I think the answer about clear phylogenetic lineages in humans is that, by the criteria used in drawing such lineages within other species, NO, Tha answer is fairly simple, but details are given in the two articles by my colleague Alan Templeton, cited above. The basic issue is this: For a species to be clearly subdivided into sub-groups (sub-species, or the older term "race"), using molecular (mitochrondrial DNA) evidence, the lineages must be clearly distinguishable (not overlapping) and the territories occupied fairly distinct, with little or no gene-flow between them. For our nearest evolutionary relatives, the chimps, (genus Pan troglodytes, there are five clear sub-species, each with several clear lineages within each sub-species. Using the same molecular approach, humans show no clea lineages at all within the Homo sapies. Our groups form one big blur on a mt-DNA tree. The reason is that for the entire period of our evolution from Homo erectus, hominid populations migrated and interbred to a degree not matched by any other animal species. While different human geograpphic populations do have differences in their genetic make-up, these differences are minor when compared to true sub-species in other animals. It was pointed out long ago (Richard Lewontin among many others) that there is more genetic variation within any given geographic population than between any two populations.I hope this helps.

I think what you are talking about is the question of haplotype or haplogroup. You may have more luck finding the status quo in the literature searching for these terms and checking out the HapMap project for example.

http://hapmap.ncbi.nlm.nih.gov/thehapmap.html.en

I share your interest in the answer to this question.  I am thinking that the answer will be, "No, there are not, because modern humans ("us") are of VERY recent origin." Mitochondrial Eve, and all that.  Let the experts speak! 

Dear Phila, thank you for writing this ambitious (and potentially dangerous) question.

Unfortunately politics and historical racial wars have stressed scientists to take into consideration this question and particularly if the answer is yes.

As far as I know, phylogeography is a good tool to classify within a same species, groups of populations with several common historical processes of eco-geographical adaptations to their environment and consequently a partially common evolution. The biggest risk is if you try to classify these groups into formal catagories, and even if you exclude the term "race", it will be very difficult and dangerous for you because of political and philisophical subjectives point of view. Nevertheless, I think it is scientifically possible to classify eco-geographic evolutionary history of human groups, and the most prudent solution is to not use any rank for it (nor race, neither subspecies, or anything).

For me, considering there are several eco-geographical groups of human today is independant of any racial consideration, and consider we are "different" is not correlated with considering one is superior to another. We are just different and then, one is better than another in a peculiar situation but the another will be better than the first one in another situation. It is why diversity is good for any population of any species in terms of durability in the light of evolution.

In order to answer you, I remember a very interesting book (it was during the 80's I think, but I don't remember author nor title) which was classifying the current human species into 5 main groups :

- An Indo-European (Caucasian) one

- An African (Congoloid) one

- A South-African (Bushman) one

- An Asian-American (Mongoloid) one

- An Australian (Aborigine-Papuan) one

Of course at the contact zones of each group, introgression partially cancel the peculiarities and particularly after 1500 and the beginning of the globalisation.

I hope some people would like to answer without fear of controversy...

John Hawkes at U Wisconsin has a blog that often addresses questions in this area:

http://johnhawks.net/weblog/topics/news/finlayson-braided-stream-2013.html

Another good review: Antrosio, Jason, 2013. Race Reconciled Re-Debunks Race. Living Anthropologically, http://www.livinganthropologically.com/anthropology/race-reconciled-debunks race/. Last updated February 27, 2013.

I guess the question is, "is there any other concern, other than racism, that makes this question interesting?"  I don't know the answer to that question.  I kinda think not.  But perhaps the original questioner had something in mind.  

Nick  

Here are two interesting papers from the same author, explaining why he considers classifications into human groups (race or subpecies) are always subjective, because of the recurrent introgressions between past geographical groups, several time during our history...

