to pastoralism. In other words, the skills and mores which are common among hunter-gatherers can translate rapidly once domesticate based nomadism spreads.

The Turks, or the Saami with their reindeer, are evidence of this transition, and its success. It seems plausible that the same was the case with Indo-Europeans, and that is what I thought at the time.

Now we have more data from ancient DNA. It does seem there was a “resurgence” of Mesolithic hunter-gatherer ancestry as time passed, with Neolithic farmers exhibiting a more indigenous genetic profile in Europe. Additionally, the arrival of Indo-European steppe ancestry brought another dollop of “hunter-gatherer” ancestry from beyond the fringes of Europe proper.

So what story can we tell of the transition between the Late Neolithic (LN) and the Early Bronze Age (ENA) in Europe? First, the proto-Indo-Europeans were people from the fringes and boundaries. Their genetics indicate some sort of influence from the Near East, likely via the Maykop people. But their roots were also deep in eastern Europe, from the local hunter-gatherers who had affinities with Siberians to their east and European hunter-gatherers to their west. From from this synthesis emerged something special, a warlike group of mobile pastoralists who quickly swept the field.

This reminds me of something from Peter Turchin’s book, War and Peace and War: The Rise and Fall of Empires. Populations on the borders or frontiers of ethno-cultural (and possibly political) zones may exhibit more group cohesion than those from “core” areas. The Indo-Europeans were a border folk. They may also take to cultural innovations more quickly, in The Making of a Christian Aristocracy it is clear that switching to the new religion occurred faster among elites in outlying regions than in the core.

A second issue, which is not proven, but may be possible, is that once the Indo-Europeans moved into the North European plain, they allied with residual hunter-gatherer populations. A classic enemy-is-my-enemy proposition. This would likely result in a higher proportions of Pleistocene ancestry in later generations due to assimilation.

The moral of the story is that often there is no final victory in the war. Human history is full of reversals.

The reality of cultural hitchhiking

Filed under: Anthroplogy,Cultural hitchhiking,Genetics,History — Razib Khan @ 2:55 pm

The figure to the left is from a paper, The mountains of giants: an anthropometric survey of male youths in Bosnia and Herzegovina, which attempts to explain why the people from the uplands of the western Balkans are so tall. Anyone who has watched high level basketball, or perused old physical anthropology textbooks, knows that average heights in the Dinaric Alps are quite high in comparison to the rest of Europe, matched only in the region around Scandinavia. The Dutch of late have been the world champions in height, and explanations such as recent selection and their high consumption of dairy products have been given. In this paper the authors point out that the people who live in the Dinaric uplands are not a population which consumes a inordinately high protein diet, at least in relation to their neighbors.

Rather, they suggest that the height of the people who reside in the Dinarics is due to a genetic factor. There is now good genomic evidence that selection accounts for at least some of the difference in height between Northern and Southern Europeans. That is, seems that there have been divergent pressures in these two locales, their genetic differences due to historical demography aside.

The exception to this north-south gradient is obviously in the Dinarics. Another way in which the Dinarics are exception is that it has the highest frequency of Y chromosomal haplgroup I. The other mode of haplogroup I is in Scandinavia. I1 is common among people who live in Sweden, while I2 among the peoples of the western Balkans. I has an interesting history because the vast majority of Mesolithic hunter-gatherer males in Europe belong to this haplogroup. It is very rare outside of Europe. This is in contrast to the other major European haplogroups, which are found outside of Europe at appreciable frequencies.

It is likely that I is indicative of a lineage which roots in Europe which go back to the late Pleistocene period after Last Glacial Maximum ~20,000 years ago. As the world warmed ~10,000 years ago small populations of hunter-gatherers rapidly expanded from their refuges and either most of the males were I, or in the drift process on the edge of the wave of advance I became very common. It is plausible that in terms of alleles which account for variation in height these hunter-gatherers were enriched for those conferring larger size. Cold weather populations tend to be larger. Additionally, they probably consumed a relatively diversified but high protein diet, allowing for greater median size than among farmers at the Malthusian carrying capacity.

