I have often said that I tend to see "group selection" as a lesser evolutionary force when set against lower levels of evolutionary processes, e.g., "individual" or "gene" level selection. By group selection I do not mean pro-social tendencies, or the success of individuals who band together as a group, but rather evolutionary processes which can not be reduced down to a lower level of selection. In other words, evolution is acting directly upon the group as an emergent property of a collection of individuals. My skepticism toward groups selection is conventional and orthodox: evolutionary change induced by natural selection is, ceteris paribus, proportional to the variation in fitness correlated with heritable genetic variation. In other words, if genetic variation is uncorrelated with fitness evolution via natural selection will not occur. If there is no genetically heritable variation, then natural selection has no power. The classic problem with group level vs. individual level selection is that the former generally does not exceed the latter on the level of genes, that is, there is more within group variance than between group variance. Consider for example two groups, the Flemings and Walloons, the Germanic and Romance (French) speaking ethnic groups of Belgium. Though, on average, the Flemings maybe of fairer coloration (a genetically coded phenotype), it seems plausible that the variation within the Flemings and Walloons in hair color will exceed the difference between the two groups. In other words, on physical inspection alone one could not determine who was a Fleming or a Walloon with any great confidence, since the between group variance is dwarfed by the within group variance.
I use this example with a purpose: once the individual opened their mouth you would know immediately which group the individual belonged to, because language exhibits a more disjoint tendency. That is, while genes may grade into each other across clines, languages are more likely to exhibit sharp boundaries. To some extent this is an artificial construct of the modern age of nation states, many of the South Slav tongues for example are relatively recent creations which emerged out of the melange of mutually intelligible Slavic dialects. One could say the same for the Turkic "languages." But, though Macedonian may grade into Bulgarian, the chasm between Bulgarian and Turkish is sharp enough that the linguistic difference is a non-arbitrary marker. Language is a character which may be roughly homogenous in various groups, and yet exhibit a wide range over a short geographic distance. Many cultural forms can shift and evolve rather quickly, but human propensity toward conformity can also generate a surprising degree of group cohesiveness within a short period of time, resulting in the texture of cultural variation and similarity.
Now, let me illustrate what I'm talking about with a simple model.
Assuming that there are two populations, "Islanders" and "Mainlanders." The latter are very numerous, while the former are not. With the decline in sea levels a narrow isthmus has now opened between the island the mainland, so that the Islanders are now no longer strictly islanders. Over the generations of their separation from the mainland the Islanders have changed in both culture and genetics. At the time of the reconnection with the mainland the Islanders were genetically disjoint from the Mainlanders on gene 1, so that
Islanders = 100% allele A
Mainlanders = 100% allele B
Since the latter are very numerous the following treatment ignores them. The Islanders on the other hand are not numerous, but a small finite population. Assume that cultural barriers result in a 1% intermarriage between Islanders and Mainlanders. Over the generations allele A spreads to mainland and B spreads to the island...and so eventually there is hardly any genetic difference between the two groups, the lesser numbers of the Islanders results in their genetic absorption by the Mainlanders. But what about culture? We know cultural diffusion occurs, and such hybridization is obvious, but the transmission of cultural characteristics is not as definite and deterministic as that of genes. Each parent contributes 1/2 of one's genome, but, they do not always contribute 1/2 of one's cultural orientation. Consider for example the marriage between a high status individual and a low status one from different cultures, there is a possibility that the children would emulate the forms of the high status parent in preference to that of the low status one. Additionally, Judith Rich Harris has hypothesized that children are socialized and acculturated by their peers, in which case the "alien" parent's cultural influence might be minimal. In each generation the "native" culture may predominate and remain robust in its ascendance even as genetic differences melt away.
The implication here is clear: because culture and genes are transmitted and propagated somewhat differently the nature of evolutionary process may differ. Peter Richerson and Robert Boyd have developed a group selective model of cultural evolution taking into account culture's simultaneous plasticity and robustness, the propensity of humans to engage in social conformity combined with our adaptability. These models are important because they shed light on the utility of the common analogies made between cultural and biological evolution. Myself, I am cautious of making too close of a connection, but the devil is in the details.
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An astute analysis.
Some more thoughts:
Consider social groups as vectors of information transmission. Genes are only one part of this transmission; there are also, as you mentioned, memes (traditions, language, technology, etc.) as well as associated symbiotic species (domesticated crops and animals, opportunists - weeds and pests, gut flora, pathogens). Arguably, anthropogenically modified environments (other biota in the associated ecosystem, landscape and soil transformation, atmospheric carbon) and induced epigenes (epigenetic changes - directly heritable and not) are also part of this information transmission. (The niche construction concept overlaps with several of the aforementioned categories.)