I think the answer about clear phylogenetic lineages in humans is that, by the criteria used in drawing such lineages within other species, NO, Tha answer is fairly simple, but details are given in the two articles by my colleague Alan Templeton, cited above. The basic issue is this: For a species to be clearly subdivided into sub-groups (sub-species, or the older term "race"), using molecular (mitochrondrial DNA) evidence, the lineages must be clearly distinguishable (not overlapping) and the territories occupied fairly distinct, with little or no gene-flow between them. For our nearest evolutionary relatives, the chimps, (genus Pan troglodytes, there are five clear sub-species, each with several clear lineages within each sub-species. Using the same molecular approach, humans show no clea lineages at all within the Homo sapies. Our groups form one big blur on a mt-DNA tree. The reason is that for the entire period of our evolution from Homo erectus, hominid populations migrated and interbred to a degree not matched by any other animal species. While different human geograpphic populations do have differences in their genetic make-up, these differences are minor when compared to true sub-species in other animals. It was pointed out long ago (Richard Lewontin among many others) that there is more genetic variation within any given geographic population than between any two populations.I hope this helps.

Mankind is one and indivisible. All presumed differences are population conditional. Not in the sense of taxon-splitting. Even the so-called fossil human "species" could turn out to be time-populations, if to handle the definitional framework not so tight. The human being should be removed from the natural classification. With his coming came the awareness and culture, and thus was not a purely natural human evolution longer. Of course, the study of the connections is sexy and should also be operated, but without taxonomic consequences. No matter to what grade, such a thinking has always been a danger, and thus ethically highly questionable. My opinion only.

Applying taxonomic cladistics to extant H. sapiens is a touchy matter (as stated before) due to the scars we (as a species) bear as a result of atrocities made in the name of a (fictional) better/purer 'race'. Scientifically it is pointless because there is no H. sapiens sub-species. BUT cladistic statistics and expressions have been used to infer and explain genetic, geogenetic and morphological diversity of the species.

Although our species is fairly recent when compared to the time span of some extinct Homo (take H. erectus as a winner in this category), micro-evolution has had time to influence H. sapiens and the result is divergence of genotype and phenotype characterizing different human groups from different regions around the globe.

Genetics and discrete morphology have used different approaches and data processing techniques to prove the origin of our species in Africa and how/when it spread to all other continents (but Antarctica). As we migrated populations diverged beginning in the Paleolithic as the first groups ventured out of Africa. The more isolated in distance and time, the farther human groups are at genetic and morphological level.

Is it enough to separate sub-species? The answer is a big 'no' by all biological standards. Are we diverse? Yes, that's what made us the most prevalent species and the top of the food chain. Our brains, the use of tools as compensatory elements when facing harsh environments and our physical ability of adapt has triggered a process of diversification within our species that act above all on phenotypes. We look different, but at molecular level that difference is not significant to divide us.

Check the Genographic Project production. For the matter of morphological intra-species variety check the works of G. Richard Scott and Joel D. Irish (both here at Researchgate). Joel's work on African dentition is particularly interesting as he deals with the evolution of the human dentition in Africa and provides a great assessment of the discrete dental variation within the cradle of our species. As a matter of fact, for different regions you will find good literature on dental variety.

It would be awfully useful, I think, for the original questioner now to spell out the theoretical basis for his interest in the question. 

In my opinion the original question is a very interesting one. Very, very interesting. And the original questioner does not need to spell out nothing or explain more than he has already done. 'Much fear I sense in you'. And by the way... the human being removed from natural classification? That is really funny :)  

Waouh, Phila, you put the finger on a extremely hot point, of course. In just a few minutes I had an up-to-date information on this subject, considering that I got a Master's degree in Vertebrate Palaeontology and Human Palaeontology in Paris University in 1973 … Thanks a lot, folks. 

Dr. Sanchez,

I don't care WHO explains why its interesting.  I just want somebody to do so.  Can you help?  What better understanding of some fundamental problem in the physical, biological, or social sciences would flow from an answer to this question?  Put on your NSF grant reviewer's hat, here.  What would be the value to science of knowing whether human beings can be divided into one, two, three, four or more sub-specific taxa?

Thanks,

Nick

"What would be the value of knowing...?" - I suggest you go to the 2005 article by Templeton linked in a previous answer. Consider the figure comparing measures of within-species genetic variability among various species of widely distributed large mammals. The figure shows that there's a big range of values, and humans happen to be near the low end of the spectrum. That's an empirical demonstration that there is something to be known here, which is far more valuable than a dogmatic/mystical assertion that any particular species is "one and indivisible". Dogmatism and mysticism about human biology and history are problems, not solutions.

