The anthropology of race and the discovery of a skin color gene, SLC24A5

MSNBC, NPR, and BBC News have run articles about a publication in Science run nearly two weeks ago about one of the genes that control skin pigmentation in humans. The source article is titled, “SLC24A5, a Putative Cation Exchanger, Affects Pigmentation in Zebrafish and Humans” and is led by a team of pathologists, molecular biologists, geneticists, and biochemists primarily from the Penn State College of Medicine.

Actually, finding SLC24A5 was an accident. The group of researchers were seeking cancer genes and stumbled upon pigment cells in zebrafish that resembled human pigment cells. The researchers were using zebrafish as the model organism for cancer genes, primarily because of their fast developmental cycle and the similarities in vertebrate genome.

SLC24A5 was first identified by the Penn State team and was not identified initially as a pigmentation gene, since they were on the prowl for cancer genes. As a gene, SLC24A5 is an acronym for solute carrier family 24, member 5, which lies in on the long (q) arm of chromosome 15 on postion 21.1, from base pair 46,200,461 to base pair 46,221,881 (Source), Entrez Gene has more on the specifics of the gene, however it should be noted that the gene is conserved throughout the lineage of Eukaryota to Metazoa, Vertebrata, Mammalia, Primates, Catarrhini, Hominidae, and onto Homo. Remarkably, the human and fish versions of the gene share nearly 70 percent of the same protein sequence!

Zebrafish Pigment and SLC24A5 geneIt was not until the the scientists drew tangents between the similarities in zebrafish and human pigment cells, which both contain granules called melanosomes. In specific strain of zebrafish, named golden for its ligher appearance, there are less melanosomes. Similarly, in lighter skin toned humans there are less melansomes which is due to a slightly different variation of the gene — one that codes the amino acid threonine. The reverse is for the dark, or wild-type, strain of zebrafish and humans with darker skin tones, which codes for the amino acid alanine — there are more melanosomes and a higher expression level of SLC24A5, as high as 38% in people of African origin. Whereas there is a 25% expression level of SLC24A5 in people of European origin. The image to your right, displays the wild-type zebrafish above has darker stripes than the golden zebrafish below. The insets show that the golden zebrafish has fewer, smaller and less dense pigment-filled compartments called melanosomes than the wild-type zebrafish.

The researchers then looked at two different human populations in which people with European and African ancestors had mixed relatively recently — African-Americans and African-Caribbeans. They found that, on average, people with two copies of the European version of the gene had the lightest skin. People with two copies of the non-European version of the gene had darker skin, and people with one copy of each version of the gene had skin color somewhere in between.

Ultimately this gene has deep roots into the debate over the validity of race. Personally, I was taught during my undergraduate career, that race is completely a social construct. And this is true for most anthropologists, who live by the mantra that there are more ‘differences’ amongst described races than between the races… meaning there is more prey area and things are not simply black and white. This opinion can be traced back to a 1972 paper by Richard Lewontin.

But this gene changes the foundation of that mantra, in my opinion. I wonder does a 7% difference in expression levels between SLC24A5 genes of peoples of African and European decent indicate somewhat a molecular indication different races? Especially when the difference is between 1 amino acid. Though, I must state that my curiousity will not go as far to follow conservative voice of Vincent Sarich and Frank Miele, in Race: The Reality of Human Differences, who say,

“racial differences in humans exceed the differences that separate subspecies or even species in such other primates as gorillas and chimpanzees” and that “race is a biologically real phenomenon with important consequences”

I still wonder the how this finding shakes the validity of race debate?

I also wonder how the identification of this gene also relates to the theory of human skin color varies with the amount of exposure to the sun’s ultraviolet (UV) radiation, or rather the more sunlight you receive the darker your skin will become. I was once taught in my Human Adaptability and Variation class, that

genotype + environment = phenotype

and won’t argue that if you are genetically predispositioned to be black that environment can or will change your phenotype, but I ask what role does environment have in the expression of this gene? Does skin not react to amount of sunlight to produce more melanin and therefor more melanosomes? Won’t people around the equator, and exposed to more sun, have darker skin tones than those farther from the equator and/or exposed to less sun regardless of how much this gene is expressed or regulated? How does acclimatization affect SLC24A5?

