# DNA analysis and siblings **URL:** \ **Category:** Factual Questions\ **Created:** [January 18, 2018, 2:40pm UTC](https://boards.straightdope.com/t/dna-analysis-and-siblings/806906 "2018-01-18T14:40:38Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![rat\_avatar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rat_avatar/32/255_2.png) [@rat\_avatar](https://boards.straightdope.com/u/rat_avatar)\ **Post date:** [January 22, 2018, 5:26am UTC](https://boards.straightdope.com/t/dna-analysis-and-siblings/806906/41 "2018-01-22T05:26:08Z")
Bayes’ theorem should also be called out here. Let’s say that you have a genetics test that says that you have some trait that only happens in 1 out of 1000 people, and that the test is 99% accurate. Normally one would assume that this means that there is a 99% chance that you have this particular marker, when in reality you only have a 9% chance. [P(A|B) = ( P(A|B)P(A) )/P(B)](https://en.wikipedia.org/wiki/Bayes%27_theorem) With close siblings this can be dealt with through thousands of matches, but when it comes to assigning some form of cultural background it becomes problematic within just a few generations. Particularly if there is a small number of STRs which are ascribed to a particular sub-population like Ashkenazi Jews. It becomes even more problematic when only testing small portions of the genome. In some cases it can more closely resemble [Cold reading](https://en.wikipedia.org/wiki/Cold_reading) than scientific analysis. ---
**Author:** ![rat\_avatar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rat_avatar/32/255_2.png) [@rat\_avatar](https://boards.straightdope.com/u/rat_avatar)\ **Post date:** [January 22, 2018, 6:46am UTC](https://boards.straightdope.com/t/dna-analysis-and-siblings/806906/42 "2018-01-22T06:46:32Z")
Another link, showing how PCA (Principal Components Analysis), which is the main method used by these sites for ethnic assignment showing that the PCA is more effected by the sample size than the relatedness. Finally found a link that wasn’t surrounded by matrix math to help reduce induce anxiety levels 🙂 (but feel free to click back to the article for details) > **[A Genealogical Interpretation of Principal Components Analysis](https://journals.plos.org/plosgenetics/article/figure?id=10.1371%2Fjournal.pgen.1000686.g003)** > > Author Summary Genetic variation in natural populations typically demonstrates structure arising from diverse processes including geographical isolation, founder events, migration, and admixture. One technique commonly used to uncover such structure... (It is still a useful tool, but needs to be used within it’s limits) ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 22, 2018, 2:06pm UTC](https://boards.straightdope.com/t/dna-analysis-and-siblings/806906/43 "2018-01-22T14:06:39Z")
**John Mace** , if I’m reading that diagram right, it seems to be saying that bonobos are more closely related to western chimpanzees than either is to eastern chimpanzees. If that’s correct, then shouldn’t eastern and western chimpanzees be considered separate species, or bonobos considered the same species as western? ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [January 22, 2018, 2:20pm UTC](https://boards.straightdope.com/t/dna-analysis-and-siblings/806906/44 "2018-01-22T14:20:24Z")
> [@Chronos](#): > > **John Mace** , if I’m reading that diagram right, it seems to be saying that bonobos are more closely related to western chimpanzees than either is to eastern chimpanzees. If that’s correct, then shouldn’t eastern and western chimpanzees be considered separate species, or bonobos considered the same species as western? Figure 1A would imply that, but note that Figure 1B does not. That latter figure results from removing [homoplasies](https://en.wikipedia.org/wiki/Convergent_evolution#Cladistics) from the original data set. This is explained in more detail in the [full article](http://www.pnas.org/content/96/9/5077.full). ---
**Author:** ![Turble](https://avatars.discourse-cdn.com/v4/letter/t/8dc957/32.png) [@Turble](https://boards.straightdope.com/u/Turble)\ **Post date:** [January 22, 2018, 4:09pm UTC](https://boards.straightdope.com/t/dna-analysis-and-siblings/806906/45 "2018-01-22T16:09:00Z")
> [@rat\_avatar](#): > > … > > _Race_ is a purely a social construct, and is not a biological trait. This is a PC statement of the academic left and should not be taken as fact by those who have an interest in science. Curiously, those anthropology professors who teach it seem to see no logical disconnect when they proceed in the same class to teach students how to determine race from skeletal remains. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 22, 2018, 4:16pm UTC](https://boards.straightdope.com/t/dna-analysis-and-siblings/806906/46 "2018-01-22T16:16:48Z")
