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March 31, 2012

When little differences matter a great deal

Filed under: Altruism,Anthroplogy — Razib Khan @ 10:37 pm

In the comment below Clark alludes to the fact that Jonathan Haidt kept reiterating that even if there were differences between populations due to recent evolution, if it was due to selection on standing variation upon quantitative traits then the between group variation would be dwarfed by within group variation. He didn’t quite say it like that, but I’m sure that’s what he meant. For example, there is now evidence that alleles which can explain the small height difference between Northern and Southern Europeans have been subject to natural selection. Most of the variation obviously remains within the groups; you can’t guess that someone is Italian or Dutch just based on their height. There are many tall Italians, and many short Dutch. But on average there are differences between the groups which can be attributed to genes, and those genes seem to have been targets of selection.

This is good as fair as it goes…but small average differences may not necessarily be marginal. That is because sometimes you select from the tails of a distribution. For example, if you want to ascertain which population will produce more N.B.A. players, ...

June 14, 2011

Band of brothers at war

The fruits of human cooperation

ResearchBlogging.orgThe Pith: Human societies can solve the free rider problem, and generate social structure and complexity at a higher level than that of the band. That implies that much of human prehistory may have been characterized by supra-brand structures.

Why cooperation? Why social complexity? Why the ‘problem’ of altruism? These are issues which bubble up at the intersection of ethology and evolution. They also preoccupy thinkers in the social sciences who address fundamental questions. There are perhaps two major dimensions of the parameter space which are useful to consider here: the nature of the relationship between the cooperators, and the scale of the cooperation. An inclusive fitness framework tracks the relation between altruism and genetic relatedness. Reciprocal altruism and tit-for-tat don’t necessarily focus on the genetic relationship between the agents who exchange in mutually beneficial actions. But, in classical models they do tend to focus on dyadic relationships at a small scale.* That is, they’re methodologically individualistic at heart. So all complexity can be reduced to lower orders of organization. In economics a rational ...

May 4, 2011

We, Robot & Hamilton’s Rule


The original robots

We are haunted by Hamilton. William D. Hamilton specifically, an evolutionary biologist who died before his time in 2000. We are haunted because debates about his ideas are still roiling the intellectual world over a decade after his passing. Last summer there was an enormous controversy over a paper which purported to refute the relevance of standard kin selection theory. You can find out more about the debate in this Boston Globe article, Where does good come from? If you peruse the blogosphere you’ll get a more one-sided treatment. So fair warning (I probably agree more with the loud side which dominates the blogosphere for what it’s worth on the science).

What was Hamilton’s big idea? In short he proposed to tackle the problem of altruism in social organisms. The biographical back story here is very rich. You can hear that story from the “horse’s mouth” in the autobiographical sketches which Hamilton wrote up for his series of books of collected papers, Narrow Roads of Gene Land: Evolution of Social Behaviour and Narrow Roads of Gene Land: Evolution of Sex. ...

October 11, 2010

Can’t we all just get long: evolution of altruism edition

Filed under: Altruism,Evolution,Genetics,Social Theory — Razib Khan @ 12:48 am

Samir Okasha is a philosopher of science and author of Evolution and the Levels of Selection. So his recent comment in Nature, Altruism researchers must cooperate, is informed by a scholarly background in these controversies. From what I can gather Okasha’s stance in this case is to “push back” on Nowak & Wilson in particular, who are the ones making positively audacious claims:

All this disagreement creates the impression of a field in massive disarray. In reality, many of the players involved are arguing at cross purposes. Nowak and his colleagues, for instance, have developed a mathematical model that they claim provides a more direct way to calculate the evolutionary dynamics of a social trait such as altruism…However, they overlook the fact that inclusive fitness theory explains what organisms are trying to maximize. It is not just a tool for calculating when a social trait will evolve.

Likewise, in arguing that ecological factors, rather than kinship, are key to the evolution of social-insect colonies, Wilson is imposing a false dichotomy…To fully understand how these colonies evolve, researchers need to consider ecological factors and relatedness. Whether they stress the importance of one over the other will depend on the question they are asking. For example, relatedness has proved crucial to understanding conflicts between the queen and her workers over the production of male versus female offspring in ants, bees and wasps. For questions about how tasks are allocated to the workers in an ant colony or why the size of colonies differs across species, ecological factors are probably more relevant.

