Discrete continuity in genetics

In the post below on skin color within a multiracial family I made the point that genetics is inherited in a discrete fashion. In the post-genomic era, or even the post-DNA era, this seems intuitively clear. Our genetic sequence, our genome, is a string of precisely four base pairs, A, G, T and C. The genome is digital, not analog. Case closed, right?
Not really. One of the main reasons I wrote the post below is the consistent misconception that genetics is blending, that children are a mix of the essences of their parents. This captures the expectation, but the variance. A natural inference of this model is that variation is diminished over the generations as it is homogenized through a process of mixture. Because Charles Darwin held to a system of blending inheritance he had to come up with ingenious ways to perpetuate and replenish variation. R.A. Fisher saw that Mendelianism was a way out, that discrete inheritance preserved information and genetic variation from generation to generation in full, mitigating the need for high mutational rates to battle homogenization, or to conceive of artificial barriers to breeding between demes.
Though it is easy to assert that Mendelianism “naturally” leads to the perpetuation of extant variation, it was harder to come to this consensus. One of the early posts on this weblog dealt with the early 20th century battle between the Mendelians and Biometricians. A large number of the former conceived of themselves as rebels overthrowing the outmoded Darwinian model, while the Biometricians fancied themselves the heirs of Charles Darwin. Under the leadership of Karl Pearson the Biometricians held that the Mendelian model could not account for continuous variation in phenotype, such as the famous bell curve which describes the nature of traits such as height or intelligence. This was nonsense, as some early Mendelians saw, and Will Provine in his book The Origins of Theoretical Population Genetics seems to suggest that one of the main blocks was simply a conflict of personality. Though Karl Pearson was no Fisher, he was a genius in his own right, and the basic reality that discrete processes can approximate continuous ones should have been clear to him.
Get it? If not, click below the fold for some graphs which I believe elucidate the issue pretty clearly.

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Moral sentiments and Material Interests

Not by Genes Alone, Peter Richerson and Robert Boyd, eds., Chicago, 2005.
Moral sentiments and Material Interests, Herbert Gintis, Samuel Bowles, Robert Boyd, and Ernst Fehr, eds., MIT, 2005.

Moral sentiments and Material Interests is, from my point of view, an enormous advance on all the orthodox economics I’ve ever read. My primary complaint is “What took so long?” For decades now economics has been spreading disinformation, and it’s about time that they started looking at reality. (The ev psych ideas found in the Gintis book are more fully developed in Not by Genes Alone. I should note that both books include a lot of technical argument which I haven’t even touched upon. What I’ve written here is only a summary of the conclusions, written from the point of view of a non-biologist and a non-economist).

The book’s starting point is an empirical look at the actual economic behavior of individuals, in order to see whether it matches the rational-self-interest assumed by economic theory. It is found that it doesn’t, and the actual behavior observed is next interpreted in terms of evolutionary psychology. Finally, the political and social significance of these new observations is sketched.

The empirical studies are standard cash-incentive psych lab tests designed to find out where people actually stand on the altruism / self-interest scale. In general, the tests find that people behave more altruistically than they would if they decided according to rational self-interest. (The tests also find that the degree of altruism varies according to culture, and is not a universal).

The results of these experiments square with my own convictions, but I’ve always felt that this kind of artificial, low-payoff game-playing is of only moderate scientific value — there’s even some evidence that the authors themselves think this way. To me the real story is that there’s never been any evidence at all that economics’ assumption of individual economic rationality is valid, and a lot of evidence that it isn’t. The rationalizations found in Friedman’s Positive Economics have allowed economists to rely thoughtlessly on these unproven assumptions for about five decades, and if a few little experiments are required to convince them to drop this inaccurate and unproven default, that’s cool with me. But it’s a little like someone cherry-picking Bible verses to make their point to the Vatican.

The authors define three mechanisms leading to altruism and social cohesion: strong reciprocity, conformity, and “costly signaling”. These are made possible by innate dispositions evolved in two steps — simple reciprocity first at the early primate small group level, and the more complex behaviors next at the early human. Altogether they make possible genetic selection for altruism, via net fertility advantages for all members of organized social groups (not simply biological groups or kinship groups) which are successful because their members behave altruistically. Biological competition within the group is suppressed by non-innate social and cultural mechanisms, giving an advantage to members of the group on the average, but not to every individual. This way, with gene-culture coevolution and mutualism, there can be genetic selection for a degree of innate altruism in a way that there could not be without culture and society, which form a kind of artificial environment.

“Strong reciprocity” is what replaces “rational self-interest”. It consists of the weak reciprocity described by Axelrod (initial cooperation, continued until the partner defects) plus an additional altruistic propensity to punish defectors even if there’s no personal advantage in doing so. In a society of strong reciprocators (altruists both in giving and in punishment), defectors do not have an advantage, whereas in a society of non-punishing altruists, the defectors have an advantage which causes the defector gene to drive out the altruist gene.

Two other behaviors are mentioned. “Conformity” is a weaker principle explaining social uniformity in the absence of the threat of punishment, and mostly applies to cases in which there is no clearly-perceptible advantage or disadvantage for the individual, so he just does what everyone else does. “Costly signaling” only appears in one chapter, which uses the biological concept to explain generosity of the potlatch / largesse / big man type. To me these are less immediately interesting than strong reciprocity, though “costly signaling” is a step on the way toward defining a more complex heirarchal society extending beyond the face-to-face level.

A significant advantage of this book is that it describes a social world which, like the world observed and described by historians, has “multiple equilibria and tipping points” and is thus less stable and less predictable than the imaginary world of equilibrium economics.

