Location: genes & culture
p-ter’s post about a new allele for lactase persistence is a powerful testament to the reality of gene-culture coevolution. These alleles which allow for lactase persistence have almost certainly spread over the last 10,000 years, and likely within the last 5,000. The fact that multiple alleles arose which exhibit disparate geographic distributions suggests that population substructure was generated in part by physical barriers (e.g., the mountainous massif at the center of Eurasia) which prevented selection from sweeping from deme to deme. This brings me to a note which I think is important to make: the same parameters which make a region amenable to a flow of information (culture) likely results in it being subject to repeated influxes of advantageous alleles from without. In other words, the rich get richer. Along trade routes come both cultural and genetic innovations. We’ve been discussing recent adaptive evolution and its likely acceleration toward the present, but if you read history you’ll also note that cultural change has also sped up a great deal. The society of ancient Egypt spanned over 2,000 years; obviously it was not static, but a farmer during the Old Kingdom would not have been particularly shocked by the customs & norms of the New Kingdom. In contrast, someone from 200 years in the past would be an alien among us.
Labels: culture
But someone from, say, 130 years in the past might be much less astonished. He knows about germ theory and evolution, so modern biology seems to be a reasonable extrapolation. He knows about the telegraph and photography, so that TV is not a shock. He’s seen trains so motor cars seem not too unfamiliar. He knows about automatic control, ……
It advances in spurts, does civilisation.
What bioIgnoramus said. Just to pluck an example out of a hat, I think someone transplanted from Greece circa 1000BC to Greece circa 400BC would be baffled by a few things.
I think someone transplanted from Greece circa 1000BC to Greece circa 400BC would be baffled by a few things.
the life of the average person didn’t change much. to some extent the same applies to bio’s comment; half of americans in 1900 lived in family farms. today around 1-2 percent do.
the rich get richer
i d’know.. i’m sure it sometimes works that way, but i’m also sure it often goes the other way. not having much water can lead to positive selection for genes that prevent dehydration. in our modern times, we’re relying a lot on computers to remember things for us.. isn’t someone without a computer being pressed harder to have a better memory?
i’d like to see some sort of empirical evidence (beyond individual cases like lactose tolerance) that the culturally rich usually get genetically richer faster than the culturally poor
“….But someone from, say, 130 years in the past might be much less astonished. He knows about germ theory and evolution…”
Actually, probalbly less than 1 % of the population, say, 130 years ago knew about germ theory and ewen less knew about evolution; the rest would be in a complete shock…
the rest would be in a complete shock…
there are still people to whom it would be a complete shock.
i’d like to see some sort of empirical evidence (beyond individual cases like lactose tolerance) that the culturally rich usually get genetically richer faster than the culturally poor
the native americans vs. world islanders is a good case. jared diamond makes the argument that their relatively small size vs. old worlders meant that they advanced more slowly. but the same probably works for disease resistance.
jared diamond makes the argument that their relatively small size vs. old worlders meant that they advanced more slowly.
sounds interesting, i’ll have to check that out. but how does it prove as a single case study the general trend that the genetically rich tend to get culturally richer or vice versa? i’m not doubting that it often works that way. it seems like some instances of cultural evolution would create a positive feedback loop with genetic evolution, but my intuition (perhaps falsely) tells me that in most other instances the cultural evolution would reduce selective pressures.. (why? because most every cultural advancement i think of seems like it would reduce positive selection for beneficial traits. as a basic example, weapons would seem to reduce, not enhance, selection for brute strength.)
As for Diamond, doesn’t he say in Guns Germs and Steel that he thinks the Australian Aboriginals (who are arguably the culturally poorest group of people on the Earth in terms of technological advances) were selected for higher intelligence than Europeans because of their brutish hunter-gatherer conditions? So my impression from reading that is that he’s someone who thinks environment/culture is the only major cause for the variance in human intelligence. Even if he’s wrong (which I’m sure is what almost everyone who writes or reads this blog thinks) such statements still suggest to me that he doesn’t think the culturally rich get genetically richer (in fact, quite the opposite).
in most other instances the cultural evolution would reduce selective pressures..