As a “big picture” guy Okasha takes a step back, and compares evolutionary biology to physics (not favorably I might add):

Much of the current antagonism could easily be resolved — for example, by researchers situating their work clearly in relation to existing literature; using existing terminology, conceptual frameworks and taxonomic schemes unless there is good reason to invent new ones; and avoiding unjustified claims of novelty or of the superiority of one perspective over another.

It is strange that such basic good practice is being flouted. The existence of equivalent formulations of a theory, or of alternative modelling approaches, does not usually lead to rival camps in science. The Lagrangian and Hamiltonian formulations of classical mechanics, for example, or the wave and matrix formulations of quantum mechanics, tend to be useful for tackling different problems, and physicists switch freely between them.

History shows that, despite its enormous empirical success, evolutionary biology is peculiarly susceptible to controversy and infighting. This is particularly true of social evolution theory, in part because of its potential applications to human behaviour. In the 1970s and 1980s, for instance, left-wing scholars bitterly rejected biological explanations for phenomena such as religion and homosexuality, because they feared such explanations would be used to justify a continuation of existing inequalities.

When evolutionary biologists start to look like macroeconomists from the outside, it’s not a pretty picture.

July 13, 2010

The Price of Altruism


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Sometimes in a narrative you have secondary characters who you want to revisit. What do to do after the story is complete? An convenient “work-around” to this problem is to find the story rewritten from the perspective of the secondary character. In broad strokes the picture is unchanged, but in the finer grained shadings different details come into sharper relief. Though the exterior action may be unaltered, it gains different context, and the interior motive may radically alter, as the nature of subjective perspective matters so greatly in the last instance. In many ways Oren Harman’s The Price of Altruism reads to me like a narrative rewritten from the perspective of a character who was a supporting protagonist in other stories. George Price, almost a novelty act elsewhere, now becomes the primary point of view character.

I could almost say that Harman, a historian of science, has given us a novel from a “shared universe” of stories. That universe is the real world. The other stories are the lives of great scientists, and the plot consists of the working out of their ideas. In the acknowledgments Harman alludes to the wide range of works where fragments of George Price’s life filters through. I have read many of the mentioned works, The Darwin Wars, Defenders of the Truth, and Narrow Roads of Gene Land. In all of these George Price cuts a quixotic figure, mercurial, brilliant and exceedingly eccentric. His plain biography already peculiar. Price began his career as a chemist, shifted to journalism and became what we today would term a professional “skeptic,” then entered into a period of productivity as an evolutionary theorist of some major impact, and finally spent his last years attempting to live the life of a serious Christian who followed God’s commands to the best of his abilities. He died tragically, committing suicide in his early 50s in 1975, homeless, destitute, and serious ill.

Much of what I already know comes through the memories of William Hamilton in his collections of papers, titled Narrow Roads of Gene Land. In Narrow Roads of Gene Land Hamilton admits that he did not perceive in totality the implications of Price’s eponymous equation when he first encountered it (in particular, he did not initially comprehend that the two elements within the Price equation allowed for the possibility of group selection as you move up the nested hierarchies of organization and reassign the elements to ascending levels). In The Price of Altruism Oren Harman reiterates this reality, but, importantly he emphasizes that Price felt that it was Hamilton alone in all the world who had perceived the equation’s nature upon first encountering it. The back story, which is told in Narrow Roads of Gene Land, is that George Price had difficulty in getting his papers in this area published because the referees simply did not see the implications. Hamilton, perceiving the importance of Price’s ideas, connived to gain publication by making his own work conditional on the acceptance of Price’s paper (which he cited). As Hamilton already had a reputation the game worked.

The necessity of these strategies makes more sense in light of Price’s unconventional background and affect.  In evolutionary biology Price was self-taught, and he entered the field in large part because he was interested in the topic, and perceived that he was going to make some difference in the world. He arrived in London in the late 1960s, impressed people at the Galton Laboratory and managed to obtain a research grant and desk, and became an important stimulator of and collaborator with both William Hamilton and John Maynard Smith, arguably Britain’s two most prominent theoretical evolutionary biologists at the time. Price’s relationship to John Maynard Smith is referenced in Hamilton’s own biography, as well as third person narratives such as The Darwin Wars and Defenders of the Truth, but The Price of Altruism fleshes out many of the details. While Price extended Hamilton’s original work on inclusive fitness, for Maynard Smith he served more as a prod and collaborator as they explored the intersection of game theory and biology which eventually led to the ideas outlined in Evolution and Theory of Games. The “hawk” and “dove” morphs made famous by Richard Dawkins in The Selfish Gene go back to Maynard Smith’s work, but the terms themselves were of Price’s invention according to Harman. If I read Harman’s chronology correctly Price was already a fervent Christian by this time, having left atheism in the same period as he launched his career as an evolutionary biologist, and there is some hint that the term “dove” may have been influenced by his particular religious leanings. This possibility seems all the more amusing in light of Dawkins’ later career as an atheist polemicist. Price’s last contribution to evolutionary biology was an explication of Fisher’s fundamental theorem of natural selection. This formalism has been the subject of so much deep analysis, such that I think Price’s interest in it prefigured his later stab at Biblical textual analysis!