There is a biological phenomenon which might be called race, but it’s almost completely unrelated to what most people think of when they hear that term. Biologically, [this man](http://atlantablackstar.com/wp-content/uploads/2016/03/australia-aborigines-460.jpg) and [this man](http://cdn.cnn.com/cnnnext/dam/assets/171128161524-donald-trump-november-28-2017-01-full-169.jpg) are the same race, while [this man](https://upload.wikimedia.org/wikipedia/commons/thumb/0/0a/Zulud%C3%A4nzer.jpg/170px-Zulud%C3%A4nzer.jpg) and [this woman](https://img.purch.com/rc/300x200/aHR0cDovL3d3dy5saXZlc2NpZW5jZS5jb20vaW1hZ2VzL2kvMDAwLzA2OS8zOTUvb3JpZ2luYWwvYmF0d2Etd29tYW4tY2hpbGQuanBn) are different races (both from each other and from the first two). What most people think of when they hear “race” is, indeed, a purely social construct. ---
**Author:** ![Turble](https://avatars.discourse-cdn.com/v4/letter/t/8dc957/32.png) [@Turble](https://boards.straightdope.com/u/Turble)\ **Post date:** [January 22, 2018, 4:36pm UTC](https://boards.straightdope.com/t/dna-analysis-and-siblings/806906/47 "2018-01-22T16:36:13Z")
Let’s not get into a semantic argument. Are you redefining ‘race’? I think most people would think Trump is White or Caucasian and the other three are Black or Negro. I also think DNA testing or examination of their skeletal remains would give those same results. What race do you think most people would think they are? ---
**Author:** ![rat\_avatar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rat_avatar/32/255_2.png) [@rat\_avatar](https://boards.straightdope.com/u/rat_avatar)\ **Post date:** [January 22, 2018, 4:41pm UTC](https://boards.straightdope.com/t/dna-analysis-and-siblings/806906/48 "2018-01-22T16:41:32Z")
> [@Turble](#): > > This is a PC statement of the academic left and should not be taken as fact by those who have an interest in science. > > Curiously, those anthropology professors who teach it seem to see no logical disconnect when they proceed in the same class to teach students how to determine race from skeletal remains. Please provide a cite, here is mine. > **[AAA Statement on Race - The American Anthropological Association](https://americananthro.org/about/policies/statement-on-race/)** > > The following statement was adopted by the Executive Board of the American Anthropological Association on May 17, 1998, acting on a draft prepared by a committee of representative American anthropologists. \[…\] > [@](#): > > Physical variations in any given trait tend to occur gradually rather than abruptly over geographic areas. And because physical traits are inherited independently of one another, knowing the range of one trait does not predict the presence of others. For example, skin color varies largely from light in the temperate areas in the north to dark in the tropical areas in the south; its intensity is not related to nose shape or hair texture. Dark skin may be associated with frizzy or kinky hair or curly or wavy or straight hair, all of which are found among different indigenous peoples in tropical regions. These facts render any attempt to establish lines of division among biological populations both arbitrary and subjective. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 22, 2018, 5:05pm UTC](https://boards.straightdope.com/t/dna-analysis-and-siblings/806906/49 "2018-01-22T17:05:12Z")
> [@](#): > > Quoth **Turble** : > > I think most people would think Trump is White or Caucasian and the other three are Black or Negro. I also think DNA testing or examination of their skeletal remains would give those same results. You’re half-right: Most people would call Trump “Caucasian”, and the other three “Negro”. That’s precisely what “social construct” means: It’s what most people would say. But a genetic test would find that both Trump and the Australian were of the non-African race, and that the other two were of the Bantu and Pygmy races, respectively. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [January 22, 2018, 5:34pm UTC](https://boards.straightdope.com/t/dna-analysis-and-siblings/806906/50 "2018-01-22T17:34:50Z")
> [@Turble](#): > > Let’s not get into a semantic argument. Are you redefining ‘race’? While the human species can be divided into any arbitrary number of “populations”, the biological concept of race is synonymous with “subspecies”. There are no extant subspecies of humans. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [January 22, 2018, 5:49pm UTC](https://boards.straightdope.com/t/dna-analysis-and-siblings/806906/51 "2018-01-22T17:49:21Z")
