Cultural differences may leave their mark on DNA
sciencebulletin.org
sciencebulletin.org
Epigenetics. It's the make-file for your genetic source code. Certain conditions can cause certain parts of your genetic code to be uncommented or commented-out. There are actually a number of different kinds of comments (histone modifications [1]) - each set of marks particular to a different compiler, in different contexts. And these comments/marks are copied with some fidelity to daughter-cells/children along with a high-fidelty copy of the underlying genetic code itself.
So the genes themselves are not being heritably altered, rather the recipe for which gene is where, when can be subtly changed. But again, the same mechanisms that permit the change in expression of those genes during a lifetime can be subsequently changed in the next just as easily.
In this way you can store the code for some trait or capability over many generations without having it always be running. It can manifest itself in individual organisms as having very different phenotypes even with the same underlying code.
A snapshot of my mental model of epigenetics (warning: epigenetics/histone modifications are not my particular field of study): "The methylator slides along DNA to methylate histone tails at location 32 of histone 2 while in simultaneous competition the demethylator demethylates methyl groups of histone 1 at locations 4, 12 and 18 under most conditions, or location 32 of histone 2 IFF it is within three histones of an acetylated histone which itself has its acetylation competing with a deacetylator - constantly. And if a certain set of marks occur appropriately in combination, a set of neighboring histones wrap up and hide themselves and their DNA - preventing its hidden DNA from being used in that cell until some other mechanism can unwrap that section. Oh, and (most of) those marks are copied to children/daughter cells right along with the copying of DNA."
Because it's so fickle, non-deterministic, and tangled (unlike it's DNA counterpart) it's actually pretty hard to study and is currently (like this afternoon, down your street) a topic of a significant amount of cutting edge research. As the wikipedia article above shows, the 'Histone Code' is still a work in progress, and it now appears unlikely that there is a 1:1 relationship between this chemical mark and that effect, very much unlike the very nice deterministic relationship we found between DNA->RNA->Protein.
One common change I've read about that bubbles up to normal life is the capability of nicotine to affect histone acetylation. It seems to rapidly alter histone modifications so as to make other habits/actions more addictive [1] (precisely in a way that we now know THC does not - the original 'gateway drug' mis-extrapolation).
[1] https://www.nih.gov/news-events/nih-research-matters/why-nic...
MANY blacks in the Americas and Europe have significant European DNA. For example, even though my family identifies as black, my mother and her siblings are almost 50℅ European according to DNA tests.
How does this factor in when making medical decisions based on assumptions regarding race?
Outside of Africa, that's probably to be expected.
I too am "black", with two "black" parents but my mother had red hair and green eyes. My son has blonde hair and blue eyes.
Racial identity translates very poorly into actual population genetics, let alone epigenetics.
But the new data showing that a large fraction of epigenetic signatures of ethnicity reflect something other than ancestry suggests that abandoning the idea of race and ethnicity altogether could sacrifice a lot of valuable information about the drivers of differences in health and disease between different communities."
The study shows that abandoning the idea of ethnicity could sacrifice information, but it still seems to indicate that genetic ancestry is more useful than race. Why does the article seem to conflate the two?
Also if culture impacts genetics then the idea there are races is clearly not the case, but rather loosely organized behavioral groups that can change in whatever direction their common culture takes them next.
All of the conclusions being drawn about the implications of this for your hobby-grudges about politics are beyond inane
The Atlantic had an article about exactly the kind of thing you're taking about, and how this kind of pseudoscience is being pushed by neo-nazis and the alt-right: http://www.theatlantic.com/amp/article/510962/
Nothing in the article is racist, nor is anything in my statements. Please take your ad hominem elsewhere.
At the time of this article only two of the many subthreads related to this article had descended into politics and name-calling. One was initiated by your very own unsubstantiated attack on "identity politics". The other (considerably less favourably-received) post was claimed the notion of a social element to race that was the work of "lunatics and agitators seeking to attack and disrupt western society" and argued the researchers were doing themselves and society a disservice by engaging with it. Remind me who it was that's putting a negative slant on useful medical research again.
As a side note, when I started my thread there were more than 60 upvotes on the article and no comments. At least there's a discussion.
“These data suggest that the interplay between race and ethnicity as social constructs and genetic ancestry as a biological construct is more complex than we had realized,” said Noah Zaitlen, PhD, a UCSF assistant professor of medicine and co-senior author on the new study. “In a medical context both elements may provide valuable information.”
Setting aside the fact that this is such a touchy issue that the authors are carefully couching their language, it looks like there may be ways in which this new information can help people by tailoring medical treatments. I'd love a ELI5 explanation of this if I'm somehow misunderstanding, but the conclusion I formed seems to be supported by the article to my reading of it.