I guess this all boils down to what is race? Simply put is race solely a social construct, or is it biologically driven, or both? And why? Maybe it is another one of my rhetorical questions that can never be answered, but I’d like to know what y’all think about race, especially after reading about this gene.

28 thoughts on “The anthropology of race and the discovery of a skin color gene, SLC24A5

  1. What does the discovery of this gene have to do with the race debate, one commentor asks.

    Simple. There IS only ONE race! The human race. All else are variations of the original human template: the black African who migrated to all parts of the globe. Certain environmental conditions, mainly the last ice age, being the most severe climatic condition these immigrants face, and which isolated them for an unknown period fo time, contributed to genetic mutations and therefore changes in pheontype. But the basic template was and remains African. Race, as the term implies is a recent creation of the dominant culture. A term invented to make distinctions between groups based on skin color and societal status. It is essential political and cultural in origin, but has no scientific validity whatsoever.

  2. “Certain environmental conditions … isolated them for an unknown period fo time, contributed to genetic mutations and therefore changes in pheontype”.

    But that’s true of almost all species. The different phenotypes in other species are usually termed ‘subspecies’ or, less often ‘races’, but the situation is exactly the same as for the human species.

    And in other species too the actual boundaries between the various subspecies are often difficult to define, but the geographical extremities are still often quite different. Are you saying that the term subspecies “has no scientific validity whatsoever”?

  3. “But that’s true of almost all species. The different phenotypes in other species are usually termed ’subspecies’ or, less often ‘races’, but the situation is exactly the same as for the human species.”

    Hmmmm, TerryT, you have inadvertently agreed with Melaniki’s statement “Race, as the term implies is a recent creation of the dominant culture. A term invented to make distinctions between groups based on skin color and societal status. It is essential political and cultural in origin, but has no scientific validity whatsoever.” Subspecies is a term invented by humans to distinguish other life forms. Race, however, has been used for hundreds of years to infer a hierarchical order of worth in humanity. Being as knowledgeable as you are I am sure you are aware of the political discussions in Australia over the previous 210 years regarding our Indigenous peoples and how “Race” was used to justify the political authorisation of a slow genocide right up till 1967.

    I would like you to show us what decent scientist uses the word “Race” when discussing sub-species of any animal. I would also like you to tell us if you believe Sub-Saharan Africans, North African/Arabs, European Caucasion, East Asian Mongoloids are difference species or are they the same species with differences brought about through environmental changes.

  4. Michael,

    I’ll keep this short and simple: Race has not been defined exclusively on skin color and social status, the latter would be another term — “class.” Also, race, when used to describe differences, does not always infer hierarchical order. A separate social process digests these differences into hierarchy. Though, I will say that I don’t deny that the term has been used for that purpose in the past.

    Like I mentioned, race and its synonyms have been used to describe the structure of populations. When comparing a set of criteria, specifically biological traits such as haplotype frequencies, and the observation that the majority of group 1 is different from the majority of group 2 — we define them as separate, groups, categories, populations, ethnicities, race… etc. How these differences are interpreted and applied is a separate issue from the observation of differences.

    Kambiz

  5. Kambiz.

    Thanks for your comment. I’m not saying these things always happen but more often than not they do. My comment was indicating TerryT basically backed up what Melaniki was saying even though he apparently disagrees.

    Anyway in response. I wonder if people who are discriminated against because of their ethnicity (which can often be determined by things such as skin colour and physical features) would agree that “Race” does not infer societal status.

    “Though, I will say that I don’t deny that the term has been used for that purpose in the past.”
    Take a look at the current Presidential Elections in the US, “Race” is being used by people to infer Barack Obama is inferior to John McCain based purely on his apparent racial differences. There was even a lady, who McCain had to publicly rebuke, that said she couldn’t trust Obama because he was an Arab. Entire districts of the US are voting differently in this series of elections than in previous elections because Obama isn’t a “wasp”.

    Regarding “class” it is linked to Race in a few instances purely because in the past people considered to be of “inferior races” could not achieve a higher status and were denied basic human rights.

