Thursday, January 28, 2010

Richard Dawkins. The price of collaboration?


One of my readers asks whether the renowned evolutionist Richard Dawkins has ever written on the subject of human races. Do they exist? And, if so, did this process of biological diversification stop a long time ago? Or did it actually accelerate when cultural evolution began to accelerate some ten thousand years ago?

Yes, he did address this subject six years ago in the essay “Race and Creation” (Dawkins, 2004). The essay starts off by acknowledging Richard Lewontin’s finding that human genes vary much more within races than between them. In fact, ‘races’ account for only 6 to 15% of all human genetic variation.

Yet this leads to an apparent paradox. According to Lewontin, the data tell us that any two human groups will overlap genetically to a high degree. Our eyes, however, tell a different story:


Well, suppose we took full-face photographs of 20 randomly chosen natives of each of the following countries: Japan, Uganda, Iceland, Sri Lanka, Papua New Guinea and Egypt. If we presented 120 people with all 120 photographs, my guess is that every single one of them would achieve 100 per cent success in sorting them into six different categories.

This paradox has been noticed by others. I remember one who claimed that ‘racism’ prevented us from seeing the genetic overlap between Danes and Congolese. Actually, the same overlap exists between many species that are nonetheless anatomically and behaviorally distinct (see previous post). It isn’t racism that creates the discrepancy between the data and our lying eyes. It’s just that most genes are weakly influenced by natural selection, especially the ‘structural genes’ that Lewontin and other population geneticists love to study. Such genes tell us very little about the strong selection pressures that have sculpted human differences in anatomy and many other traits.

It is fallacious to assume, as Lewontin did, that all genes contribute equally to real functional differences between populations, whether species or races. In fact, most genes have little selective value, being often little more than ‘junk DNA’. Even when a gene clearly is functionally significant, the difference between one allele and another may be like that between Coke and Pepsi. It is also fallacious to assume that genes with low selective value vary between populations in the same way as genes with high selective value. In fact, the more a gene has selective value, the likelier it will vary across a boundary between two different population, since such boundaries usually coincide with geographical/ecological barriers that separate different adaptive landscapes and, hence, different selection pressures.

Dawkins uses ‘Lewontin’s paradox’ to show that races do exist. But how relevant are they to recent human evolution? Hasn’t cultural evolution replaced genetic evolution in our species? On this point, Dawkins argues that the former has actually stimulated the latter. He draws an analogy with sympatric speciation in insects:


Some people think the initial separation has to be geographical, while others, especially entomologists, emphasise so-called sympatric speciation, meaning that the initial separation, whatever it is, is not geographical. Many herbivorous insects eat only one species of plant. They meet their mates and lay their eggs on the preferred plants. Their larvae then apparently “imprint” on the plant that they grow up eating, and they choose, when adult, the same species of plant to lay their own eggs.


… In the case of these insects, you can see that, in a single generation, gene flow with the parental type could be abruptly cut off. A new species is theoretically free to come into being without the need for geographical isolation. Or, another way of putting it, the difference between two kinds of food plant is, for these insects, equivalent to a mountain range or a river for other animals. I am suggesting that human culture—with its tendency to distinguish between in-groups and out-groups—also provides a special way in which gene flow can find itself blocked, which is somewhat analogous to the insect scenario I have just outlined above.


In the insect case, plant preferences are handed down from parent to offspring by the twin circumstances of larvae fixating on their food plant, and adults mating and laying eggs on the same food plants. In effect, lineages establish “traditions” that travel longitudinally down generations. Human traditions are similar, if more elaborate. Examples are languages, religions and social manners or conventions. Children usually adopt the language and the religion of their parents although, just as with the insects and the food plants, there are enough “mistakes” to make life interesting. Again, as with the insects mating in the vicinity of their preferred food plants, people tend to mate with others speaking the same language and praying to the same gods. So different languages and religions can play the role of food plants, or of mountain ranges in traditional geographical speciation. Different languages, religions and social customs can serve as barriers to gene flow. From here, according to the weak form of our theory, random genetic differences simply accumulate on opposite sides of a language or religion barrier, just as they might on opposite sides of a mountain range. Subsequently, according to the strong version of the theory, the genetic differences that build up are reinforced as people use conspicuous differences in appearance as additional labels of discrimination in mate choice, supplementing the cultural barriers that provided the original separation.