Hello All,

I feel like this discussion has gotten really philosophically, which is great, but here is what we know about human evolution. Tracing back the history of mtDNA (see work by D.C. Wallace), the Y-chromosome (see work by Underhill and Oefner), and some autosomal nuclear genes (see work by Templeton) have all revealed the same timeline of human evolution that matches up with anthropological evidence. From this we now know that there are three main 'lineages' all found in Africa from which one lineage radiated out off Africa ~50,000-75,000 years ago. These three lineages coalesce back to ~120,000-170,000 years ago, thus they are fairly recent and debunks the idea of sub-species and even makes us rethink race since most of the variation resides in Africa (this point of the topic can get very philosophic and relates more to social science). It should also be mentioned that there has been significant gene flow between lineages in more recent history and there has also been introgression from both Denisovan and Neanderthal historically which makes things even more complicated.

Now as Nicholas puts it, time to put on our "NSF grant reviewer's hat". Why should we care about tracing our evolutionary history back, who cares if there are one, two, three, or more lineages. For a long time medical research has focus on trying to find relationships between illness/resistance and different ethnic groups in order to help cure, treat, and predict illnesses. This has been historically very hit or miss since ethic groups may not represent genetic relatedness and thus can be erroneously grouped in a study. Take for example grouping all Africans into a single group. Now that we have a better understanding of our evolutionary history we have a better framework for hypothesis testing. Take for example examining associations between mtDNA haplogroups and diseases has revealed associations with Alzheimer’s disease, hypertrophic cardiomyopathy, retinal diseases, age-related macular degeneration, gastric cancer, renal cell carcinoma, and breast cancer just to name a few (see Blein et al. 2015 for an example and some background). By now understanding this along with associations with other parts of the genome we can better understand risks for certain diseases, find cares for others, and may even be able to personalize medical treatment. 

Hope this helps with the discussion.

Best Regards.

Dr. Scanlon,

Thanks for your response.  I agree the demonstration of a fact is more valuable than value laden assertions that might, or might not, be tainted with racism.  But not all facts are equal.  The value of the grant process is that it forces us to choose amongst the facts  we are going to pursue.  So, if you were trying to justify this project, by comparison with others, to a Federal Grants office, how would you argue fo its significance? 

Nick Thompson

Looking at the literature, there is evidence for population structure largely corresponding with geographical regions (using genomic SNPs: http://www.nature.com/ncomms/2014/140429/ncomms4513/pdf/ncomms4513.pdf and microsatellites: http://www.sciencemag.org/content/298/5602/2381.full), with differentiation between groups likely reduced by contemporary gene flow- facilitated I would think by modern travel. It should be noted that neither study show a particularly "strong" structuring between populations, with a large number of alleles being shared by all geographical regions, and most (93-95% in the latter study) of genetic variation was accounted for within populations (meaning essentially that individuals were only slight less different from individuals in other "populations" than to individuals within the same). 

It makes sense that we should see some level of "population structure" in humans, because with limited exchange between populations (limited gene flow) we expect increased divergence. Following the same logic, as human populations have increased gene flow (either by dissolving of cultural/ language barriers, or facilitated by increased capacity to travel, etc) than we would see a blurring of those boundaries. 

As for there being any evidence for taxonomic delimitation, no there is not. Not according to any definition of sub-species or species that I am familiar with. Although there is of course evidence for some limited gene flow between geographical regions (as would be expected given the distance, geographical barriers, cultural barriers, etc) we do not see divergence between groups sufficient to create taxonomic divisions, nor do we recover reciprocally monophyletic groupings within humans which would be indicative of distinct evolutionary lineages. As Dr. Allen pointed out, phylogenies inferred from mitochondrial DNA do not show clear distinctions, and as Max and others stated the Homo sapiens lineage has a very recent origin (relative to evolutionary timescales) such that we wouldn't really expect much phylogenetic distinction anyways. 

So what this all means is that in our short history as a species there have been some limitations to gene flow between geographical regions, but there are no significant phylogenetic groupings within the species which might be argued for elevation to some other taxonomic rank (e.g. subspecies). Reconciling any phenotypic differences among groups (e.g. pigmentation) requires an understanding that these differences came about very rapidly, according to the joint action of selection on those traits and random changes ("genetic drift") associated with factors such as small population sizes of founding populations in the several migrations out of Africa. 