Jerry Coyne is probably the world’s leading expert on speciation. His view: > [@](#): > > So when people say “race is a social construct,” they’re simply wrong. The only sense in which they’re right is that the designation of a finite number of easily-distinguished human groups (“races”) is a futile exercise, because we have differentiation within differentiation, making the whole exercise purely subjective. (You can, for example, distinguish subgroups of “Caucasians” within Europe, distinguishing those of Scandinavian from Italian ancestry simply by their genetic differences.) > > But that’s not what people mean, I think, by “social construct.” What I think they mean (since they are rarely explicit) is this: “There is no biological difference between human ethnic groups.” That’s just wrong. Or, more plausibly, they mean that groups designated by skin color alone as “races” show no other biological differences that co-segregate with skin color. But that’s not true, either. For one thing, skin color itself is based on genetic differences, ones that (as we’ll see tomorrow) probably evolved by natural selection. And skin color co-segregates with other physical characteristics, as in the group “African Americans.” Finally, there are genetic diseases, like sickle-cell anemia and Tay-Sachs disease, that are more prevalent in some ethnic groups than others, and that is useful biology to know. > **[Race as a “social construct”: trouble in Brazil](https://whyevolutionistrue.com/2016/10/17/race-as-a-social-construct/)** > > As I've written somewhere (but can't remember where), it always amused me that when I wrote an NIH grant application, I had to specify my "race" (black, Pacific Islander, white, Hispanic, etc.), but  ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [January 22, 2018, 5:58pm UTC](https://boards.straightdope.com/t/dna-analysis-and-siblings/806906/52 "2018-01-22T17:58:36Z")
> [@rat\_avatar](#): > > Please provide a cite, here is mine. > > [AAA Statement on Race - The American Anthropological Association](http://www.americananthro.org/ConnectWithAAA/Content.aspx?ItemNumber=2583) > [@](#): > > Physical variations in any given trait tend to occur gradually rather than abruptly over geographic areas. **And because physical traits are inherited independently of one another, knowing the range of one trait does not predict the presence of others.** For example, skin color varies largely from light in the temperate areas in the north to dark in the tropical areas in the south; its intensity is not related to nose shape or hair texture. Dark skin may be associated with frizzy or kinky hair or curly or wavy or straight hair, all of which are found among different indigenous peoples in tropical regions. **These facts render any attempt to establish lines of division among biological populations both arbitrary and subjective.** [my bold] This is a cite from anthropologists, not geneticists, and the first statement in bold is rather obviously wrong. _Correlations_ obviously do exist in the traits of human subpopulations, for example the prevalence of some genetic diseases in ethnic groups. The second bold statement is correct - there are no bright lines, none of these correlations are 100%. Any labelling of subpopulations is arbitrary. ---
**Author:** ![rat\_avatar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rat_avatar/32/255_2.png) [@rat\_avatar](https://boards.straightdope.com/u/rat_avatar)\ **Post date:** [January 22, 2018, 6:05pm UTC](https://boards.straightdope.com/t/dna-analysis-and-siblings/806906/53 "2018-01-22T18:05:13Z")
> [@Chronos](#): > > You’re half-right: Most people would call Trump “Caucasian”, and the other three “Negro”. That’s precisely what “social construct” means: It’s what most people would say. > > But a genetic test would find that both Trump and the Australian were of the non-African race, and that the other two were of the Bantu and Pygmy races, respectively. Chronos is alluding to the fact that Sub-Saharan Africa has the most human genetic diversity and the same has been shown to hold true for phenotypic diversity. Turbal: For any definition of “race” to be more than a social construct would require there to be more defined groupings in Sub-Saharan Africa than the entirety of the rest of the world. It would also need to explain why on average of 85% of genetic variation exists within local populations, ~7% is between local populations within the same continent, and only ~8% of variation occurs between large groups living on different continents. Craniometry and/or Phrenology may be taught at some level, but that is due to historical reasons and not scientific. But lets consider Trump as an example, some have claimed he is descended from Rurik. If his Grandfauther, Frederick Trump, was and had been in the Y hapologroup N1C1\* he may have been considered Finnish, and not German and could have been denied entry under the Chinese Exclusion act. It was only in 1908 that the Federal government lost a court case trying to deny citizenship to several Finns that that rule changed. Of course he is not Finnish and the claims were made by people who didn’t know that there is a that genetic