    The Holocaust, the German policy to eradicate the Slavs of an occupied Eastern Europe, Apartheid, the genocide of Tasmanian Aboriginal people, and the attempted genocide of mainland Australian Aboriginal people were all based on Race. In each of these things the dominant power inferred a lower social status on the victims based on nothing more than a racial designation.

  6. “I would like you to show us what decent scientist uses the word “Race” when discussing sub-species of any animal”. I’m sure I could find many if I was prepared to put in the time, however most biologists would agree that the two terms describe the same phenomenon, regional variation within a species.

    So when you ask, “I would also like you to tell us if you believe Sub-Saharan Africans etc. … are difference species or are they the same species with differences brought about through environmental changes” obviously I’d say they’re not different species but subspecies which are “the same species with differences brought about through environmental changes”, the same thing as races.

    Kambiz hit one of the problems you have with the term right on the head: “race, when used to describe differences, does not always infer hierarchical order”. Whenever it is used for that purpose we have to qualify the term by calling it ‘racial superiority’ or ‘racial discrimination’ (the latter usually justified by ideas of the former). At the risk of misunderstanding your tone I’d guess you disagree with this attitude (as do most of us at this site I’m sure) because you say, “in the past people considered to be of ‘inferior races’ could not achieve a higher status and were denied basic human rights”. But this developed through a inappropriate reading of human phenotypic difference.

    The fact that, “‘Race’ is being used by people to infer Barack Obama is inferior to John McCain” is a product of these sorts of belief and is not based on actual evidence.

    Maybe we could do away with the word ‘race’ and call regional human variations ‘subspecies’?

  7. “I’m sure I could find many if I was prepared to put in the time, however most biologists would agree that the two terms describe the same phenomenon, regional variation within a species.”
    Come on Terry, you know me by now, I’d be happy with just one ;-)

    “obviously I’d say they’re not different species but subspecies which are “the same species with differences brought about through environmental changes”, the same thing as races.”
    This to me does not make something a sub-species. There is not enough biological difference to justify this designation. Just because someone has different colour skin compared to me doesn’t mean their DNA structure is that different to mine to make them a different sub-species.

    “Maybe we could do away with the word ‘race’ and call regional human variations ’subspecies’?”
    As already discussed above, I don’t believe there is enough biological variation to even warrant the term sub-species.

    Kambiz’s discussion of this statement, ““race, when used to describe differences, does not always infer hierarchical order”, cannot be referred to as a problem. If this is really the case then its not a problem, is it? But how often does someone in the street (ie. normal person, normal life situation) say “he’s black”, or “he’s got different shaped eyelids”-“so they are a different Race to me” without thinking of the negatives of being like the other person? Come on Terry, you and I know these things make no difference to a person but the ordinary person in the street looks at someone slightly different and doesn’t think the way we do. There is a long history of seeing difference and equating that difference with inferiority.

    My basic point here is, the more science/society does to define difference the more it is used to separate various groups from the dominant groups.

  8. “I’d be happy with just one”. I seem to be unable to post links at this site but if you’re prepared to Google “chimpanzee” and “races” I’m sure you’ll find examples.

    “There is not enough biological difference to justify this designation”. You seem to over-rate the distinctiveness of most subspecies. A non-specialist would often have difficulty distinguishing them. Many subspecies are distinguished precisely by no more than slightly different colour. In other words their DNA structure is very little different.

    “There is a long history of seeing difference and equating that difference with inferiority”. Two separate statements. Our own eyes can usually tell us what part of the world someone’s ancestors come from. However equating such difference with “inferiority” seems to be a relatively recent development, and based on politics. In fact I’ve seen it argued the idea of racial inferiority developed in order to justify economic exploitation, or even displacement, of the various groups Europeans came in contact with as they spread around the world.

    “If this is really the case then its not a problem, is it?” It’s a problem in that many people “infer hierarchical order” where this is in no way justified.

  9. Kambiz, those links both point to the same page which, mentions nothing about “Race”.

    TerryT, Softpedia? Are you trying to tell me this is a publication which has alot of authority on the subject of genetics?