The Price of Altruism is a biography of a scientist, so naturally there’s a great deal of science. The meat and heart of the work is George Price’s life trajectory, with all its travails (many) and triumphs (few, but lasting and of importance). Yet the story begins with an exploration of the lives and opinions of men who seem of a different age, Thomas Huxley and Peter Kropotkin. Huxley and Kropotkin were archetypes, who anticipated two streams of evolutionary ecology and social theory which battled it out through the 20th century. Huxley was a man who saw nature as “red in tooth and claw,” the working out of amoral competitive forces, and human virtue as having emerged out and above nature, just as he had risen up from his working class origins to eminence. Kropotkin reflected a Russian viewpoint which saw cooperation as the norm, and competition as the deviation. For him virtue emerged from our natural tendencies. Lee Alan Dugatkin covers much of the same ground in The Altruism Equation. Great men who you meet elsewhere inevitably make cameo appearances in Harman’s narrative; R. A. Fisher, the brilliant cipher, J. B. S. Haldane, the hereditarian Marxist, and Sewall Wright, the American (also see The Origins of Theoretical Population Genetics). The bright lights of Price’s generation also make prominent appearances; William Hamilton and John Maynard Smith, their characters manifesting no great surprises, but also the schizophrenic genius Robert Trivers, with whom Price perhaps shares a great deal excepting his dark ending, as well as E. O. Wilson.

All of these individuals have an interest in evolutionary biology, but biology of a behavioral sort. Though molecular evolutionists such as Richard Lewontin and Motoo Kimura are references in The Price of Altruism, they’re ancillary to the thrust of the book’s central idea (though Lewontin seems to serve as a type, the brilliant scientist who saw the import of Price’s equation too late to engage in a productive exchange with George Price himself). Evolution, like theoretical physics, spans may domains of subject, from the aggregations of millions of individual life forms, to evolution of elements within individual genomes! The Price equation’s generality is such that it does speak to the phenomena which bubble just above the level of organizations of the substrate, DNA itself. But George Price’s focus was on higher, not lower, levels of organizations, human societies. Oren Harman makes this clear, for he brings to light Price’s correspondence with Paul Samuelson, one of the greatest economists of the 20th century. Before Price left for London and began his collaboration with Hamilton and Maynard Smith on altruism, he fancied reconstructing the basis of 20th century economics. By the end of his life Price suggested that he was going to go back to this initial impulse, and attempted to renew his correspondence with Samuelson in the hopes of obtaining a research fellowship of some sort. Price also engaged with the behavioral psychologist B. F. Skinner, though as with many of his encounters it seems that the two soured on each other, in part due to Price’s impolitic tendencies.

George Price’s aim was to explain human cooperation, altruism. In short, goodness. This is the domain of angels, but his analytical bent mean that he could not let the phenomenon lay. He had to break it down, reconstruct its fundamentals, and elaborate on how and why goodness, altruism, manifested itself in the world. From the details reported in The Price of Altruism I would have to admit that Price himself was a Janus-like figure, often being in a manifestly selfish fashion, abandoning his family to follow his intellectual bliss, and yet also radically altruistic, allowing himself to be exploited by the dregs of the London underclass near the end of his life because scripture told him so (or his reading of scripture). What I had previous read did not emphasize Price’s selfishness, his need to satisfy his own wants, and place his own elective priorities ahead of the mandatory ones which decency bound him to honor (e.g., supporting his wife and daughters). Harman has a rich catalog of George Price’s selfish actions and the small vendettas which wracked his soul. No saint was he. Much of what Harmon recounts was simply not evident from other sources. Perhaps in Hamilton’s case he wished to highlight the positive aspects of a good friend who had died tragically. More plausibly I suspect that Hamilton was simply not aware of the selfish sequence of acts which led George Price to the Galton Laboratory in the late 1960s. And it was during this period that George Price became a zealous Christian and a radical altruist. Hamilton’s perceptions may simply have been colored by the slice of Price’s life to which he was privy.