At this point, Dawkins winds up his essay, arguing that cultural differences in mate choice may explain many anatomical differences among human populations.

Fine. One point, though. Is mate choice the only human behavior that differs culturally? No, there are also differences in “languages, religions and social manners or conventions.” Wouldn’t these other differences generate selection pressures that likewise differ from one population to the next? And wouldn’t these selection pressures influence not only anatomy but also any trait with a substantial genetic component, including a wide range of behavioral predispositions, mental aptitudes, and personality factors? This would all follow logically from Dawkins’ reasoning. Indeed, he seems to hint at this when he states that “traditions” are no less part of our adaptive landscape than food plants. Having dropped the hint, he goes no further. End of essay.

It’s not as if I’m alone in making the above point. Claude Lévi-Strauss—hardly a rabid sociobiologist—brought it up in a lecture he gave in 1979:


The selection pressure of culture—the fact that it favors certain types of individuals rather than others through its forms of organization, its ideas of morality, and its aesthetic values—can do infinitely more to alter a gene pool than the gene pool can do to shape a culture, all the more so because a culture’s rate of change can certainly be much faster than the phenomena of genetic drift. (Lévi-Strauss, 1979, p. 24-25)

But Lévi-Strauss was never afraid to spell out what he thought. He was a public intellectual in the true sense of the word. In contrast, Richard Dawkins just hints, and hints, and hints … in the hope that someone else will pick up the ball and run with it.

Pathetic.


References

Dawkins, R. (2004). Race and Creation, Prospect Magazine (103), Oct. 23, 2004

Lévi-Strauss, C. (1985). Claude Lévi-Strauss à l’université Laval, Québec (septembre 1979), prepared by Yvan Simonis, Documents de recherche no. 4, Laboratoire de recherches anthropologiques, Département d’anthropologie, Faculté des Sciences sociales, Université Laval.

19 comments:

Tod said...

In 'Extended Phenotype' or 'Selfish Gene' (can't track it down it was in notes at the back I think) Dawkins refers to a study of the countries a persons grandparents were born in; the more diverse their ancestry the worse their health and fertility. He said that there are similar data for a wide variety of animals. Within races having ancestors from the same locality gives the best fitness was Dawkins' message, this makes Rushton seem mild and makes me think he is not too worried about offending the "Not In Our Genes' lobby.

there are also differences in “languages, religions and social manners or conventions.” Wouldn’t these other differences generate selection pressures that likewise differ from one population to the next? And wouldn’t these selection pressures influence not only anatomy but also any trait with a substantial genetic component, including a wide range of behavioral predispositions, mental aptitudes, and personality factors? This would all follow logically from Dawkins’ reasoning

It ought to but - somewhat ironically - Dawkins' weird psuedo-evolutionary concept of memes seems to have taken over his thinking and he spent much of his time in recent years banging away about religious conservatives.

To him religion is an "invalid vehicle model" and a sinister infuence to boot. As in most societies the 'forms of organization, ideas of morality, and aesthetic values' are dependent on their religion he can't draw the obvious conclusion without agreeing with D.S. Wilson

Ben10 said...

Don't worry, many collaborators turn resistants of the last hour.