SO, we see no evidence for sub-specific groupings based on a phylogenetic nor biological definition.

From an objective standpoint I find this to be an interesting topic of discussion, however I agree with others that often it is one with negative connotations- basically, why would it matter anyways?

Dr Bangs,

Thanks for this answer.  Exactly the sort of thing I was hoping for.  Very instructive. 

Please allow me to "push" the answer a bit. I see the negative value of this sort of research: it discourages us from trying to assign biological significance to our social categories.  But are there positive implications?   Does anything about the benefits of this sort of genetic analysis flow from sorting people into sub-groups?  Some people are prone to Alzheimer's (thank God for spell-checkers)..  How does assigning them to subgroups help us find them and cure them.  

I suspect you have some good answers to these questions.

Nick

As far as I know, in population biology there is a clear criterion regarding whether to denote one group of organisms as a 'race' or subspecies. When you try to discover the hierarchy of genetic variation and calculate Fst (or some related statistics), if the proportion of among-population variation is higher than 30%, you can denote these groups as different taxons (e.g. races). This is not the case with humans, even when you compare people from different continents.

Bilja

Hello Nicholas,

NIH has a great website to understanding why studying the genome of humans and tracing their evolutionary history is important. Below is one such example that I think shows how the interplay between these two can help with curing diseases.

"More recent examples include mutations in the CCR5 gene that appear to provide protection against AIDS. The CCR5 gene encodes a protein on the surface of human immune cells. HIV, the virus that causes AIDS, infects immune cells by binding to this protein and another protein on the surface of those cells. Mutations in the CCR5 gene that alter its level of expression or the structure of the resulting protein can decrease HIV infection. Early research on one genetic variant indicates that it may have risen to high frequency in Northern Europe about 700 years ago, at about the time of the European epidemic of bubonic plague. This finding has led some scientists to hypothesize that the CCR5 mutation may have provided protection against infection by Yersinia pestis, the bacterium that causes plague. The fact that HIV and Y. pestis both infect macrophages supports the argument for selective advantage of this genetic variant." ( http://www.ncbi.nlm.nih.gov/books/NBK20363/ )

Since then researcher tested why this mutant (called delta 32) is more common in some areas verses others and have found that this mutant appears to have first started to be common during the Bronze Age in Greece where prostitution is believed to have led to the spread of a HIV-like virus. Also it has been found to occur at a very low frequency in some tropical areas even though HIV is common in some of these areas. This lead to other researchers to test this mutant against different tropical diseases and found that it lead to a much higher risk of West Nile. 

For the last seven years or so this has lead to a the development of a treatment for HIV that as of last year has been shown to be very promising. Also by understanding the link of CCR5 gene and West Nile has lead to new research on finding a treatment for West Nile.

This does not mean that we are creating sub-groupings of people, nor would I ever suggest that, and nor is that even really possible since as Tyler and Biljana pointed out there has been significant gene flow such that there is very little among population total divergence. However, by understanding associations between diseases and the genome and tracing the rise and fall of variation against evolutionary history we can better understand resistance or lack there of which allows us to develop cures quicker, better predict side effects (like higher risk of West Nile in HIV treatment), and personalize medicine.

Hope this makes sense and answers your question. There are other examples out there this was just the first one I found.

(Also, so that I am up front, I am not a doctor yet, I am still a Ph.D. student in integrative biology working on using genomics to tracing historical and contemporary introgression in fishes, so this topic is not my expertise but I still find it interesting.)

Best Regards. 

Hello, Max,

I have spent a half hour writing an absolutely brilliant response to you wonderful note, and then, somehow, lost it to the InterSpace.  As a fisheries man, I am sure you know that it is always the big ones that get away.  After I pass through the 4 stages of mourning, I may try to recreate it, but in the meantime, please accept an inferior one.