Oren Harman wonders at the end of the book if George Price may have been rather far along the asperger’s spectrum. If so, combined with his fierce intelligence, one is not surprised that Price exhibited a fixation on why and how humans behaved, and why and how it came to be that humans did not seem to be rational psychopaths. Though I do not know if, and honestly do not believe, that George Price was a rational psychopath, in The Price of Altruism Oren Harman paints a picture of a man with immediate urges and impulses, earthy hedonic priorities, and a strong tendency to discount the costs which his choices may have for those close to him. George Price was not the first man to not be a good father, but he was one who perhaps wondered why there were good fathers and bad fathers, those who followed their bliss despite the consequences to their progeny, and those who sacrificed so that their children could enjoy the comforts and pleasures which they elected to forgo. The science is well elucidated in works such as Unto Others, The Origins of Virtue and The Evolution of Cooperation. The Price of Altruism is rather a case study not of the theory of altruism, but of the concrete embodied human experience which eventually gave fruit to an important slice of the theory of altruism. From the small details of his day-t0-day actions, to the arc of his life, George Price played out some of the implications of his own intellectual edifice, both through contradiction and confirmation.

Recommended Reading: The Darwin Wars, The Evolutionists, A Reason for Everything, Narrow Roads of Gene Land, Natural Selection and Social Theory, The Origins of Theoretical Population Genetics, Sewall Wright and Evolutionary Biology, R.A. Fisher: The Life of a Scientist, Defenders of the Truth, Unto Others and The Selfish Gene.

July 1, 2010

Hamilton’s Rule vs. Increasing returns to cooperation

If you have even a marginal interest in evolutionary biology you will probably have heard of Hamilton’s Rule, a simple formal representation of the logic whereby a gene which favors altruism may spread through a population: rB > C, where r = coefficient of relatedness on the gene in question, B = benefit to those related, and C = cost to oneself. The idea is almost trivially obvious. Consider that you are in a situation where you are faced with the possibility of aiding your full sibling at a cost to yourself. Now imagine that you carry a single allele which favors altruism toward close relations. Your sibling has a 50% probability of carrying that allele identical by descent (let’s stay haploid for simplicity). From a “gene’s eye view” it benefits the allele to predispose you to helping your kin in direct proportion to the probability that your kin carry that allele. In other words the logic underlying inclusive fitness isn’t really that abstract, it is ordered around the benefits and costs to the theoretical genes which manipulate social behavior over the long term. This explains why the evolutionary biologist J. B. S. Haldane responded “…I would to save two brothers or eight cousins,” when asked if he would save his brother from drowning. The genetically relatedness to a sibling is 1/2, to a cousin 1/8. 2 X 1/2 = 1 and 8 X 1/8 = 1, basically equivalent to yourself. Evolutionary altruism is obviously somewhat different from common sense altruism, because you’re averaging out the behavior of many individuals over a time window.

The fascinating back story behind the development of this sort of formal thinking is recounted in W. D. Hamilton’s first collection of papers, Narrow Roads of Gene Land: Evolution of Social Behaviour. An elaboration upon the core logic of Hamilton’s Rule in two seminal papers revolutionized our understanding of the evolution of sociality in the 1960s; Hamilton was proud of how widely cited his original papers were. John Maynard Smith’s evolutionary game theory and Robert Trivers reciprocal altruism emerged out of the same ferment (Trivers’ acknowledges the debt to Hamilton in Natural Selection and Social Theory). More recently E. O. Wilson and David Sloan Wilson have been arguing for a rehabilitation of more complex models of the origins of sociality through multilevel selection theory.


