Okay, so I had this idea that there is a group of refugees (a majority of them civilian families) taking cover from an invading force, vanishing into a mountainous region that serves as a natural fortress to protect them. These refugees are fairly ethnically diverse in the beginning, and number between 2,000-2,500. Assume level of technology to be bronze age, or thereabouts. Surviving in the mountains will be tough, and I assume that they will lose people to injury, illness, and exposure, especially in the beginning when their surroundings are unfamiliar to them. It also isn't realistic that they would be completely isolated, so assume that there are marriages with outsiders occasionally, even if that is culturally frowned upon and ends up being rare- perhaps one every few generations?

Keeping all of that in mind, how long would it take said population to develop fully into their own ethnicity, both in appearance and in genetics?

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    $\begingroup$ Ethnicity is a cultural phenomenon, and has precisely nothing to with physical appearance. There are blond Germans / French / Italians / Romanians, there are chestnut-haired Germans / French / Italians / Romanians, and there are brunette Germans / French / Italians / Romanians. There are Afghans with brown eyes, there are Afghans with blue eyes. (And we know that this also held for ancient peoples: some Greeks and Romans had dark hair, some had blond hair, some had red hair.) (P.S. As a cultural phenomenon, ethnicity is very plastic -- one to three generations will easily be enough.) $\endgroup$ – AlexP May 11 at 22:03
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    $\begingroup$ @AlexP Ethnicity can mean multiple things. The word is also in use as a less offensive-sounding word for race; or phenotype. Someone's general appearance as determined by their genetics. Yes there are blonde Italians but we can say that a native Italian is statistically less likely to be blonde, and that is because the genetic makeup of the average Italian differs from that of the average German. $\endgroup$ – KeizerHarm May 12 at 0:04
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    $\begingroup$ @KeizerHarm: The "average Italian" is an average of Italians with Italic (= Latin/Sabine/Sabellic etc.) ancestry, Italians with Celtic ancestry (northern Italy was Celtic country back in the day), Italians with Etruscan ancestry (that's why Toscana is called Toscana), Italians with Germanic ancestry (that's why Lombardy is called Lombardy), Italians with Greek ancestry, and Italians with Arabic / Berber ancestry. And this is only for "autochthonous" Italians, disregarding modern admixture. Similarily, the "average German" may have Celtic, or Germanic, or (for half the country) Slavic ancestry. $\endgroup$ – AlexP May 12 at 0:21
  • $\begingroup$ @KeizerHarm: The point is that the biological make-up of European populations has been surprisingly stable since the Antiquity. The ethnicities of Europe, very much not so. The boundaries of ethnicities and the boundaries of genetic variation rarely match. $\endgroup$ – AlexP May 12 at 0:23
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    $\begingroup$ @AlexP To some people, every Asian person from Ulaanbaatar to Saigon looks the same. I would personally not make the comment that you just made about the residents of Slavic countries. $\endgroup$ – KeizerHarm May 12 at 0:41

Ethnicity is an Idea first, Biology a distant second:

There is a similar question HERE

The problem with race and ethnicity is that the divisions are largely cosmetic. That is to say, all you need is for your group to LOOK different from the surrounding people, and they are considered different. If you have a distinctive feature, like red hair or a funny nose, then as soon as that trait is prevalent in the society, it's an ethnicity. The line between culture and ethnicity is a fuzzy one, and I'd argue that in practical ways, it's an illusion. There isn't an absolute scientific rule saying what an ethnic group IS or ISN'T. And ethnicity is a murkier thing even than race, which is in-and-of-itself a controversial topic.

Uyghurs, for example, are considered racially Central Asian (if you want to make the distinction), but based on language and religious differences, they are considered their own ethnic group. The Chinese government certainly considers them different, and the efforts to eliminate their culture are labeled genocide.

But it can take even less time if you have something in the environment that imposes conditions on people to change their appearance. Say one group has abundant meat, and their children grow taller than their neighbors. With cultural differences and language drift, they could be an ethnicity in one generation. Do you consider (European) Australians to be an ethnic group or a nationality? If so, then it took maybe 150 years (or less).

So your group isolates, then their weaver develops a particular clothing style based on local materials. They have lots of garlic, and so all their food has garlic because there are almost no seasonings to be had (spices were huge in the ancient world). Ted the blacksmith likes to say "belike" in a funny way, and everyone likes Ted, so pretty soon the folks sound a little like Ted and it becomes more pronounced when Ted becomes mayor. His wife was from France and French words creep into the vernacular. Ted likes to bathe every day, and learning how to make lye soap becomes a priority as habits establish themselves. The one preacher in town has his own ideas about God, and his teaching is a bit off from the surrounding communities, but everyone goes with it.