Note, I'm not taking a hardline stance. That's why I said "race is not just a social construct" in my conclusion.
The classic example discussed is a study of children born during a famine. Children born during famine are going to be smaller than normal, but it was found that their children and grandchildren would be born smaller than normal, even though the famine has long since passed. This change has been attributed to a particular methylation pattern that was passed down.
It's known that things like exposure to famine and abuse can change methylation patterns, but this study suggests that non-traumatic things like your cultural upbringing can affect methylation.
It seems like the debate we're having is a rehash of nature vs nurture, where it seems like the new research indicates nurture can affect nature for future generations through gene expression.
I don't think there's more genetic diversity among Bantus than the rest of the world combined.
Not population geneticists. Africa in those cases == sub-Saharan African people, not just Bantu.
I am a layman who knows next to nothing about genetics, but a bit about Africa, and I would not consider the two peoples to be in the same race. They look completely different - which is what most laymen use to determine race, isn't it?
The study does not compare other groupings of people who share a common environment and the influence on their epigenetic markers.
It says nothing about identity politics.
1. Race as a social construct. It does exist in that capacity - as an extreme example Irish were not considered "white" in America (google for some "hilarious" images from "back in the day").
2. Race as a biological reality. This is a touchy subject for a variety of reasons. But that doesn't mean that well documented taxonomic differences between human races are "fake". They do exist and are more than "skin deep" - things like bone density, cranial capacity, maturation etc etc. Ask your dentist if he can tell by looking at someone's jaw x-ray whether it belongs to an east asian or sub-saharan african.
But even so the human genome is not continuously distributed, even if the difference is linear with distance, simply due to the fact that humans are not continuously distributed geographically. You can't handwave oceans and mountains away.
The main criticism of clustering is that the hierarchy of clusters that you obtain depend on the distribution of your samples, and that we currently do not have a good uniform sampling of human DNA. In short clustering can tell you reliably if someone is Irish or Italian, but may falsely identify the french as italian if there are not enough samples for french people.
Race is not just a word for different breeding populations of humans. The dilution of its meaning into something so innocuous is ahistorical, in fact it contradicts what was claimed to be the reality of race just decades ago. It's a political concept first and foremost.
No biological theory predicts races. Races are categories rooted in historical economic exploitation and domination that are a posteriori fitted with whatever truthy pseudoscientific justification is catchy at the time. Any categories of humans that biological measurements would come up with would hardly match racial categories. Perhaps the most racialized group that has distinct biological markers are Ashkenazi jews. However, the relation between Ashkenazi jews, Sephardic jews, and ethnic Arabs is very strong.
P.S. A review of the legal history of race in colonial America: https://sph.umd.edu/sites/default/files/files/Harris_Whitene...
I am hesitant to recommend it because I have not read much critique of its central points. But I think it's good.
to quote my own post - well documented taxonomic differences between human races.
Or are you talking about biological differences as they correlate with geographic locality?
"Heaps don't exist because you can't prove an ironclad boundary between heaps and non-heaps."
"Tallness isn't a thing because you don't have a firm, binary definition of when someone is tall."
Actually, there very much are.
I think what you're trying to say is that not all black people have all the "black people genetic markers," and likewise for other groups. This is true, but this is not necessary to distinguish well-defined groups.
Family resemblance is a philosophical idea made popular by Ludwig Wittgenstein
It argues that things which could be thought to be connected by one essential common feature may in fact be connected by a series of overlapping similarities, where no one feature is common to all.
That's not how I read it. My takeaway was that "race" is a social construct that can leave epigenetic markers. In other words, culture can affect physiology.
In other words harder sciences are proving that social sciences obsession with identity politics has hindered medical advancements once again.
I would agree that many in the social sciences create epistemological problems for ideological reasons.
Constructively, try not to see news as a chance to reinforce your existing views. Try and do the opposite. try to expand your world view.
My cousin is a bright, driven guy. There are reasons I distrust the western medical establishment.
The probability that a certain cultural difference induced mutation could be formed (given that there is no flow of information from a phenotype back to genotype) is something incalculable.
What might work for a bacteria does not work for humans due to, you see, fundamental differences in the reproductive system and development.
There are a few main principles from genetics 101 to consider before making any attempts of "doing science".
1. all mutations are *random*
2. there is no backward flow of information
3. environment does not alter DNA. random mutations do
4. propagating of a mutation is an extremely rare event
5. it takes *many* generations.
There is another fundamental principle: way to many hipsters in what they call "modern science".