But since we are back in the issue of race again, maybe it is time to give a precise definition of a "race". The problem is there is none. wikipedia gives no less than 14 definitions.
http://en.wikipedia.org/wiki/Species

A definition that seems to satisfy the Naturalist is the "Evolutionarily Significant Unit (ESU)":
"An evolutionarily significant unit is a population of organisms that is considered distinct for purposes of conservation. Often referred to as a species or a wildlife species, an ESU also has several possible definitions, which coincide with definitions of species."
To me, this definition looks like the definition of a 'population', a group of infividuals restricted into a define geographical area that looks different enough from other populations of different geographical areas.
Darwin would be happy with this, since it would allow the finches in the different island of the Gallapagos to be, indeed, different species.

But for a genetic definition, what is the precise amount of polymorphism that is required to reach the status of race/species and on which genes?
It agree that junk or non-coding DNA is not the best DNA to use since it varies so much in its significance. So, which genes to choose? That's a big question. Depending of the genes, most so called "species", as defined by naturalists, would not reach the status of "species" and would be instead called "variants", "populations", or "ethnies", but not species.

To start with a single genetic definition of species and use this definition with the preconceived idea that all humans are a single species might well put Lions, Panthera and Tigers into a single species as well, which would not make any sense.
Obviously, we said it before, the significance of polymorphism varies among Family, maybe even within a genus. Therefore there cannot be a single definition of species for all animal species. The solution would be to use a different set of genes for each family, maybe even each genus. If, in a given genus, the significance of polymorphisms varied itself greatly, then unfortunatly, no definition of species could be given within this genus based on a genetic definition (we would have to go down to the level of assumed 'species' to find the relevant polymorphisms, that is, we would have to assume that a species is different to prove that it is different...).

Assuming that a relevant polymorphism could be found in the genus homo, it would make sense to use a subset of genes within the 1 or 3% of genes that differ between homo and its closest relative, the pan genus (the chimps). If no meaningfull polymorphism could be found within homo, then no objective genetic definition of a distinct species could be given within our genus.
I suspect that it is exactly what would happen. We are already too far from the chimp to use it as an objective tool to mesure species within homo. We might have to sequence the genome of a closer, but definitively different, homo relative, like neanderthal, to find those objective criteria.

Eugene said...

Yes, that's part of the reason I became disillusioned with Dawkins and lost my interest in him. I wasn't aware of this article but I always sensed this reluctance to take on some controversial "right-wing" issues by a man who, based on his public appearances, can be broadly described as left-wing (as are his followers).

I have to say though, I can understand -- although of course don't agree with -- the fear of many people to take on this issue because it's been horribly abused in the past, particularly in recent history. After the horrors of WW2 and the Holocaust, there was a global repudiation of not just this particular topic, but indeed the whole evolutionary theory and genetic determinism took a big hit as well. To safeguard against the thinking that led to this catastrophe, the Social Sciences arose as the new "feel-good" way of describing human behavior: nurture-based, culture-based, and egalitarian. Hence B.F.Skinner and a whole generation of post-WW2 Social Scientists, including Lewontin.

But, to quote Dawkins, "just because something is comforting doesn't mean it's true." I wish a man of Dawkins' stature would follow his own advice. But maybe he happens to have other interests, and of course he's entitled to that.

In my own life, I'm keenly aware of the truth of many stereotypes surrounding ethnicities and races, but I don't talk about them publicly. Stereotypes, though denigrated by many, are an evolved human mechanism that is extremely useful because it captures some truthful elements. Both in my own ethnic group and other people's, I see consistent patterns of behavior that can be formulated objectively (without any subjective judgment, of course). And as a scientist and an objectivist, that really fascinates me.

Peter Frost said...

Tod,

I suspect he goes after religion because it's an easy target. As you point out, religion is not simply a meme whose interests are unrelated to those of its 'host'. Religion has co-evolved with its host, and to a large degree has become essential to the host's reproductive survival.

Ben19,

Ideally, variation at each gene should be weighted for its adaptive significance. For example, variation in 'junk-DNA' would have almost zero weighting. This weighted figure, for each gene, could then be used to judge the relative importance of within-race variation versus between-race variation.