So now people settling new areas but coming from your village dress differently, talk differently, eat differently, worship differently and possibly SMELL differently (garlic can be strong, and soap important). They may have fewer skin problems because of good hygiene, and Ted was a good mayor, so the kids are tall. King Ted the second keeps the community together even as it spreads. Now they track government differently.

So I'd argue that within a single generation, you have AT LEAST a unique culture, and will likely be considered a unique ethnicity. As Ted's big nose spreads through the population, the Tediites will be an ethnic group within perhaps three generations. Large numbers of other peoples in close contact will blur these lines, but that's because ethnicity is in the eye of the beholder.

  • $\begingroup$ The phrase "racially Chinese" is meaningless -- China is a large empire with many and varied sorts of people. If you mean "Han", then no, they don't look like Han people, they look like Central Asian people, indistinguishable from their neighbours and close relatives the Kazakhs; which is not surprising, given that they are Central Asians. If you mean "slanted eyes" then, well, duh, that's lots and lots of peoples. $\endgroup$ – AlexP May 11 at 22:06
  • $\begingroup$ @AlexP I agree, most distinctions based on race and ethnicity are pointless, meaningless, and shallow. I can change the wording, though, to be more precise. $\endgroup$ – DWKraus May 11 at 22:14
  • $\begingroup$ @AlexP: But in the case of the Uyghurs, "ethnic" is really a codeword for religion. Rather like the Catholic/Protestant divide in Ireland: no one - certainly no outsider - is going to be able to tell the difference between them on physiology. $\endgroup$ – jamesqf May 12 at 17:13

I upvoted @DWKraus' answer, you should too, but I want to add more insight.

Answer: 30 Seconds

eth·nic·i·ty (/eTHˈnisədē/) noun: ethnicity; plural noun: ethnicities • The fact or state of belonging to a social group that has a common national or cultural tradition. (Source: Oxford Languages)

Your group of refugees met that definition the moment they became refugees, sharing a common enemy, a common plight, and the common goal of survival.

If, on the other hand, what you meant was, "if a community of some 2,500 people begin with a variety of ethnic backgrounds but became isolated, how long would those backgrounds merge into a reasonably homogeneous single ethnicity?"

Answer: Basically never

One of my go-to examples of the complexities of ethnicity is the historical background to the Bosnian Genocide. From 1918-1992, Serbia, Croatia, Bosnia, Montenegro, Slovenia, and Macedonia were better known as Yugoslavia (My thanks to @AlexP for correcting me!). For nearly seventy-five years four generations of people lived in first the kingdom and then the socialist state. They worked together, played together, intermarried between ethnicities, fought together... And then came ethnic independence. And then came war. And then came genocide.

What the world learned from that experience (among many other things) is that hate can be quietly and effectively handed down generation-to-generation no matter how closely people are brought together.

From a very real perspective, you need more than 75 years to merge peoples into a single ethnicity.

We can look at nations all over the world showing better-than-average conformance and worse-than-average conformance. Let's take France for example. The Greeks, Gauls, Romans, Germans, English... they all fought and mingled until today where you have a remarkably tight culturally bonded people. I've known some French people — they're amazing! And when you get their nationalistic and, perhaps more importantly, cultural backs against the proverbial wall, there's being French... and there's everybody else.

Compare that to the U.S. where we have ethnic divergence all over the place, often at odds one with another. Skin color. Dialect. Heritage. A 250 year melting pot that has not in any way created a single ethnicity and probably never will.

Whether or not your people will create a unique ethnic heritage depends on some very powerful factors.

  • What heritage did they come from? Was that heritage traditionally submissive or arrogant? Was it traditionally inclusive and tolerant or xenophobic? Was it a big deal to be a member of that ethnicity, or was it just something you were and being a member of a political party was more important? Etc.

  • What animosities exist between the initial ethnic representations? Remember, hate can and will last a honking long time. Remember Newton's First Law? Hate is one of those powerful forces, and it will remain in motion until acted upon by an equal or greater force. Yeah... think about that. When the Beatles sang "All You Need is Love," they were very right... and very, very wrong. If you don't believe me, wait until one of your children turns 13 (All you need is love! La-ta-da-da-daaa!) As a friend once said, "I finally understand why lions eat their young...."

