(I'll aim this question mostly at surgeons who may have done a lot of surgeries in different countries or countries with a lots of diverse ethnic groups.)

Lets take as examples a typical Norwegian and a typical Nigerian.

In terms of human anatonomy the outer differences are more obvious e.g. (on average)

  • White skin vs dark skin
  • Pointy nose vs broad nose
  • Thin lips vs thicker lips
  • Straight hair vs tight curly hair
  • Different skull shape
  • Height differences
  • Different colour eyes or eyelids.

In fact there is almost a difference in every external organ.

There are also some invisible differences such as propensity to sickle cell disease.

But what I hear less about is the differences (in general) between internal organs between populations. Some people even suggest that differences are only "skin deep" between human populations. Which I think goes against evolutionary theory. As why would natural selection stop at skin level? Also, there is a lot of research into skeletal differences but that's easier to do since we can look at a skeletons.

Therefor it seems fairly logical to assume that there would be fairly apparent differences in internal organs between these populations. (I hesitate to use the word 'races') i.e. as apparant as different hair types, or different nose shapes.

I don't mean that one population will have 3 kidneys for example, but I would expect that there would be an obvious shape or size difference between most, if not all internal organs, just as there is a shape, colour or size difference between most external organs.

Is there some research done on this, e.g. a catalogue of differences in internal organs morphology between different populations? Or is it taboo to even ask such questions perhaps?

One might say, "how would anyone know? Or care?" But, for example, a heart surgeon might find they need different sized instruments dealing with different people. Or surgeons from different continents might compare notes on anatomy. And anatomy textbooks based on just one population might not be representative. Surgeries working on one "race" might not work on others. e.g. if the heart wall was thinner or the colon was longer.

Another use would be if there was a victim and one wanted to guess the ethnicity of someone and the only evidence was an internal organ of some kind. Could it be done (without looking at the DNA?)

  • 4
    What prior research have you done to support this question?
    – Bryan Krause
    Commented Feb 22, 2020 at 0:07
  • 1
    "I would expect that there would be an obvious shape or size difference between most, if not all internal organs, just as there is a shape, colour or size difference between most external organs." -- Really? Why would you expect that? What have you found in your research to suggest that's true?
    – Carey Gregory
    Commented Feb 22, 2020 at 1:49
  • 2
    @zooby By no means am I picking an argument. What I'm pointing out is your question lacks prior research and makes unsupported claims.
    – Carey Gregory
    Commented Feb 22, 2020 at 5:56
  • 1
    Part of the problem is that if you ask "does X difference exist" it's easy to answer if it exists. If it doesn't then there is just no research because no one cares. I am personally confident that the individual difference in organ size vastly outweighs any racial difference but.. I also dont expect any citations to exist to say that. So when you give no research it's easy to ask unanswerable questions with no effort.
    – Bryan Krause
    Commented Feb 22, 2020 at 8:04
  • 4
    Anecdotal evidence from a surgeon would be a terrible way to answer this question.
    – Bryan Krause
    Commented Feb 22, 2020 at 18:29

1 Answer 1


why would natural selection stop at skin level?

The division of humanity into "races" was not natural. Yes, some (e.g. darker skin in sunnier locations) was natural, but for the most part it was the result of human intelligence and racism.

Genetic drift caused slight differences between isolated communities, but when those communities came into contact the interbreeding that would normally occur with non-intelligent species tended not to happen.

People tend to favour those that look more like them and to fear those that look different, so it's natural to choose familiar looking mates. Beautiful people had more children than did ugly people. Over time, each group began to look more and more like its own ideal version.

This deliberate, artificial, selection was based strictly on external features, so it was those features that eventually defined the races.

There was no such process affecting internal features, so the "evolution" you are asking about simply didn't happen.


I hadn't realized that this process wasn't already well known.

The idea certainly wasn't original to me. (I remember seeing, just within the last year, a quotation from a scientist (ethnologist?) at the beginning of a TV program that expressed the same idea, but of course I don't remember what it was.)

I've searched for references for this process and can't find anything at the moment (I'll keep looking), other than something I wrote myself a few years ago:

Us versus Them

There is something in human nature that makes us want to identify with and to belong to groups of other human beings. We can see this grouping into "us" and "them" everywhere.

Children separate themselves into girls and boys; high-school students separate into cliques of jocks, nerds, and preppies; adults separate into Masons, or Rotarians, or Kiwanis; sports lovers separate into Mets fans or Yankees fans; and so on.

Two individuals can have extremely different backgrounds and interests, but if they meet as strangers and each is wearing a Yankees cap, they experience something that links them. There is no objective reason for this; unless they have bet money on the outcome of a game it really makes no difference to those individuals, much less the rest of the world, whether their team wins. But to them it is important; if the team wins they somehow feel that they personally have won, that they are personally better than they would have been had the team lost.

This phenomenon happens at all levels. Many people are proud of their city, their state, or their country for no reason other than that they are part of those groups. If you think about it, it really doesn't make sense, but it is a fundamental part of what most humans are. (If Texas really were objectively better than Oklahoma, everyone would abandon the one state and move to the other. Texans might say that the reason this doesn't happen is because all Oklahomans are too stupid to see the truth, thereby further illustrating the "us" versus "them" phenomenon.)

From a survival perspective, this attitude has had great benefits throughout history. If someone identifies more with you than with the person beside you, they are going to kill that person before they kill you. If you are in trouble, someone that identifies with you is much more likely to help you, even if only because they might hope the same of you someday. Having other people view the world in terms of "us" and "them" increases your chance of survival.


The earliest, most basic grouping was by family. We tend to look very much like our parents, our siblings, and our children, and we feel safest in their company. If we identify ourselves by that criterion, we will also have a slight tendency to identify with other people that look like us. We will naturally be more likely to work with, to be friends with, and to marry people that look like our family.

Isolated groups will develop an ideal image of what they look like, and over time members of that group will come to look more and more like that ideal. Children whose appearance is outside the norm will be picked on, and as adults they will be outcasts. These funny-looking or ugly people will be far less likely to survive or to find mates, and over generations the genes that make them look different will be eliminated from the community.

In a world of geographically isolated settlements, after dozens of generations, the inbreeding will greatly reduce each group's genetic variability. Each group will of course have its own unique selection of genes, different from that of all other groups. Where there is contact between groups, the "us" versus "them" nature will exaggerate those differences even more. It will be easy to see which members of the "us" community have "them" characteristics, and any such children will become outcasts.


Over the centuries, this "us" versus "them" inspired inbreeding is what has created what we now call race. Racism isn't the natural consequence of the existence of race. The causal relationship is actually the exact opposite. Race is the inevitable outcome of human nature's "us" versus "them" mentality.

  • Comments are not for extended discussion; this conversation has been moved to chat.
    – Carey Gregory
    Commented Feb 23, 2020 at 21:50

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