But, there has been a lot of selection over the past 10,000 years, and I am skeptical that this correlation between I and height in Europe is anything but a coincidence. Rather, the phylogeny which I exhibits brings me to another issue which I think is not often highlighted: I1 in particular may have “hitchhiked” with the exogenous lineages such as R1b and R1a in early Indo-European society.

That is, in the patrilineal descent groups expanding across the landscape and monopolizing access to resources and mates, the non-invasive I somehow integrated themselves into the broader cultural complex, and partook in the plenty. Like R1b and R1a it exhibits a rake-like topology which suggests rapid recent expansion.

This would not be exceptional. The modern Russian state’s origins are in the polities created by Keivan Rus, who were famously Scandinavian. Rurik was by origin a Sweden, and his dynasty eventually came to encompass most of the eastern Slavic peoples, and rule over the Russian people and state until the 17th century. Because there were so any descendants of this dynasty it was possible to adduce its Y chromosomal haplogroup, N1c1. The kicker is that this is clearly a Finnic lineage, with the most recent evidence being that it is a remnant of a recent migration out of Siberia to the west. The implication here is that the direct male lineage of Rurik were assimilated into the Scandinavian culture and power structure, and were possibly chieftains of Finnic tribes somewhere along the Baltic littoral.

Another example is the House of Wessex. Alfred the Great is arguably the first true king of England. Here are the names of some of the earlier monarchs of the House of Wessex, Ceawlin, Cynric, and Cynegils. Even someone without a background in historical linguistics may be curious about whether these are Anglo-Saxons, and there is a line of thinking that perhaps the forebears of Alfred were British warlords, who “went Saxon,” in a fashion analogous to Gallo-Roman aristocrats who assimilated to Frankish-Germanic norms and forms in the 6th and 7th centuries in the Merovingian domains.

Overall what you see in the genetic data are many things, but rarely a straightforward story. Just as genes can impact culture (e.g., lactase persistence), so culture impacts the distribution of genes. Just as human polities are coalitions, so genetic lineages themselves in their distribution and evolutionary history exhibit fingerprints of these past socio-political events and ideas.

The coming reign of the Baby Boomer gerontocracy

Filed under: Gerontocracy,Psychology,Psychometrics — Razib Khan @ 1:22 pm

From Dawn to Decadence: 1500 to the Present: 500 Years of Western Cultural Life is one of my favorite books. It’s one of those works whose breadth and depth is such that I would recommend it to anyone. Jacques Barzun began writing this work when he was 84, and it was published in his 93rd year. Born in 1907 Barzun saw the full efflorescence of 20th century Western culture across much of its span firsthand. When people say that when you age you gain wisdom, surely in the domain of scholarship Barzun’s production in the last few decades of his life would qualify.

But not everyone is Jacques Barzun. If you read Intelligence: All That Matters or peruse some of Eliott Tucker-Drob’s work you will know that cognitive function declines with age beyond your twenties. Different subcomponents may decline at different rates. And, they decline differently in different people (e.g., some people may develop dementia, so their faculties will decline far faster at an earlier age). But, by and large any gains in experience or wisdom are going to be balanced against declines in raw analytic ability, as well as the slow entropic loss of information.

This is not an inconsequential matter. Our governing class is quite old. The average age in Congress may be 55 to 60, but it is almost certainly true that more senior members with more power and authority are older. The president of the United States is 70 years old. If you look at the plots in these figures by 70 there has been a notable drop in intelligence by this age, though again, it may vary from person to person.

But most important in light of these figures is that the Supreme Court is a lifetime appointment, and many of its members are quite old, an anticipate serving until they are quite old if they are younger. In the mid-1970s justice William O. Douglas had a stroke and was basically not mentally competent to serve. Because of this fact, and Douglas’ reluctance to retire his fellow justices basically did not take his vote into account. Three of the justices today are over the age of 70, with Clarence Thomas nearing that age, and two are over the age of 80.

When it comes to Congress, or even the President, there seems to be some sort of institutional support as well as the larger collective vote in the case of Congress, which might buffer the cognitive impact of a gerontocracy. But aside from law clerks Supreme Court justices have to rely on their own individual mental capacities.