In practice, such a calculation would be impossible. We don't know the adaptive significance of most genes. Even junk-DNA may have some significance (by altering the distance between a regulator gene and its target site).

Moreover, there is no objective framework for evaluating adaptive significance. Violent male behavior, for instance, is adaptive in non-State societies. Such males are more likely to attract women and have progeny. In State societies, we see the reverse: violent males are more likely to end up in prison and be ignored by high-quality females.

Peter Frost said...

Eugene,

It's commonly believed that the race concept fell into disgrace after WWII. In fact, it was widely accepted in anthropology textbooks until the early 1970s. Lewontin's 1972 paper was key to the rise of race denialism, but there were a lot of other things going on at the time. In particular, this was when overt efforts were made to expel 'racist' professors from universities. In many cases, the professors were no more racist than Mother Theresa, but the 'chill' effect was real.

Eugene said...

Question for Tod... you wrote:


the more diverse their ancestry the worse their health and fertility.


I've actually read articles suggesting that a diverse genetic background is healthier because it builds up the immune system against a greater range of diseases... In other words, someone of mixed ancestry (like Barack Obama) would be overall healthier and have a better immune system.

But of course, if that were truly the case, people wouldn't be seeking out mates who look like them (which has also been suggested by science).

So, do you have any further info on this? Any opinions? Thanks

Tod said...

From what I have read the human studies came to the conclusion that it didn't make any difference, wonder what happens down the line. I'm not the person to be asking though.

Ben10 said...

Peter, I understand your comment, but what is a human race? I assume that human race = species or subspecies. The subspecies classification is already very unclear, see wikipedia. Whatever definition is choosen, it must lead to an objective test, based on mesurable genetic data, like the homology between critical genes of evolutionary significance in the homo genus. The test needs controls, it must put the chimp and earlyer hominids out of Homo sapiens species and it has been suggested that Lewontin's techniques, applied to canidae, would fail to put dogs, wolves and coyotee under different species. If he can't see the difference between a siberian wolf and a Terrier, is there a chance that Lewontin could have seen the difference between a neanderthal and a sapiens? if not, everything further is irrelevant.

Now, if we are not talking about species, what are we talking about?
For what I understand, genetic markers such as haplotypes have nothing to do with the issue of species and taxonomy. They are just tools to reveal ancestrality and some markers should be able to go down to our ape ancestors and further to our fish ancestors, which of course doesn't mean that human and fishes are the same species. But since haplotypes also cluster with populations, it's likely that most people assume that human races = populations, which obviously exist. But why the fuss then ?
Does Cavalli Sforza deny the existence of human populations ?

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Average Joe said...

In other words, someone of mixed ancestry (like Barack Obama) would be overall healthier and have a better immune system.

But would apparently be a mediocre president. Seriously though someone of mixed ancestry might actually have a weaker immune system since they might inherit genes from one parent that conflicts with those from the other.

Peter Frost said...

Ben10,

'Races' and 'species' are points on a continuum of increasing reproductive isolation and diverging selection pressures. We usually define a species as a population that cannot interbreed with another population. The reality, however, is a lot fuzzier than most people imagine. Many species can, in fact, interbreed and produce fertile hybrids. It then becomes a matter of deciding whether the amount of interbreeding is 'significant'.

On this point, biologists will argue back and forth. Many 'species' have been downgraded to the rank of 'subspecies', only to be declared 'species' again. Neanderthals are a case in point. There probably was some intermixture between them and modern humans, but it seems to have been minimal.

In reality, species are a lot more open to gene inflow than we think. The human genome even has admixture from viruses.

Anon,

The pictures seem to have attracted more readers. Thanks for the tip!

ben10 said...

so, 'race' is between 'populations' and 'subspecies', correct?

Ben10 said...