connection with Rurik being Finno-Ugric, instead were trying to invoke the _viking_ claim. Note that at that time, Kallstad where his Grandfauther was from was also considered mostly “Alpine” and not “Nordic” and there was a huge movement in the US to stop the inflow of these undesirables, so he would not have been automatically considered white. Due to both improving conditions in Europe and the Great Depression the influx of these “less desirable” European populations slowed, and due to the red scare these populations were assimilated into the definition of “white” in the public’s eye. While I refuse to link to the text itself feel free to read Madison Grant’s “Passing of the Great Race” if you think I am making this up. > **[Madison Grant](https://en.wikipedia.org/wiki/Madison_Grant)** > > Madison Grant (November 19, 1865 – May 30, 1937) was an American lawyer, zoologist, anthropologist, and writer known for his work as a conservationist, eugenicist, and advocate of scientific racism. Grant is less noted for his far-reaching achievements in conservation than for his pseudoscientific advocacy of Nordicism, a form of racism which views the "Nordic race" as superior. > As a white supremacist eugenicist, Grant was the author of The Passing of the Great Race (1916), one of the most famou... While I can understand how it would feel like the claim that race is a social construct may sound like a political statement, the reality is that the entire concept of race was purely a political, non-scientific concept in the first place. The fluid nature of the definitions to meet political goals quite clearly demonstrates this but I am open to cites that show that there is a real, useful, biological bases for the common categorizations if you can provide a cite. Please feel free to open a thread in Great Debates if you want me to provide cites to all of the above claims. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [January 22, 2018, 6:17pm UTC](https://boards.straightdope.com/t/dna-analysis-and-siblings/806906/54 "2018-01-22T18:17:21Z")
rat avatar, we need to define not only “race”, but exactly what people mean by “race is a social construct”. If the latter means - “the colloquial labeling system for race is a social construct” - then yes, that’s correct, it’s arbitrary and sometimes wrong. But if it is supposed to mean “there are no identifiable human subpopulations with associated genetic differences”, then that’s wrong. That’s what biologists mean by race. > **[Race (biology)](https://en.wikipedia.org/wiki/Race_(biology))** > > In biological taxonomy, race is an informal rank in the taxonomic hierarchy for which various definitions exist. Sometimes it is used to denote a level below that of subspecies, while at other times it is used as a synonym for subspecies. It has been used as a higher rank than strain, with several strains making up one race. Races may be genetically distinct populations of individuals within the same species, or they may be defined in other ways, e.g. geographically, or physiologicall The term is... ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [January 22, 2018, 6:24pm UTC](https://boards.straightdope.com/t/dna-analysis-and-siblings/806906/55 "2018-01-22T18:24:00Z")
Broken link. > **[Race (biology)](https://en.wikipedia.org/wiki/Race_(biology))** > > In biological taxonomy, race is an informal rank in the taxonomic hierarchy for which various definitions exist. Sometimes it is used to denote a level below that of subspecies, while at other times it is used as a synonym for subspecies. It has been used as a higher rank than strain, with several strains making up one race. Races may be genetically distinct populations of individuals within the same species, or they may be defined in other ways, e.g. geographically, or physiologicall The term is... ---
**Author:** ![rat\_avatar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rat_avatar/32/255_2.png) [@rat\_avatar](https://boards.straightdope.com/u/rat_avatar)\ **Post date:** [January 22, 2018, 7:00pm UTC](https://boards.straightdope.com/t/dna-analysis-and-siblings/806906/56 "2018-01-22T19:00:07Z")
> [@Riemann](#): > > [my bold] > > This is a cite from anthropologists, not geneticists, and the first statement in bold is rather obviously wrong. _Correlations_ obviously do exist in the traits of human subpopulations, for example the prevalence of some genetic diseases in ethnic groups. > > The second bold statement is correct - there are no bright lines, none of these correlations are 100%. Any labelling of subpopulations is arbitrary. Outside of genetic diseases directly related to the base trait, like skin cancer and light colored skin, how many of these “prevalence of some genetic diseases in ethnic groups” actually have a cause that is related to the social construct of race? Consider heart attack