    ““There is not enough biological difference to justify this designation”. You seem to over-rate the distinctiveness of most subspecies. A non-specialist would often have difficulty distinguishing them. Many subspecies are distinguished precisely by no more than slightly different colour. In other words their DNA structure is very little different.”
    Not over-rating at all, I just don’t take this as an absolute certainty. After all these are man made designations aren’t they! What one scientist says is reality another will say no its not but something else is. As for DNA differences our DNA and the DNA of Chimps etc is incredibly similar, does this infer we are sub-species of another species? Not at all

    ““There is a long history of seeing difference and equating that difference with inferiority”. Two separate statements. Our own eyes can usually tell us what part of the world someone’s ancestors come from. However equating such difference with “inferiority” seems to be a relatively recent development, and based on politics. In fact I’ve seen it argued the idea of racial inferiority developed in order to justify economic exploitation, or even displacement, of the various groups Europeans came in contact with as they spread around the world.”
    One statement, I know I made it.

    Read up on Rome, Greece, and Persia and then tell try to convince me equating difference with inferiority is a new phenomena. Actually go further back to Egypt and look at its documented history and tell me that this is a new phenomena. “Race” as a designation within the Modern Human species was and still is a term used for Political means.

  10. First off. Would you like to define for us your version of the difference between ‘race’ and ‘subspecies’.

    “does this infer we are sub-species of another species?” I gather from that comment that you’re not a biologist. I’ve written an essay regarding species and suspecies at a blog called remotecentral. If you go there and scroll down the side till you come to a subject “Human Evolution on Trial – Species” I think you’ll be able to understand how it works. (Can’t seem to submit the comment while I have the link in). Within the next few days there’ll be another one there related to the subject entitled “Long Ago”.

    “One statement, I know I made it”. True. But you’ve mixed up two completely unrelated concepts.

    The political leaders of “Rome, Greece, and Persia” all had political reasons for justifying enslaving or conquering other ethnic groups. However the evidence shows that in general they were quite inclined to let what we would call ‘minority groups’ rise to positions of consequence.

  11. One of the problems with Taxonomy is that it encourages endless debates between lumpers and splitters. How much variation counts? Where to draw the boundaries between a species, subspecies, and a race?

    It is instructive to compare Cladistics to Taxonomy. We could avoid these endless and largely unscientific debates by focussing on degrees of relatedness instead of trying to define bounded groups. Imagine how a shift such as that would feed into public discourse about the differences between people…. No longer would there be separate Races, instead people who are more or less related.

  12. Tim, you got it in your first statement. People, this includes scientist, will never all agree on such things. I have already said this myself, but what do we get in reply, ” I gather from that comment” statements which do nothing.

    TerryT instead of blogging somewhere else, why don’t you ask Kambiz if you can blog here, that way I don’t have to chase you around the net. There is always something you can’t do or are not willing to do, so please don’t tell me to look somewhere else, especially after you send me softpedia as some sort of authority.

  13. “First off. Would you like to define for us your version of the difference between ‘race’ and ’subspecies’.”
    Race is a political term originally, and sometimes still, used to define people of different ethnicities. Sub-Species, is supposed to be a scientific term used to define different groups within a species. Humanity is Monotypic not Polytypic.

    As usual TerryT you mis-quote things. If you would kindly read back to thepart where I asked the question about Humans and Chimps being sub-species, you might just see I answered it with a “not at all”. Why do you mis-quote and twist words? What is your agenda?

    ““One statement, I know I made it”. True. But you’ve mixed up two completely unrelated concepts.”
    Only to someone who doesn’t know there history and isn’t watching what is happening in the modern world.

    “The political leaders of “Rome, Greece, and Persia” all had political reasons for justifying enslaving or conquering other ethnic groups. However the evidence shows that in general they were quite inclined to let what we would call ‘minority groups’ rise to positions of consequence.”
    And this happens everywhere else to, you might remember the Xhosa in South Africa have been running the country for over a decade now. In Australia we have had Referendums and allowed our own Indigenous Minorty to achieve many things. You seem to think that just because some past wrongs have been corrected that the minds of the masses are really all that different concerning “differences” in Humanity. I’m sorry to tell you but the events of Cronulla, Islington and my own town of Tamworth scream loud and clear that the Plebians of the world have a fear of “others” and use that fear to suggest “others” are inferior.