The Mormon Church has a gerontocracy among its we openleadership. Even my most devout friends in the church sometimes found it amusing how old their leadership was, and how quickly they died in succession due to the seniority principle. But The Supreme Court is not the leadership of a relatively small church. It impacts our whole nation. This sort of gerontocracy is no laughing matter.

Will we openly speak of the age issue? I doubt it. Today the Baby Boomers are between the ages of 53 an 71. They are coming into their own as a cohort into the highest reaches of the gerontocracy. If there is any generation with the grace and humility to step aside for the greater good, it will not be this generation.

April 12, 2017

$150,000 only gets you so far….

Filed under: Cost of living,Culture — Razib Khan @ 10:31 pm

The above salary range seems accurate. I know newly minted PhDs in computer science may “only” get in the low $100,000 range at Google. So a salary in the mid six-figure range is totally reasonable with a few years of experience.
Recently a friend who is an engineer at Google in Mountain View got a transfer to Boulder, where they bought a house. He’d been trying to buy in Mountain View for a while…but that just wasn’t happening. Boulder isn’t cheap, with 178% the national average in cost of living. But it’s nothing compared to Mountain View, where the average housing cost is 7.5 times the national average.

What’s striking to me is the high variation in cost of living in American urban areas:

Overall cost of living
San Francisco 272
New York City 180
Seattle 177
Boston 170
Los Angeles 166
San Diego 166
Portland 140
Denver 128
Miami 123
Austin 117
Chicago 111
Minneapolis 109
Houston 102
Atlanta 102
Raleigh 102
Philadelphia 100
Phoenix 99
New Orleans 96
Dallas 95
Baltimore 90
Pittsburgh 88
Cincinnati 86
St. Louis 85
Des Moines 83
Memphis 74
Detroit 73

This website is wicked popular in Boston

Filed under: Blog,Blog stats — Razib Khan @ 1:22 pm
Traffic Feb 1 2017 to Apr 1 2017, top 10 cities
New York Boston
London New York
Sydney London
Los Angeles Los Angeles
Melbourne Chicago
Madrid Washington
Toronto San Francisco
Chicago Seattle
Washington Toronto
Brisbane Dallas

Weird pattern in terms of top cities that read this new version of GNXP. I’m comparing to the old blog over the same time…most of that is search engine traffic, so it’s not totally representative. The Australian overrepresentation is strange to me but it may be some Australian focused blog posts were promoted on some site down under. As search engine traffic increases on this website I’m assuming New York will be taking the top slot….

Fisherianism in the genomic era

Filed under: Evolutionary Genetics,Genetics — Razib Khan @ 1:07 am

There are many things about R. A. Fisher that one could say. Professionally he was one of the founders of evolutionary genetics and statistics, and arguably the second greatest evolutionary biologist after Charles Darwin. With his work in the first few decades of the 20th century he reconciled the quantitative evolutionary framework of the school of biometry with mechanistic genetics, and formalized evolutionary theory in The Genetical Theory of Natural Selection.

He was also an asshole. This is clear in the major biography of him, R.A. Fisher: The Life of a Scientist. It was written by his daughter.  But The Lady Tasting Tea: How Statistics Revolutionized Science in the Twentieth Century also seems to indicate he was a dick. And W. D. Hamilton’s Narrow Roads of Gene Land portrays Fisher has rather cold and distant, despite the fact that Hamilton idolized him.

Notwithstanding his unpleasant personality, R. A. Fisher seems to have been a veritable mentat in his early years. Much of his thinking crystallized in the first few decades of the 20th century, when genetics was a new science and mathematical methods were being brought to bear on a host of topics. It would be decades until DNA was understood to be the substrate of heredity. Instead of deriving from molecular first principles which were simply not known in that day, Fisher and his colleagues constructed a theoretical formal edifice which drew upon patterns of inheritance that were evident in lineages of organisms that they could observe around them (Fisher had a mouse colony which he utilized now and then to vent his anger by crushing mice with his bare hands). Upon that observational scaffold they placed a sturdy superstructure of mathematical formality. That edifice has been surprisingly robust down to the present day.