Well, correct me if I don't understand correctly.
Apparently, it is possible to quantitatively compare the genetic diversity of different species. What follows come from John Goodrum blog at:
http://www.goodrumj.com/RFaqHTML.html
I pass on the 75% rule in:"Q: How genetically differentiated are human continental populations (the major races) from one another compared to populations of other species?". This rule is based on morphometry that applies better for naturalists.
The FST definition is more usefull.
I quote Goodrum's blog:
"FST = (Ht-Hs)/Ht where Ht is the genetic diversity within the total population, and Hs the average diversity within subpopulations".

And for example, from the table2, we can read FST= 0.155 for humans which is higher than most other animal species and comparable to dogs's breed (FST=0.154) It is mentioned that values over 0.15 are an indication of 'great genetic diversity'.

However, Goodrum warns us:"
we need to remember that an FST value based on one class of loci may or may not be representative of the overall evolutionary distinctiveness of the populations in question. For these reasons, values based on several types of loci should be considered before drawing any firm conclusions"

Yes, this is what we were talking before: the significance varies, and that's why it would make sense to only consider the loci that have shown evolution between homo sapiens and the chimps. Those famous 1 to 3% gene difference.

This said, and based on these numbers, Goodrum concludes that FST and other quantitative measurement indicate that, i quote:
"....humans display a subspecies-like population structure".
At least this affirmation is backed by data and numbers, apparently, human races ARE subspecies.

Peter Frost said...

Ben10,

The terms 'race', 'population', and 'sub-species' overlap considerably in meaning.

The term 'population' has a connotation of variability. It has become the preferred term because it clearly avoids any hint of essentialism.

The term 'race' can mean any clustering below the species level. I've even seen the word 'micro-race' for small isolates.

The term 'sub-species' is normally used for a population that can be identified by one or more visible traits.

Again, these terms overlap. Even the best geneticists will use them interchangeably.

I'm aware of Goodrum's work on this subject. He too is aware that gene loci vary in selective value and that, at any one gene, the alleles differ to varying degrees from each other in selective value. This leads to the paradox where two populations may greatly differ at the genetic level and yet seem virtually alike at the level of morphology and anatomy.

I'm not sure we can resolve this problem by looking only at those genes that differ between humans and chimpanzees. Over the past 10,000 years, humans have entered new environments that scarcely resemble anything that existed over the previous 3 million years. We have entered a completely new phase of evolutionary change. Frankly, I see no point of reference, no yardstick that could possibly measure the significance of these relatively recent changes to the human genome.

Anonymous said...

Ben10

Peter, I understand your comment, but what is a human race? I assume that human race = species or subspecies. The subspecies classification is already very unclear, see wikipedia. Whatever definition is choosen, it must lead to an objective test, based on mesurable genetic data, like the homology between critical genes of evolutionary significance in the homo genus. The test needs controls, it must put the chimp and earlyer hominids out of Homo sapiens species and it has been suggested that Lewontin's techniques, applied to canidae, would fail to put dogs, wolves and coyotee under different species. If he can't see the difference between a siberian wolf and a Terrier, is there a chance that Lewontin could have seen the difference between a neanderthal and a sapiens? if not, everything further is irrelevant.

Well, no, Ben, everything further is not remotely irrelevant. As a matter of fact it remains exactly as relevant. Just as the notion of "the color orange" remains relevant despite your likely struggle to define it in words.

If you really are as confused about race as you sound, maybe as stroll through Detroit after dark will help clear up some of your confusion.

Peter Frost said...

Ben10,

If we look at mtDNA, the genetic difference is less between the Neanderthals and some humans than it is between some humans. So even Neanderthals and modern humans show some genetic overlap. We should be able to repeat Lewontin's experimental method with nuclear DNA once the Neanderthal genome is fully reconstructed.

Anon,

You may have misunderstood Ben's point.

ben10 said...

"stroll through Detroit after dark will help clear up some of your confusion"

This is not about that. I know what you mean, but here, I was asking about the technical definition of the word 'race' in taxonomy, not in its common usage.

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