rates and stress levels and poverty, or cultural differences in the acceptability to seek medical assistance. The fact that race is a \*social construct \* and not a biological trait does not limit or reduce it’s impact or potential value in using those _mythological, non biological_ groupings for tracking effect and for targeting efforts. Money is also a social construct, but that doesn’t mean that it is not a real factor in health or other outcomes in our world. One does not require a belief that there is some scientific biological basis for wealth for it to be a useful tracking method. But also note above how genetic diversity within a group is GREATER than the differences between distant groups, and ignore the most common “racial identifier” used today primarily developed in the area that is most likely to be segmented into one “racial group”. > **[Gene study shows human skin tone has varied for 900,000 years](https://www.newscientist.com/article/2150253-gene-study-shows-human-skin-tone-has-varied-for-900000-years/)** > > An analysis of genetic variation and skin pigmentation suggests that some particularly dark skin tones evolved relatively recently from paler genetic variants > [@](#): > > The new findings mean that relatively pale skin tone variants predate the appearance of our species and have been retained in some parts of Africa ever since. The problem is when someone takes a_social construct_ and then tries to apply that to a biological basis for truth testing. I apologize to the Mods and OP for derailing this thread, but the claim that “Elizabeth Warren just get a DNA test” and that would either reliably map to lineage with our current data sets, or have any meaningful implications is what I am responding to. Sure you will have some genetic markers that only relate to non-Africans due to factors like interbreeding with other non-human proto-human species, and sure there may be some mutations that are unique to small isolated populations. The point is that outside of conditions caused by the social implications of the categorization, it is not a reliable predictor for an individual who is a member of that group or a member of another grouping. A perfect example of this is the typical claim that African Americans tend to have higher incidences of heart disease, but that claim probably has more to do with social pressures than genetics, and this is backed up with the worsening outcomes for white american males compared to recent improvements in these minority groups. But once again feel free to provide scholarly cites that as a _biological trait_ that historical or modern racial associations are genetically causative outside of traits where the manifestation itself is the cause (light skin/cancer risk due to exposure) The only ones I can find that seem to show actual cause (outside of small isolated groups) are limited to the intra-species cross breeding with other proto-humans which seems to not have re-entered Africa. Were you specifically referencing Neanderthal, Denisovan and X inflow? Because as there is more genetic variation in Africa than the rest of the human population outside of those contributions I would be interested in cites that demonstrate your claim. But I have the feeling that confirmation bias leads one to overestimate the value of racial groupings as being a predictor here outside of these edge cases. ---
**Author:** ![rat\_avatar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rat_avatar/32/255_2.png) [@rat\_avatar](https://boards.straightdope.com/u/rat_avatar)\ **Post date:** [January 22, 2018, 7:05pm UTC](https://boards.straightdope.com/t/dna-analysis-and-siblings/806906/57 "2018-01-22T19:05:04Z")
> [@Riemann](#): > > rat avatar, we need to define not only “race”, but exactly what people mean by “race is a social construct”. If the latter means - “the colloquial labeling system for race is a social construct” - then yes, that’s correct, it’s arbitrary and sometimes wrong. But if it is supposed to mean “there are no identifiable human subpopulations with associated genetic differences”, then that’s wrong. That’s what biologists mean by race. > > [Race (biology) - Wikipedia](https://en.wikipedia.org/wiki/Race_(biology)) Please show that use with humans in modern science. This is petitio principii (assuming the initial point) as this is exactly why the term was used by 19th and 20th century eugenicists and your Cite calls out this difference as a caveat at the top of the page. > [@](#): > > This article is about the biological taxonomy term. For the sociological concept, see Race and society. For the anthropological term, see Race (human categorization). For the RACE technique in molecular biology, see Rapid amplification of cDNA ends. If I have missed a modern usage of Negroid, Mongoloid or Caucasoid in modern science assigning humans to a biological taxonomy please share that cite. The general consensus is that there isn’t enough diversity to do so. Let me quote the link above’s statement on the Anthro usage of the term. > [@](#): > > Even though there is a broad scientific agreement that essentialist and typological conceptualizations of race are untenable, scientists around the world continue to conceptualize race in widely differing ways, some of which have essentialist implications.