What are you even arguing against?
Anything which contradicts with this principle is plainly nonsense - a product of unconstrained imagination.
BTW, any changes which could be propagated through the mother's body, the way some deceases do, would not get into the DNA. This is another fundamental principle which contributes to sustainability of life - it is about isolation and washing out of pathogens.
You are correct that the code of the DNA itself is not being altered, but there are other heritable mechanisms that affect the structure, capability and accessability of that DNA - i.e. gene expression, beyond the code of DNA itself. This enables capabilities encoded in DNA to be passed down to children without actually using them - or conversely, to enable certain latent capabilities under certain environmental conditions.
Life is a bit more nuanced than the dogmatic one-way flow of information we teach as 'the central dogma'. It gains its complexity by always having an exception to its own rules somewhere at some point if it physically possible so, as to hedge against some change in conditions where that exception becomes more powerful than the existing rule. The exception may be inconsequential and of little benefit - until such time as it is not.
What you are taking about is an ordinary blood-borne sexually transmitted decease model (or a virus), and it has nothing to do with genetics (gene expression is a developmental topic), so there will be no "marks on a DNA" in principle - it does not work that way.
There, however, could be some certain proteins bound to DNA, but it is a not a genetic but biochemical (pathogenic-like) change. Those proteins could be treated as markers.
The propagation rate of such proteins is still limited by the generation time, so any connection to cultural differences is nonsense.
So, it is not genetic, there is no marks on DNA, it is not cultural. Period.
The methylation of histones (one type of epigenetic modification) which is a chemical modification of a protein bound to DNA is absolutely a heritable modification, and thus is technically a component of your 'genetic information' - but it itself not DNA. Regardless of terminology, a histone's chemical marks (and biochemical/phenotypic effects) are capable of being transmitted between mother and child, as well as between mother cell and daughter cell. If cell A switches from being heat-sensitive with respect to X, to no longer heat-sensitive with respect to X because a particular promoter was silenced by a histone modification, that phenotype will be passed down to the all of cell A's children (including gametes). That is absolutely a heritable genetic characteristic that has nothing to do with the editing or sequence of DNA.
This gets confusing because now our newer definition of gene, which was simplified to be synonymous with coding DNA, actually is more complicated.
Finally, gene expression is not just a developmental topic. Gene expression is not only what determines how you develop, but everything else in your body too. Gene expression is how your stomach determines how much enzymes to produce in a given hour, how your white blood cells determine which antibodies to produce in a given season, how your brain determines which neurotransmiters to produce in a given hour, how your skin determines how much pigment to make, how your beta cells determine how much and when to produce insulin, or how your body keeps track of its circadian rhythm, among everything else your body does. Gene expression is one of the primary mechanisms of bioregulation - especially for biological changes that take between a few hours and a few generations.
I do not understand your discussion of disease models/virus/pathogens. I'm unclear how those concepts are relevant here.
A hypothetical cultural example: A young boy is not well fed and eats a lot of a certain kind of hard-to-digest plant in place of meat. That young boy's own gene regulation may shift towards those enzymes which can break down that plant material and away from genes used to metabolize meat. Further, the entire metabolism may slow because of his cultural environment. It is very reasonable that those regulatory modifications to his own metabolism will be passed to his children. Not changes in the sequence of DNA, but heritable genetic regulation none-the-less. The effects are subtle, and can likely be relatively quickly overcome were the child to experience a significantly different cultural environment.
https://www.quantamagazine.org/20160105-supercoiled-dna/
Living DNA exists in complex coils, smothered in a jelly of inter-mediating molecules. It's quite messy and poorly understood! What is understood is that inheritance and expression of DNA information are absolutely non-linear.
Say some percentage of a population has tails. Then they start getting killed because they have a tail. A generation or two later, a much smaller percentage of the population will have tails. The likelihood of tails appearing in the population has decreased dramatically, due to culture.
How exactly, given that a generational time for humans is about 20 years?
One day, the 20 without tails kill the 5 with tails.
So at time=0, the prevalence of tails is 20%. At time=1 day the prevalence of tails is 0%.
The remaining members of the population may still have the genes to make a tail, but no one currently has a tail. If tails are a dominant trait, they won't. If tails are a recessive trait, a couple generations of killing babies with tails will do quite a lot to further diminish the prevalence of the trait.
I used a cartoonish model to starkly illustrate the possibility of the effect.
That doesn't mean I think reality would have such stark effects. It doesn't mean I think I've proved the effect occurs in reality.
https://www.gesundheitsindustrie-bw.de/en/article/dossier/ep...