I truly wish that I were a PhD student starting out on the boundaries of human genomics and human history.  I cannot imagine a richer vein to explore.  However, while your answer provides wonderful examples for why we should follow genomic threads through history, nobody, including the original question-asker, has provided any scientific justification for the original "grouping" question.  My suspicion is that there isn't any.  The question of whether are any natural subgroupings of human beings has bedeviled human biology for centuries because, outside of science, social conservatives kind of hanker for a positive answer, and social liberals kind of fear one.  But by arguin about it, both conservatives and liberals implicitly agree that the question is important, and that is where the big mistake is made.   Mine is a "curse on both your houses" argument.   My intuition, based on 40 years of study of the instinct problem in animals, is that the question of natural human subgroupings, freighted though it might be with ideological implications, has no scientific merit what so ever!  Nothing that has happened on this thread has shaken that intuition. 

Nick

Hello Nick,

I hate when I lose the internet after writing an answer that I have worked on for a while, this has happened a few times to me now.

The idea that there are well defined sub-groups is definitely not the case, there are no sub-species or anything even remotely like that. However, we are not one homogeneous species with a lack of structuring. The world is not so black and white, there is diversity and understanding the unique processes that have driven this rich evolutionary history is something I find interesting. To me the fact that we have such a diversity both genetically and culturally is wonderful. I know this can be freighting to think about sub-groupings but when reading some of these post they read like shutting down the idea of diversity in general and staying we are all the exact same and there is no support for genetic differences between populations and ethic groups and it is dangerous to even think any other way. I understand the dangers of classifying people into groups and I would not suggest that, but to think that there is no diversity in the world also seems dangerous to me. This is a dynamic topic and more knowledge to me always seems to be the best option.

Best Regards 

Recently, Frontiers in Genetics published a review paper in their Applied Genetic Epidemiology section that deals with most of the issues we have raised here head-on. The authors of this review say that it "demonstrates that, from a biological systematic and evolutionary taxonomical perspective, human races/continental groups or clusters have no natural meaning or objective biological reality. In fact, the utility of racial categorizations in research and in clinics can be explained by spatiotemporal parameters, socio-cultural factors, and evolutionary forces affecting disease causation and treatment response."

It is worth looking over and engaging with for those who are interested in the question I posed above.

Access the paper on PubMed: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4756148/

Maglo, K.N., Mersha, T.B., and Martin, L.J. (2016). Population Genomics and the Statistical Values of Race: An Interdisciplinary Perspective on the Biological Classification of Human Populations and Implications for Clinical Genetic Epidemiological Research. Frontiers in Genetics 7, 22. doi: 10.3389/fgene.2016.00022

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4756148/

There clearly are no categorical subdivisions in the human species. The genetic variation, at least, is clinal, meaning there are no sharp boundaries. To some extent this is true even for modern humans, Neanderthals and Denisovans. Modern Eurasians have about 2% Neanderthal genes, Melanesians up to 4% Denisovan genes, and some Central Asian (but not European) Neanderthals had modern admixture. Still, modern humans, Neanderthals and Denisovans are considered different subspecies or even different species. We may yet discover clinal midpoints between these extinct groups that have long since vanished. Non-clinal variation within a species usually arises when populations in the middle of a cline go extinct while those at the ends survive. 

Taxonomic categories such as species, subspecies, races, demes etc are descriptive constructs. They are defined for pragmatic reasons, for example when the task is to determine a fossil's relationship to living human populations based on osteology or on DNA in the fossil bones. Because of the clinal nature of genetic variation it makes no sense to aim for an all-purpose taxonomy of extant humans. There are of course geographic boundaries such as the Sahara Desert and the Atlantic Ocean that have historically restricted gene flow and therefore have sharpened boundaries between human populations, but the clinal nature of genetic variation is too pervasive. Therefore, races (or ancestral groups or whatever name researchers may prefer) should be defined ad hoc, depending on the nature of the research in which they are used.    

I want to congratulate everybody on this thread for an excellent airing of a tendentious topic. This has been an excellent demonstration of what RG can do to bring the world's scholars together to think about an important issue.

I owe everyone who participated in this discussion my thanks. I had asked this question because I was exploring a related topic which then became the subject of my Master's dissertation. The responses did show that this was still an interesting, and sometimes contentious, area to many, so thanks for that.

https://dx.doi.org/10.13140/RG.2.2.13186.99522

The answer is 'yes'