Any of these categories of transmitted information can be analytically privileged. And all of these - genes, epigenes, memes, symbiotic species, anthropogenic environments - influence each other's expression and replication. Indeed, the 'group' is not just the set of human individuals comprising the social group but the entire symbiotic complex of all of these agents - manifested in the group's collective extended phenotype.
The important thing is that there be "evolutionary processes which can not be reduced down to a lower level of selection." Of course, that phenomenon does not preclude concurrent processes at lower levels of selection, especially at the individual level.
If most of these kinds of transmitted information - memes, symbiotic species, anthropogenic environment - are replicated as an integrated complex, but few or even none of the social group's genes are, the 'group' as defined as a collective extended phenotype could be said to have replicated. In addition, the persistence of these other features will provide a selective and instructive milieu that may promote certain genes (malaria resistance, lactose tolerance) and epigenes to appear in frequencies - or re-emerge anew - reminiscent of the originating social group.
I started a long response. Later, maybe.
The traditional social science doctrine up until recently was that biological evolution ceased when history (cultural evolution) began. That was excessive, but cultural selection has a degree of override or superimposition on genetic evolution.
It's complicated by the fact that a.) people can change cultures (e.g. Polish or Irish immigrants to the US) and b.) cultural/social/economic/political success is different than genetic success (e.g., Finns are genetic failures compared to Bengalis, Javanese, Tamils, or Egyptians, but culturally the more populous countries are unsuccessful.)
So you have two interlocked selection systems with complex and inconsistent interrelationships.
Examples of a genetically successful cultural groups are Amish and Mormons, both very fertile. The latter is also very economically/etc. successful. This is sort of like group selection, but not really the same thing biologists were talking about.
The latter is also very economically/etc. successful.
mormons "cook the books" a little in terms of their how successful they are. e.g., they inflate their numbers by including in "jack mormons," but the socioeconomic data tends to draw from middle class church goers.
Some of the Mormon economic success is the extraction of a tithe surplus which is dedicated to specifically Mormon purposes. IE, not an economic per capita success, but an economic group success.
May be, I'm a little bit too simple-minded ...
If I'm a traditional orthodox Jew and if I'm marry a traditional orthodox jewish woman BECAUSE of the same culture, language, religion, and a lot of similiar genes - you cannot explain that deed without taking "groups" into account.
I think Jews are a good example, because they live often together with many more Non-Jews than with Jews. So without "groups", only with individual selection, no genetic differences can be established between "groups", no IQ-differences etc. pp..
So the "group" PLAYS a role in natural selection, in human evolution. - ? And this, I think, is enough to say: There is more than individual selection.
- Please ignore this too simple-minded thoughts, if you think they are too simple-minded. And I will read with interest, what others have to say.
When behavioural sciences were young (K. Lorenz etc.) altruism was simply explained as favouring the interests of the group. Hamilton made a better explanation, he said for altruism you do not need to take into account groups.
But surely our every-day experience and a lot of scientific inquiry shows, that humans differentiate people along group boundaries. And if this lasts for some generations, inborn genetic differences will exist between groups - also concerning altruism.
So it seems very plausible to me, that SOME altruism can be explained on the individual level and SOME altruism can be explained on the group level. We know about a LOT of human groups that have experienced extinction. So: selection takes place - also on the level of groups.
If you have the ADHS-gene your altruism is of another sort than if you have NOT the ADHS-gene. If you have high IQ your altruism is of another sort, than if you have not high IQ. So: different human groups have different sorts of altruism. So selection can act. - ?
I haven't succeeded in formulating this to my satisfaction yet, but once society/culture enters the picture you have two parallel tracks of history.
1. Sociocultural history/evolution of acculturated groups
2. Biological history/evolution of individual biological organisms, which (for humans) all belong to groups.
Membership in social groups affects evolutionary success.
Genetic traits of the individuals in a group affect group success.
Some social groups are genetically well-defined (i.e., are kin groups).
Some social groups are not kin groups in any sense. E.G., a fair-sized New York City business which recruits sharp technical people internationally would be expected (odds-on) to have a mix of East Asians, South Asians, Caucasian Americans of various ethnicities including Jewish, and Europeans (including East Europeans). Other groups are not ruled out, though their absence would not be unusual.
Some social groups are not kin groups, though if they practice endogamy for a few centuries they will become kin groups. (An example is the Baba of Singapore, who are, or were, a well-defined somewhat endogamous group with its own dialect, descended from Chinese, Malays, and others, but no longer counted as either Chinese or Malay).