Okay question for everybody.
How do we define a nation or ethnic group?
Food and flag colors?
Skin color?
Religion?
Is there some sort of mystical “national soul” or can it be measured empirically?
Ethnicity is a group of people that identify with each other based on the basis of a shared culture, history, language, and generally bloodlines. They also generally share a similar and local geography.
So the natural question is, which is the defining factor or factors?
But before we can do that, we need to look at what a nation or a ethnic group actually is; it is a super organism. A super organism is an organism that is made up of various individual organism that acts as a single entity. This is most obvious in species like ants and termites, who are also super organisms. This is why when anyone, down to a child, studies an ant colony, they can notice strong commonalities between human society and ants.
Now, with an ant colony, who is and is not part of the tribe is generally dependent upon genetics and smell. If you don't come from the queen ant's line (ignoring male ants) then you are generally seen as a competitor and it's war. An interesting look though, is at the super ant colony of Argentine ants that now expands worldwide.
Argentine ants have various Queens in their colonies, which allows for higher reproduction rates and their colonies tend to span a much larger range than most other ant nests. Another interesting note is that the ants themselves are so genetically identical to each other that ants can go from one nest to a neighboring nest and not be attacked--they are in fact, accepted as one of them. This gives them a competitive advantage over the ants of other parts of the world, because those ants make smaller nests and are more genetically diverse. Only members of different super colonies appear to have some adverse reaction to the other, from simply avoiding each other to outright killing each other.
Now, within Argentina itself, these ant colonies are not so massive as they are elsewhere. Because the genetic differences have already set in within other Argentina ants and so despite these species of ants having larger nests than other ants, they still fight with each other as is more common with different ant nests. Eventually though, even these super colonies may collapse as stretching over such large areas, these super colonies will each begin to adapt in different ways and that adaption itself will produce genetic differences that will cause these super colonies to collapse.
In fact, the University of California is working on spraying these ants with a special chemical that is similar to the ones they use to determine colony affiliation, so as to collapse these super colonies by forcing diversity into their social structure.
So what does this have to do with humans and ethnicity?
It's simple. Just as ants, humans are a super organism. Just like ants, we have traditionally associated ourselves with our near genetic groups. Unlike ants, we use to determine this association not with smells, but rather based on physical appearance, language, cultural norms, and historical knowledge passed down from parent to child (as a side note, ants have been tested and shown that they remember things long after the initial ants die; they create scent trails and patterns around their nests that although each individual ant does not remember having done, the super organism itself remembers, which has been compared to the human mind, in which individual cells die, but the knowledge is retained).
Also unlike ants, we do not all come from the same female mother and lack general competition within our own super organism. Instead, our male to female ratio is closer to 50/50, with men and women competing against those within their own gender for the best mate, which takes into various complicated information such as established genetics, ability, health, wealth, and social status within that super organism. What that means is that when you compare ants and humans, ants within the same colony are almost genetically identical compared to humans.
This is from basic math. If you have one queen that produces all the workers from being impregnated by the male ants, then you have a very uniform genetic history with a hundred ants. If however, you have a hundred humans, you have 50 pairs of people mixing their blood. More onto that is that those humans can and will mingle with other humans from different tribes that they find to be attractive. This induces a great deal more genetic, social, and linguistic distinctions than what would otherwise exist if we were more like ants.
And that brings us to the answer in your question. What makes up an ethnicity is the belief of a shared group association. It is within the nature of all things to mutate and change. The Argentine ant super colonies will become genetically diverse to adapt to their local geographies. And in doing so, they will "forget" their ethnic identification with their mother colony. Just as humans can forget through time and distance to be related to each other.
Take African Americans within the United States, for example. Most African Americans are actually 24% European. But they do not associate themselves as 'white' for various factors. The first is that mixed children within the Deep South were always considered to be black, not mixed, as was part of the caste system. Thus, the vast majority of these African Americans never held the social memory of having been 'white'. Therefore, they associate themselves with the black nation. More and more now however, you see men and women of mixed relations thinking of themselves as mixed and less as 'black'. This trend will likely continue.
And if you look at Hispanic people within the US, you find that they are on average 65% European and only about 18% Native. And yet they're treated within the US as a completely different race. The reason is of course that they are Spanish and have had centuries to build up a different culture than we have.
What will happen is this; African Americans will probably see a blurring effect as people slowly began to disassociate them from being black to being mixed to being American with African and European heritage, as Europeans themselves were eventually merged and saw themselves first as Americans, then second as of holding a different heritage. The Hispanic population will be slower and the closer they are to Mexico the less likely this effect will take place, but they till will be absorbed. However, because of Mexico's proximity to the US, there is a means of maintaining a separate identity to the US.
This will happen because the US itself is a very fluid system of mobility within its geography. Getting to the US continent is hard, but once you have a foothold, the geography actually encourages inter-connectivity. That's not to say there aren't and can't be conflicts, but they are lower than in places like Europe and within the US, the common identity shared as being one whole group is most advantageous and will probably continue into the foreseen future.