    To go further, why do some European gov’ts want to acquire the DNA of Gypsies yet not other peoples? They have all admitted its not for social benefits or for crime prevention. Why else would you single out one group if its not because of some fear and use that fear to keep a group down.

  14. First off, Michael, calm down.

    It may seem a monumental effort to make a couple clicks to ‘track’ down Terry, but it really isn’t that hard. So don’t act like drama queen about it.

    Secondly, you’re clearly expressing your own agenda as well. Race is simply not just a political idea. It is more than that. Race encompasses a lot of entities from ethnicity, biological variation, culture to political identity. Observations of genetic differences between populations as well as physical ones, are part of the population structure that defines a population as a population. Observations of cultural differences between populations also define the structure of populations. All of these are synonyms for race. To keep denying that race isn’t used in a multitude of applications, but rather strictly in political situations, is naive and ignorant.

    Now you and Tim can open up a relativist’s Pandora’s box by bringing up arguments that not all scientists agree upon everything, and feel you have a point. But you don’t. There are many scientists out there that are looking to see why people of African ancestry have such a high prevalence of kidney and Parkinson’s disease. Or why white people are not carriers of the cardio-protective haplotype. The most glaring example of genetic structure to a population/race can bee the Ashkenazi jew and they’re high prevance of Tay-Sachs and Cystic Fibrosis. I can go on an on about disease prevalence in populations, but I won’t. Neither Terry nor I have to answer your requests to show you decent research. You can do it yourself.

    Kambiz

    P.S. Correction on the political motivations of slavery in Persia — The Cyrus Cylinder, inscribed about 539 BC by the order of Cyrus the Great of Persia, abolished slavery.

  15. “First off, Michael, calm down. ”
    I am calm, so you don’t need to worry about that.

    “It may seem a monumental effort to make a couple clicks to ‘track’ down Terry, but it really isn’t that hard. So don’t act like drama queen about it.”
    Ah, now here we go. Kambiz, I have always respected the opinions of others, even when I don’t agree with them, but to go and insult someone is a low act. You own this website and I respect the service you are providing, but I do not respect someone who feels the need to insult others just because they don’t agree with them. I doubt after this post you will see me here again because this has become a place where opinions obviously cannot be discussed.

    “Secondly, you’re clearly expressing your own agenda as well.” No agenda, just discussing the fact that “Race” has been used in this way for thousands of years.

    “Race encompasses a lot of entities from ethnicity, biological variation, culture to political identity. Observations of genetic differences between populations as well as physical ones, are part of the population structure that defines a population as a population. Observations of cultural differences between populations also define the structure of populations. All of these are synonyms for race.”
    No one has said any differently, so I am not sure what your trying to say here.

    “To keep denying that race isn’t used in a multitude of applications, but rather strictly in political situations, is naive and ignorant.”
    I really hope this doesn’t refer to me. Because if it does it will be the second insult you have leveled at me in this post. Now to discuss this, I haven’t denied anything, I have pointed out that “Race” has in the past had, and in modern times as well, political connotations. Now to deny that this has occurred and no longer occurs in the general public shows a lack of understanding of the basic Human understanding of fear of others.

    “Now you and Tim can open up a relativist’s Pandora’s box by bringing up arguments that not all scientists agree upon everything, and feel you have a point. But you don’t.” Ah, but we do, and this is the point that shows science what it is. If we all agreed on something we wouldn’t have discussion. So your point in this case is mute.

    “There are many scientists out there that are looking to see why people of African ancestry have such a high prevalence of kidney and Parkinson’s disease. Or why white people are not carriers of the cardio-protective haplotype. The most glaring example of genetic structure to a population/race can bee the Ashkenazi jew and they’re high prevance of Tay-Sachs and Cystic Fibrosis. I can go on an on about disease prevalence in populations, but I won’t.”
    There are many scientist who also research why people in a certain region suffer from conditions such as Asthma. Yet this does not mean everyone from these regions are a sub-species or different “Race” to people in another region. As for Cystic Fibrosis there are districts in Australia that have a higher prevalence of it than other districts, this also does not mean these people are of a different “Race”.