One of Fisher’s frameworks which still gives insight is the geometric model of the distribution of fitness of mutations. If an organism is near its optimum of fitness, than large jumps in any direction will reduce its fitness. In contrast, small jumps have some probability of getting closer to the optimum of fitness. In plainer language, mutations of large effect are bad, and mutations of small effect are not as bad.

A new paper in PNAS loops back to this framework, Determining the factors driving selective effects of new nonsynonymous mutations:

Our study addresses two fundamental questions regarding the effect of random mutations on fitness: First, do fitness effects differ between species when controlling for demographic effects? Second, what are the responsible biological factors? We show that amino acid-changing mutations in humans are, on average, more deleterious than mutations in Drosophila. We demonstrate that the only theoretical model that is fully consistent with our results is Fisher’s geometrical model. This result indicates that species complexity, as well as distance of the population to the fitness optimum, modulated by long-term population size, are the key drivers of the fitness effects of new amino acid mutations. Other factors, like protein stability and mutational robustness, do not play a dominant role.

In the title of the paper itself is something that would have been alien to Fisher’s understanding when he formulated his geometric model: the term “nonsynonymous” to refer to mutations which change the amino acid corresponding to the triplet codon. The paper is understandably larded with terminology from the post-DNA and post-genomic era, and yet comes to the conclusion that a nearly blind statistical geneticist from about a century ago correctly adduced the nature of mutation’s affects on fitness in organisms.

The authors focused on two primary species which different histories, but well characterized in the evolutionary genomic literature: humans and Drosophila. The models they tested are as follows:


Basically they checked the empirical distribution of the site frequency spectra (SFS) of the nonsynonymous variants against expected outcomes based on particular details of demographics, which were inferred from synonymous variation. Drosophila have effective population sizes orders of magnitude larger than humans, so if that is not taken into account, then the results will be off. There are also a bunch of simulations in the paper to check for robustness of their results, and they also caveat the conclusion with admissions that other models besides the Fisherian one may play some role in their focal species, and more in other taxa. A lot of this strikes me as accruing through the review process, and I don’t have the time to replicate all the details to confirm their results, though I hope some of the reviewers did so (again, I suspect that the reviewers were demanding some of these checks, so they definitely should have in my opinion).

In the Fisherian model more complex organisms are more fine-tuned due topleiotropy and other such dynamics. So new mutations are more likely to deviate away from the optimum. This is the major finding that they confirmed. What does “complex” mean? The Drosophila genome is less than 10% of the human genome’s size, but the migratory locust has twice as large a genome as humans, while wheat has a sequence more than five times as large. But organism to organism, it does seem that Drosophila has less complexity than humans. And they checked with other organisms besides their two focal ones…though the genomes there are not as complete presumably.

As I indicated above, the authors believe they’ve checked for factors such as background selection, which may confound selection coefficients on specific mutations. The paper is interesting as much for the fact that it illustrates how powerful analytic techniques developed in a pre-DNA era were. Some of the models above are mechanistic, and require a certain understanding of the nature of molecular processes. And yet they don’t seem as predictive as a more abstract framework!

Citation: Christian D. Huber, Bernard Y. Kim, Clare D. Marsden, and Kirk E. Lohmueller, Determining the factors driving selective effects of new nonsynonymous mutations PNAS 2017 ; published ahead of print April 11, 2017, doi:10.1073/pnas.1619508114

April 11, 2017

Coffee is not measured by its price

Filed under: Coffee,Culture — Razib Khan @ 10:48 pm

An interesting piece on a $1 coffee joint, Has Coffee Gotten Too Fancy?:

Mr. Konecny’s ambitions for Yes Plz go beyond selling a high-quality cup of coffee at that magic price point, though he knows that it sends a powerful message. What he wants to do is shift the very nature of coffee culture. He has no patience for what he calls the “culinary burlesque” of pour-over bars, with their solemn baristas and potted succulents. “It’s dress-up,” he said.
Those settings and presentations, he said, send the wrong message: that good coffee must also be expensive and fetishized.

I drink a lot of coffee. At work I’m known to drink 40 or 60 ounces in a day. I also like specialty coffees, dating back to when I lived in Portland and patronized the Stumptown on Belmont.