But what about Hamilton’s original ideas, the core elements of inclusive fitness? Their spareness rendered them analytically tractable, but like all models the original formalism made some simplifying assumptions. Relatively weak selection pressures, as well as additivity of fitness effects, were two major axioms, and ones which Hamilton defended in Narrow Roads of Gene Land. A new paper in Science argues that the assumptions rendered the model too simple to be of more than qualitative or heuristic utility in most cases. They modify the Hamiltonian framework by including nonlinear fitness distributions as well as stronger selection coefficients in the context of microbes. A Generalization of Hamilton’s Rule for the Evolution of Microbial Cooperation:

Hamilton’s rule states that cooperation will evolve if the fitness cost to actors is less than the benefit to recipients multiplied by their genetic relatedness. This rule makes many simplifying assumptions, however, and does not accurately describe social evolution in organisms such as microbes where selection is both strong and nonadditive. We derived a generalization of Hamilton’s rule and measured its parameters in Myxococcus xanthus bacteria. Nonadditivity made cooperative sporulation remarkably resistant to exploitation by cheater strains. Selection was driven by higher-order moments of population structure, not relatedness. These results provide an empirically testable cooperation principle applicable to both microbes and multicellular organisms and show how nonlinear interactions among cells insulate bacteria against cheaters.

The bottom line here is that the authors are indicating that a simple framework with the parameters of Hamilton’s original formalism can not explain the various forms of altruism found among microbes, even ubiquitous ones such as biofilms. One should not be surprised, as the problem of altruism was not solved by inclusive fitness in its details, though many use it in a hand-waving manner, i.e., “…everyone knows….” To correct this impasse the authors modify Hamilton’s Rule:

fd1_1

Some of the parameters are now bold. That means they’re vectors, not scalars. Basically lists of variables. First in the list for r is the original coefficient of relatedness, with subsequent elements representing higher orders of relatedness. b represents the benefits to noncooperating morphs as a function of social environment, the frequencies of cooperators and noncooperators. The cost to the focal individual remains the same. Finally, m are the moments for the cooperators (measuring distributions of fitness in terms of their shape) and d represents the difference between cooperators and noncooperators of the distribution. When fitness effects are totally additive, that is there are no nonlinearities and conditionalities of genotype fitness on environment, the second part of the equation falls away, and r and b reduced to their first elements, so you have a classical form of Hamilton’s Rule.

Figure 1 illustrates the aspects differentiating a classical vs. modified Hamiltonian model:

ham1

Basically the simplifying assumptions in Hamilton’s original model is illustrated by panel A. The authors claim that the assumptions allow for no quantitative prediction of real structured altruism which we see. Figure 2 has some experimental data:

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Here’s the text:

Parameters of the generalized Hamilton’s rule measured in an experimental population of sporulating Myxococcus bacteria. (A) Absolute fitness of a cooperator strain (blue circles) and a cheater strain (red diamonds) as a function of their frequency within groups. Data points are independent experimental replicates; lines, regression model fit to data. (B) Fitness terms in Eq. (1), calculated from the data shown in (A). Green diamonds, benefit vector b; purple circles, genotype-dependence vector d. Points show best-fit model (±SD from bootstrapped data). (C) Initial distribution of cooperators among groups for a specific experimental population. (D) Social structure terms in Eq. (1) were calculated for the population shown in (C). Blue, cooperator moments m; red, noncooperator moments mnon; black, relatedness vector r.

As you can see in panel A there’s frequency dependence going on here. Cooperators run up against a wall, but the frequencies at which they’re fitter than the noncooperators is rather high. Panel B is important because it shows that the benefits really accrue at the higher moments, now the lower additive one. This means that higher level population structure and nonlinearities when viewed on an individual scale are very important. Figure 3 illustrates the nature of frequency dependence, and the conditions where cooperators flourish and cheaters can persist:

ham3

Since higher order structure is critical parameters such as migration between groups are important to keep track of us. More experiments obviously need to be done here, I’m not convinced that one model can explain-it-all. But, there are obvious limitations to the classical Hamiltonian framework in many situations. One of the major points in this paper which jumped out at me was the following: “…increasing-returns nonadditivity allows cooperation to evolve at levels of population structure comparable to that seen among social insect colonies.” Increasing returns is a concept which is important in economics in understanding how technological innovation has allowed for productivity gains over the past two centuries. Human social systems are complex, almost baroque to a fault, and their byzantine structure can easily be dismissed as random acts of contingency. But increasing returns to cooperation may explain the ubiquity of more complex orders than we would expect. And yet here we see it on the scale of bacteria! The logic of non-zero sum is deeply rooted in the nature of life, but the next stage is to flesh out how it produces such rich behavioral phenomena. Endless behaviors most ornate!

Smith J, Van Dyken JD, & Zee PC (2010). A generalization of Hamilton’s rule for the evolution of microbial cooperation. Science (New York, N.Y.), 328 (5986), 1700-3 PMID: 20576891

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