In the final chapter Bowles and Gintis point out that local community is always grounded on a fundamental ethic of strong reciprocity. They describe it as a positive force which is usually wrongly maligned by the partisans of the market, the state, and elite culture. This brings them close to the communitarians, for whom the local community is a valid and necessary third leg of society, distinguishable (and sometimes at odds with) both pure market behavior and the state. (A lot of liberationist and libertarian ideology is hostile to the naive sorts of strong retribution that make small-group community possible).

The three innate principles described by these authors can be thought of as a ground for ethics, and the authors speak openly of “trust” and “fairness”. However, all actual ethics involves further cultural processing, beyond the innate foundation. For one example, one of the great advances making civilization possible was the suppression of vendetta and feud, which are completely natural developments of “strong reciprocity”. For another, the mechanisms of natural ethics described here work best at the face-to-face level. The description, much less the attainment, of fairness (the goal of strong reciprocity) within a large, complex, multi-level society is an extremely tricky and difficult task indeed. (The authors do touch on these questions, and they cite Fried’s Evolution of Political Society, which sketches a general view of the move toward complex society).

Anyway, after about fifty years, economics seems to be returning to the real world.

(Slightly revised Sept 29)


My post got a bit of attention from Donald Luskin:

If the nature of selfishness is more complicated that economics typically assumes, if it is indeed tied up in considerations of family, friends, nation, species — whatever — then let the science of economics try to adopt itself to those complexities.

I have trouble thinking of this as a useful addition to the theory of rationality. It reminds me of the Chinese philosopher Chuang Tzu’s humorous mysticism: “Yes, I’m selfish! But I’m selfish for the whole universe, not just for me!”

I also have a new piece up at http://www.idiocentrism.com/lazear.htm

Far Left sociobiology

The frogs at point me to this article, Anarchism and Social Nature, in a Left-anarchist publication. The focus of the piece is a review of The Blank Slate by Steven Pinker, and here is the punchline:

We, along with most other ideologies on the Left, have based our theory on a mistaken concept of human nature. We have learned over the years to distrust words like sociobiology, evolutionary psychology, cognitive science, and above all that dreaded buzzword, ‘hard-wired’ – yet we can no longer ignore the fact that these sciences are probably right about human nature.

has , so I’ll hand it off to them.

Related: The Conflict Within – The Left’s Version of Creationism, The Turning of the Tide.

Digit ratio predicts sport performance in female twins

From the BBC:

A King’s College London team found women whose ring finger is longer than their index finger are more likely to achieve higher levels in sport. The ratio between the fingers has already been linked to traits in men like cognitive ability and sperm count. The study appears online in the British Journal of Sports Medicine. The researchers, from King’s Twin Research Unit, examined hand X-ray images of 607 female twins aged 25-79 from the UK. In each case they measured the lengths of the second and fourth fingers of each hand. The volunteers also ranked their highest level of achievement in a list of 12 sports on a questionnaire. The researchers found women with longer fourth fingers were significantly more likely to be among the top achievers in all the sports listed.

I can’t find the paper online, but I’d like to see it because the news report hints at that the result has a more fascinating twist.

Lead researcher Professor Tim Spector said: “The reasons for these findings are unclear. “Previous studies have suggested the change in finger length was due to changes in testosterone levels in the womb but we also found that finger length was 70% heritable with little influence of the womb environment. “This suggests that genes are the main factor and that finger length is a marker of your genes.” The ratio between the two fingers is fixed before birth and remains constant during life. As this is the case, the researchers suggest that examining finger length may help to identify talented individuals at an early, pre-competitive stage. No specific genes have yet been identified that control finger length. Experts believe it is likely that multiple genes are responsible.

So perhaps the digit ratio is also largely heritable. Can anyone find the study?

Brown gaucho & Tangled Bank #63

Our old friend Brown Gaucho is hosting Tangled Bank #63. I enjoyed his post, The importance of evolution in medicine. BG is a primatologist-turned-med student, so he knows of what he speaks. But, I do have to take some issue with this contention:

Anatomically and genetically, humans haven’t changed all that much in the past 100,000 years.

Yes, anatomically modern humans emerged over 100,000 years ago, but, that does not suffice to allow us to assume that genetically humans haven’t changed “all that much.” Of course, that depends on how you define “all that much,” but a supercharged immune system forged in the fires of the Eurasian pathogen pool & lactose tolerance don’t show up in the fossil record….

The god of death

One of the common ideas for why religion appeared is that it is a way of assauging fear of death. Chris of Mixing Memory reports on research which tests this hypothesis. Here is Chris’ summary:

In summary, then, when fundamentalists had their beliefs in Biblical inerrancy successfully challenged (i.e., they were presented with Biblical contradictions, and thus changed their minds about the existence of such contradictions), thoughts of death became more salient for them. So it does appear that religious beliefs, for fundamentalists at least, serve to minimize existential anxiety.

But this science, so not everything follows our intuition:

Strangely, the participants who were least likely to complete the stems with death-related words were the low fundamentalist participants who had read the passage about Biblical contradictions.

So for some religionists death and faith seem closely coupled, but not all religionists. At least if psychological experiments give us any window into the soul.

Brown gaucho & Tangled Bank #63

Our old friend Brown Gaucho is hosting Tangled Bank #63. I enjoyed his post, The importance of evolution in medicine. BG is a primatologist-turned-med student, so he knows of what he speaks. But, I do have to take some issue with this contention:

Anatomically and genetically, humans haven’t changed all that much in the past 100,000 years.

Yes, anatomically modern humans emerged over 100,000 years ago, but, that does not suffice to allow us to assume that genetically humans haven’t changed “all that much.” Of course, that depends on how you define “all that much,” but a supercharged immune system forged in the fires of the Eurasian pathogen pool & lactose tolerance don’t show up in the fossil record….

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