    “Neither Terry nor I have to answer your requests to show you decent research. You can do it yourself.”
    I have never asked you to provide anything so please don’t say I have. I have asked Terry to show where he gets his information from because he plays people for fools and throws things into a discussion that he doesn’t believe. I apologize if asking someone, especially someone who say things he doesn’t believe, to clarify something with proof is upsetting.

    “P.S. Correction on the political motivations of slavery in Persia — The Cyrus Cylinder, inscribed about 539 BC by the order of Cyrus the Great of Persia, abolished slavery.”
    The point of this is? England abolished slavery to, but still went ahead and tried to exterminate entire groups of people because they were different. Until now no-one mentioned slavery. Why did you bring it into the discussion for correction when it hadn’t been mentioned?

  16. Michael,

    Just leave. You’ve clearly made an ass of yourself, so there’s no point in digging yourself into a bigger hole. You’re the first person I’ve had to ban, and I have no regrets. You’re no longer welcomed here.

    Kambiz

  17. Michael. just in case you return here:

    “I asked the question about Humans and Chimps being sub-species”. I have never said humans and chimps were the same species. What I said was that chimpanzees and humans (along with almost all other species) vary across their geographic range. In all species, other than humans, these variations are called either subspecies or races. For some reason we are unwilling to use the term ‘subspecies’ for humans. But you still haven’t said what it is you see as being the difference between a subspecies and a race.

    “Why do you mis-quote and twist words?” It seems from the above it is you who is doing that.

    “I have pointed out that ‘Race’ has in the past had, and in modern times as well, political connotations”. No-one here has disagreed with that. Any disagreement with you is that it is not always used in such manner.

    “he plays people for fools and throws things into a discussion that he doesn’t believe”. Once, regarding the southern coastal route out of Africa. And I certainly hit paydirt with that comment, didn’t I.

    “Until now no-one mentioned slavery. Why did you bring it into the discussion for correction when it hadn’t been mentioned?” I would have thought slavery (and genocide) based on race would be the ultimate end product of racial supremacy beliefs.

  18. man is created arbitrarily and without his desire.the problem may be compounded when one is born black,put in a world that is prejudice against black people.the answer to this suffering maybe the in coming of a modern messiah,who using science maybe able to change the skin colour as his client wishes.this may lend support to the notion that all men are created equal.if god has made a mistake we have a duty to correct it.keith cheng maybe that messiah!

  19. If you look at racism in nazi germany you’ll see exactly why race is totally political. Through a constant media assault of propaganda and brain washing Hitler created in the people’s mind this rift between germanic whites and jews. How many non-jews were forced to flee the country because they refused to adopt these views, or had to put up a facade of going with the flow? The people in germany weren’t inherently racist, but through political campaigning, it was infused into popular music, radio, newspapers, literature and films. I don’t think the average person is harboring unreasonable hatred for anyone different looking. I am more inclined to beleive that our media continues to make racial discrimination an issue as a way of keeping us divided and uncoordinated. If white, black, latino and asian people were all working together outside the boundaries of racism and ignorance it would be much harder to control any one group. To rally white people together what do they usually do? Blame social and economic problems on immigration, or “ethnic” street gangs, and instill fear of anyone strange or different looking. This is why even this long after 9/11 middle eastern people are continually harassed at airports and border crossings. This is why black people still have trouble getting a cab. This is why even though the president is black, 90% of every branch of government is white. Unfortunately for the ruling white elite in north america however indo-americans and asian americans and canadians are continually increaseing their presence in the population and this can’t go on for much longer the way it has been. Fortunately for all of us, soon we will see a change in the amount of racist white politicians as they are replaced inevitably by someone more indicative of the mixed racial background of their constituents. As a white male in north america however, my only hope is that we don’t equate the views of the politicians and media moguls with those of all caucasians. I like the fact that I live in canada and have as many native and asian friends as white, and we all like the same foods, tv shows, movies, music, etc… If stephen harper got on tv today and told me natives were the enemy of all white people I’d probably just turn off my television.

  20. Race is genetic(not a social construct) originating from an original source(blood line). Debate and confusion stems from bloodline to bloodline dynamic.

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