As someone who drinks black coffee I like the idea of a no frills establishment. But I also feel the piece’s opposition between cheap good coffee and expensive faux-good coffee is a bit much. In How Pleasure Works Paul Bloom elaborates on something that we know intuitively: it is not always the sensory aspect of how something makes you feel, but also the intellectual aspect of what something is in a more contextual and broad sense. I would pay a lot for legitimate Falernian wine without even knowing what it tastes like. To drink like Cicero would be enough.

Yes, sometimes you want the $1 coffee. But sometimes you want the burlesque experience.

Living as Loki, friendship before Ragnarok

Filed under: Culture,History — Razib Khan @ 9:45 pm

In Norse mythology Loki is a trickster frost giant who also plays a god. His relationship to the Aesir is complicated, but at the end of days when the world is nearing its final hours he is fated to stand against his erstwhile companions. I do not know much about the Marvel comics adaptation of Loki, though I have seen the films, and this element of alternating between good and evil is evident onscreen.

Does the fact that Loki is destined to stand against Odin negate all their experiences together? Is the full measure of a life the final act? I don’t think so.

Today we live in an age when he center is not holding. Politics and public life are polarizing. Apocalyptic language is in the air. Barack Obama was a socialist, a Communist, a Muslim. Now Donald J. Trump is the worst, thing, ever. And so on. There are two teams, and if you do not choose a team, you have lost the game before it is played. My pessimism about the possibility for a reinvigoration of a broadly liberal democratic order are for another post.

Recently my friend Heather Mac Donald wrote about her experience with protesters at Claremont McKenna. Her description of the student body’s hysterics are almost anodyne in how predictable they behaved. Rather, I was struck by how much invective Heather directed toward the silent faculty:

…Those professors also maintain that to challenge that claim of ubiquitous bigotry is to engage in “hate speech,” and that such speech is tantamount to a physical assault on minorities and females. As such, it can rightly be suppressed and punished. To those faculty, I am indeed a fascist, and a white supremacist, with the attendant loss of communication rights.

Of course not all faculty have abandoned classical liberal ideals. Nicholas Christakis and Alice Dreger are by any definition progressive liberals, but also adhere stridently to ideals of freedom of thought and speech. But both have been subject to abuse and personal attacks. They clearly fight on not because they are assured of victory, but because they believe in the justness of their cause.

Many of my liberal friends express some exasperation that I identify as conservative. But the fact of the matter is that the far Left writes off much of this country, and many of my friends, and arguably me, as a white supremacist and a fascist. Ours are not thoughts worth having in the eyes of the heirs of repressive tolerance. My liberal friends, being broad minded an of a tolerant bent, do not have sympathy with repression of thought. But at the end of the days when sides are taken what side will they choose?

I think here of an academic who is jaded and contemptuous of the infantile antics of the campus Left. He is worried that their provocations will result in the academy being targeted by the political Right. He does not relish conflict. Like me, he wants to be left alone to explore the topics which interest him. We share a mutual interest in evolutionary genetics. But, when and if the fight comes he does admit he must march with his colleagues, no matter how loony, and defend his side.

We both wish the world were not this polarized. But what we wish is not always what is. But until Ragnarok we can continue to drink beer and fight our battles shoulder to shoulder as friends. Neither of us want the Ragnarok of this liberal democratic republic to come, and I still hope it doesn’t. But we both understand that on that day we’ll be on different sides. And I’m OK with that. Life is not perfect, we do the best we can.

Addendum: Cool trailer:

April 10, 2017

Colonizing the past

Filed under: History — Razib Khan @ 11:54 pm

In 1793 the Macartney Mission went to China to open up the country for the British. The overall evaluation is that it failed. The Chinese under the Qing dynasty were in the last throes of the Indian summer of a great demographic expansion dating back three hundred years, capped off by an era of peace which had lasted more than 100 years. The Qianlong Emperor was in the 57th year of his reign. And he firmly rejected all British entreaties. China was the Middle Kingdom. It did not have European wares. It did not need European wares. It could easily dismiss European concerns and sensitivities.