…Would not. Look at the culture as an addition to the environment; the more complicated (developed) this environment is, the stronger and diverse selective pressure it applies…. Culture does not simplify the environment – it extends it beyond nature and increases the pressure, since, first, it is more dynamic than natural environment ? hence, the rate of change in culture is higher than in nature?.a very influential environment, since the cultural traits often dominate natural. Instead of only one force, that you have to comply with in order to survive and replicate yourself, the nature, you have two forces ? nature and culture?.
(why? because most every cultural advancement i think of seems like it would reduce positive selection for beneficial traits. as a basic example, weapons would seem to reduce, not enhance, selection for brute strength.)
yeah, you’re model of evolution or selection isn’t right. there is no “beneficial trait” as such. all you need for evolution via selection to occur is this: heritability (that is, correlation between trait variation and genetic variation) and differential reproduction which tracks differences across a trait. you really shouldn’t be talking about “beneficial” traits in anything outside of a context specific manner in what increases reproductive fitness. what you’re talking about is relaxation of constraint for a function. e.g., as you note, people may get more gracile and less robust. this seems to have occurred with all agricultural populations. why would this be so? you can hypothesize that not only would be not need to be robust, but large robust people would need more calories and a diet more varied that typically found in an pure cereal diet, so they would be selected against on these grounds.
so, for example, if civilization collapsed and we became hunter-gatherers selection for many endemic diseases would disappear. the pressure to have particular MHC polymorphisms wouldn’t be there (though MHC would still be polymorphic for other diseases which can survive at lower densities). on the other hand, selection against myopia would kick in again. in other words, modern human societies and cultures are powerful selective environments. the movie ‘idocracy’ is an extrapolation of the traits which are ‘beneficial’ in 21st century amerika (e.g., low impulse control in regards to fucking).
As for Diamond, doesn’t he say in Guns Germs and Steel that he thinks the Australian Aboriginals (who are arguably the culturally poorest group of people on the Earth in terms of technological advances) were selected for higher intelligence than Europeans because of their brutish hunter-gatherer conditions? So my impression from reading that is that he’s someone who thinks environment/culture is the only major cause for the variance in human intelligence. Even if he’s wrong (which I’m sure is what almost everyone who writes or reads this blog thinks) such statements still suggest to me that he doesn’t think the culturally rich get genetically richer (in fact, quite the opposite).
1) diamond is not a geneticist. read his stuff closely and you see no formal insight here (example, check out his verbal exposition for why sexual selection explains races in ‘third chimpanzee’).
2) i think he’s lying. or, he’s specifically PC-proofing his argument by saying that these groups are smarter. not only do they do poorly on psychometric tests, but they also do well (aboriginals) on other tests that focus on visual-spatial from what recall.
i think australian aboriginals would be a group to look at in terms of being depauperate for adaptations for agricultural living. i think there’s a reason their lifespans are so short today (i suspect that lots of problems with european diseases is a major issue).
btw, besides lactose, amylase.
for the record, i think the decomposition of selection into natural, sexual and sexual is totally semantic. stuff that results in disparate fitness of alleles results in disparate fitness of alleles.
also, to make it explicit, i was also assuming
1) effective population size would be greater in areas which are interconnected. this increases the total number of potential positive mutants.
2) effective population size reduces the power of drift relative to selection, i.e., 2s is far greater than 1/2N. this makes evolution more deterministic.
3) i also assume that larger effec. pop relates to greater background variation for quantitative selection to operate upon. e.g., isolated italian villages would be driven toward homogeneity by inbreeding relative to a coastal part. the homozygosity means that no variation in quantitative traits might exist for some characters.
Diamond actually refers to people from New Guinea, not Australian Aborigines. Australian Aborigines have low scores on psychometric tests: I don’t know how people from PNG score. I’d like to, though.
what you’re talking about is relaxation of constraint for a function. e.g., as you note, people may get more gracile and less robust. this seems to have occurred with all agricultural populations. why would this be so? you can hypothesize that not only would be not need to be robust, but large robust people would need more calories and a diet more varied that typically found in an pure cereal diet, so they would be selected against on these grounds.