[17] While some researchers use the concept of race to make distinctions among fuzzy sets of traits or observable differences in behaviour, others in the scientific community suggest that the idea of race often is used in a naive[12] or simplistic way,[18] and argue that, among humans, race has no taxonomic significance by pointing out that all living humans belong to the same species, Homo sapiens, and (as far as applicable) subspecies, Homo sapiens sapiens.[19][20] But also note that Wikipedia clearly states that they are not a Scientific Journal, and that they error to common understandings over correctness. ---
**Author:** ![rat\_avatar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rat_avatar/32/255_2.png) [@rat\_avatar](https://boards.straightdope.com/u/rat_avatar)\ **Post date:** [January 22, 2018, 7:24pm UTC](https://boards.straightdope.com/t/dna-analysis-and-siblings/806906/58 "2018-01-22T19:24:10Z")
> [@Riemann](#): > > Jerry Coyne is probably the world’s leading expert on speciation. His view: > > [Race as a “social construct”: trouble in Brazil – Why Evolution Is True](https://whyevolutionistrue.wordpress.com/2016/10/17/race-as-a-social-construct/) Your cite would be more palpable if it didn’t resort to an ad hominem attack in the opening stanza. > [@](#): > > Leftist ideology that if you even talk about races But he is also incorrect in this claim: > [@](#): > > The only sense in which they’re right is that the designation of a finite number of easily-distinguished human groups (“races”) is a futile exercise, because we have differentiation within differentiation, making the whole exercise purely subjective. (You can, for example, distinguish subgroups of “Caucasians” within Europe, distinguishing those of Scandinavian from Italian ancestry simply by their genetic differences.) Note the PCA biasing problem I mentioned above, and the small differences here with only 67 populations. Warning PDF > **[PCA\_67\_World.pdf](https://drive.google.com/file/d/11PFNfcbtb3Ll8mqVLiFSoyO_342yYh3E/view)** > > Google Drive file. As a zoomed in version here is one with an “Italian” highlighted that you can’t see right next to Swedish as an image that debunks that political based cite. > **[dna2.png](https://drive.google.com/file/d/1F340MMKw30wOipVbM_M21cck0uJKJ4Ug/view?usp=sharing)** > > Google Drive file. And note that the differences here are absolutely tiny across that entire PDF. Can you provide a cite that isn’t trying to trump scientific methods to justify their political position? ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [January 22, 2018, 10:43pm UTC](https://boards.straightdope.com/t/dna-analysis-and-siblings/806906/59 "2018-01-22T22:43:32Z")
> [@Riemann](#): > > Jerry Coyne is probably the world’s leading expert on speciation. His view: > > [Race as a “social construct”: trouble in Brazil – Why Evolution Is True](https://whyevolutionistrue.wordpress.com/2016/10/17/race-as-a-social-construct/) Sorry, but the logic is lacking. There are biological races, but we can’t say how many there are. Or, we can say how many there are, but the number is arbitrary and two equally good scientist will often come up with completely different classification schemes. If he doesn’t know why race is said to be a social construct, I can only surmise that he doesn’t want to know. It’s a social construct precisely because there is no objective way to divide up human populations in any specific way. That makes any type of division subjective. Hence a social construct, as different societies will define race differently. in fact, the same society might define race differently at different times for political reasons. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 22, 2018, 11:11pm UTC](https://boards.straightdope.com/t/dna-analysis-and-siblings/806906/60 "2018-01-22T23:11:45Z")
As far as other traits correlating with “race” goes: Two of the four people I linked to share a fairly uncommon mutation affecting their digestive system. Unlike the vast majority of mammals, or even of humans, they’re able to digest lactose as adults. Can you guess, based on what you think their races are, which two they are? Here’s a hint: They happen to be the two tallest ones. [Previous page](https://boards.straightdope.com/t/dna-analysis-and-siblings/806906.md?page=2) [Next page](https://boards.straightdope.com/t/dna-analysis-and-siblings/806906.md?page=4)