Or so Qianlong and his court believed. Within 50 years the British would defeat the Chinese on their home turf, and impose a humiliating peace upon them. Over the next few decades European powers would begin to dissect the rotting carcass of late Qing China, which was also being eaten alive from the inside by convulsions such as the Taiping rebellion.

Though it was difficult for people at the time to perceive, and in particular the Chinese, the signs were already present in 1793 that the British star would ascend, while that of the Chinese would dim in comparison. The Chinese economic system was at its Malthusian carrying capacity, and had squeezed all it could out of the margins of Adam Smith’s classical factors of production, land, labor, and capital. In contrast, the British were in the midst of a revolution in economic production driven by innovation would would explode the underlying parameter of growth, all the while restructuring their social conditions so as to undergo demographic transition.

The British were inventing the modern economy. The Chinese were nursing along the classical agricultural stationary state as best as they could.

Aspects of this were already evident to the British implicitly. McCartney refused to kowtow to the Chinese Emperor, maintaining dignity, whereas previous factors would likely have abased themselves. The period around 1800 in India also saw the shift away from the traditional accommodationism of the East India Company with native cultural forms and practices, toward exporting elite British folkways in toto to overseas administrative posts.

In general people living in an age of transition don’t perceive the transition themselves, and continue to fixate on earlier assumptions and truths. The period between the Berlin Conference in 1884 and the outbreak of World War I saw the high tide of European colonialism and hegemony, but the seeds of its relative decline were already there. The United States of America became the largest economy early in the 20th century. British, French, and German intellectuals may have had their disputes and contributions in those first decades, but the future was already going to be across the Atlantic.

Today I feel that many Americans are living in the past, and not admitting and acknowledging that the present is pointing to the future. The world is becoming genuinely multipolar. There is more than one sun in the sky. Though there are nearly 1 billion people speaking English on the internet (often second language speakers), there are 750 million Chinese speakers. As the year 2020 approaches we’re living in a genuinely multipolar and multicultural world, but a lot of the discussion I see on my part of the internet is about white colonialist males. As if those are the only bright white suns in the sky. Men like McCartney. But the fixation of cultural elites is often a reflection of the last war, and past priorities, just as science fiction futures reflect the present. Change is in the air, even if we don’t realize it….

Sexual selection decreasing difference

Filed under: Evolution,Genetics,Sexual Selection — Razib Khan @ 10:32 pm

Sexual selection is often considered a driver of diversification of a lineage. I was introduced to the concept in Jared Diamond’s The Third Chimpanzee, where he suggested that racial differences in appearance might be due to sexual preference, following a suggestion originally made by Charles Darwin. Though sexual selection emerges now and then as a deus ex machina in discussion sections of papers, in general it hasn’t panned out addressing this topic.

But a new paper using shorebirds offers results which oppose this sort of inference, in that sexual selection may be a homogenizing force. Basically the authors used the fact that shorebird lineages have related monogamous and polygamous species. They looked at species richness and genetic diversity using STRUCTURE and microsatellites.

Polygamy slows down population divergence in shorebirds:

Examining microsatellite data from 79 populations in 10 plover species (Genus: Charadrius) we found that polygamous species display significantly less genetic structure and weaker isolation-by-distance effects than monogamous species. Consistent with this result, a comparative analysis including 136 shorebird species showed significantly fewer subspecies for polygamous than for monogamous species. By contrast, migratory behavior neither predicted genetic differentiation nor subspecies richness. Taken together, our results suggest that dispersal associated with polygamy may facilitate gene flow and limit population divergence. Therefore, intense sexual selection, as occurs in polygamous species, may act as a brake rather than an engine of speciation in shorebirds.

A reminder that lots of theorizing may lead you nowhere fast, but a quick empirical check can be very humbling. I’m not sure as to the generality of this result, and ultimately it probably has to do with reproductive variance. But it is a starting point.

Addendum: Overall Geoffrey Miller’s The Mating Mind is probably wrong in most of the details, though perhaps on the most general level there may be something there (I’m wondering particularly in regards to mutational load). But it’s a decent introduction to sexual selection theory in  human context, and has a lot of interesting ideas. And Miller is actually a good writer as far as scientists go.

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