I haven’t read up on it, but I’m guessing I would almost surely agree with you that the combination of agriculture and a gracile body type is more fit than a robust body type without agriculture. What I’m speculating, though, is that if society collapsed, the gracile person would be less fit, because their genetic fitness relies on agriculture, a cultural innovation.. in other words, cultural evolution seems to have taken much of the burden off of genetic selection, so that people are more fit overall because of their culture, rather than their genes.
the movie ‘idocracy’ is an extrapolation of the traits which are ‘beneficial’ in 21st century amerika (e.g., low impulse control in regards to fucking).
that was a good movie. but the genetic implication seems to be that because we’re living in this safe corporate society where the culture provides for everyone’s basic needs, dumb people are not facing such strongnatural selection. that would seem to go against the view that cultural gains usually cause genetic gains.
that would seem to go against the view that cultural gains usually cause genetic gains.
“genetic gains” doesn’t mean anything (or if it does, explain what it means). move toward idiocracy might result in changes in frequency in drd5. evolution is change in gene frequencies. that’s all. nothing about ‘gain’ or ‘beneficial’ in any deep sense.
sorry i’m not using the scientific terminology here.. you obviously have a much better understanding of genetics than me, and i’m in the process right now of learning more.
anyways,
“genetic gains” would mean changes in gene frequencies that increase fitness. “cultural gains” would mean changes in culture that increase fitness. i would think that the increased fitness of gracile agricultural peoples over robust hunter-gatherers is mainly attributable to the formers’ agriculture (a cultural gain), not the fact that they’re gracile (a genetic adaption to agriculture).
ben, i’m in a hurry, so excuse the brevity
1) you should reade fisher’s genetical theory of natural selection. it will make these things clearer.
2) if the frequency an allele increases, and that increase is not due to stochastic processes (i.e., not random, but driven by selection of some sort), that is by definition an increase in fitness. in other words, you can’t separate evolutionary fitness from change in gene frequencies (though stochastic processes mean that change in gene frequencies does not entail evolution via adaption and increased fitness).
i would think that the increased fitness of gracile agricultural peoples over robust hunter-gatherers is mainly attributable to the formers’ agriculture (a cultural gain), not the fact that they’re gracile (a genetic adaption to agriculture).
you need to consider that lots of evolution occurs within groups (arguably most). that is, if a group of people took up agriculture then there might have been in situ selection for the more gracile because
1) they could survive famine more easily because of lower nutritional needs
2) there were other correlated responses with robusticity which resulted in negative selection once the necessity for robusticity was removed.*
in other words, the cultural change over time would result in selection for particular types within the group of agriculturalists.
* analogy, many tame domesticated animals revert to a ‘wild type’ morph once they go feral. think of the bland look of wild dogs. this is probably because once human selection is removed other selective pressures kick in and the population quick shifts to the new adaptive peak.
you can’t separate evolutionary fitness from change in gene frequencies
fair enough, but can’t you examine how much of the variance in fitness is attributable to culture vs genes by seeing what happens when people with certain genes are placed in different cultures, or by examining people in the same culture but with different genes?
in other words, the cultural change over time would result in selection for particular types within the group of agriculturalists.
we definitely agree on this point. but what i’m saying is that most of the variance in fitness between the average gracile agricultural individual and the average robust hunter-gatherer is due primarily to differences in culture (agriculture). on the other hand, the differences in fitness between a gracile individual in a non-agricultural society and a robust individual in such a society would be primarily genetic (body type).
therefore, it seems to me like the development of agriculture would reduce the degree of variance in fitness attributable to genes, and increase the degree of variance in fitness attributable to culture.
two sidenotes:1- i’m aware that the differences between the gracile and robust individuals in an agricultural society would also be primarily genetic. but i think the important point is that they, like such differences within a non-agricultural society, would be peanuts compared to the differences between individuals in agricultural societies vs. those in non-agricultural ones. 2- I assume we’re not talking about the earliest agricultural societies… many of the earliest ones, if i remember correctly, were actually not very fit at all compared to many of the hunter-gatherer and nomadic warrior tribes that existed around their time.