  • What conflicting social/cultural rites exist among your group? Does one have a religious practice that another finds heinous? Let's through polygamy into the mix and let one of the polygamists' sons start dating your daughter.

  • Are there physiological differences between the ethnic groups? Skin color? Eye shape? Nose size? Height?....

As you can see, your group will take as long or as little time as you desire to develop an ethnicity. You can create all the initial starting conditions to justify the time you want it to take. Thirty seconds or a thousand years. It's really up to you. There is no single right answer.

'Cause at the end of the day, long as there's two people left on the planet, someone is gonna want someone dead. (TF2, The Sniper)

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    $\begingroup$ "Bosnia and Herzegovina were better known as Yugoslavia": Bosnia-and-Herzegovina is one of the parts which made up ex-Yu. The mnemonic is "two alphabets, three languages, and six republics". The alphabets are Latinitsa and Cyrillitsa. The languages were Serbo-Croatian (spoken is Serbia, Croatia, Montenegro and Bosnia, each of which of course today says that it has its own language, strangely fully intelligible with the others), Slovene, and Macedonian (the same as Bulgarian, but don't tell that to a Macedonian). The republics were Serbia, Croatia, Bosnia, Montenegro, Slovenia, and Macedonia. $\endgroup$ – AlexP May 12 at 0:39
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    $\begingroup$ The United States is an extremely poor example. The only thing preventing a monoculture is the influx of new immigrants which keeps their previous cultural influences. In the distant past American Immigrants were primarily European. Those Europeans became the monocultured "White Americans" with a handful of holdout communities which kept their cultural roots. The same happens with 2nd and 3rd generation immigrants. They largely become American. Imagine a melting pot you never stop adding ingredients to. The new ingredients always need time to melt and merge with the whole. $\endgroup$ – Hippeus_Lancer May 12 at 1:27
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    $\begingroup$ @Hippeus_Lancer I see your point, but I don't think that the New England culture, Motown culture, Texas cultures, Native cultures, etc. are all prohibited from merging simply because of new blood. I used the US as an example of a region that would take forever and a day to coalesce and if/when it does, it will be very loose (IMO) vs. a nation that coalesced very strongly. Just pointing out the problem of asserting there's one right answer to the question. $\endgroup$ – JBH May 12 at 1:55
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    $\begingroup$ @Hippeus_Lancer: Exactly. For example, where I grew up (in the northeast US), there were a number of people with Spanish surnames like Garcia, Diaz, and so on. But their ancestors had mostly been in the area since Colonial times, they intermarried with everyone else in the area, so the only remnant of Hispanic-ness were those names. $\endgroup$ – jamesqf May 12 at 17:20
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    $\begingroup$ "The only thing preventing a monoculture is the influx of new immigrants which keeps their previous cultural influences." Many African-Americans would disagree - and they've been living in America as long as many European-descended Americans have. $\endgroup$ – nick012000 May 13 at 4:25

In truth modern science cannot not really answer this. Actually, it probably could, but… because of issues that are grounded in politics, racial debates, and the fears of indigenous people in the Americas (North & South), science has not been able to make its best attempt at solving the wide spread, and very hotly debated question that you ask. Remains from a group of people known as the Clovis people have been found all over the American continents, as far as I know, more commonly in the Northern continent, than the south, however; the Southern continent, and Mexico (which is technically part of the North, but perhaps a more accurate description, one that is often used to reference the Mexican Region, would be Central America) has produced much much older anthropological finds, including artifacts and human remains from periods that predate the latest known period that the Clovis people lived in the Americas. If you read this article, you can get a good idea of the arguments raised in this subject. The whole point to mentioning the topics that I did above, is to raise the question where did Native Americans come from, who were their ancestors? There is a wealth of data on this topic now that could help us answer these questions, but the “should be easy to collect data, has not been so easy to collect”. To tell what remains belonged to persons that were related, ancestrally, to the Native American Tribes people we must test the DNA of the remains, then test the DNA of modern Native Americans. Any attempt at doing this pisses someone off. Many tribes will not give consent to not only sample their DNA, but they have had legislation passed that prevents DNA testing of their ungraved ancestors, or of any peoples predating contemporary European settlement. In-fact many of the remains we have found, have had to be study rather quickly as legislation has forced scientist to rebury one of a kind precious remains. With that said, there has been some work done, with some useful data, but the conclusions produced from the data are arbitrary, and more data is needed to reinforce the claims made by Archeologists, and Anthropologists.

Link that demonstrates arguments about this subject

There is pretty good evidence that the Clovis people are very distant relatives of many of the Native American Tribes people, but what is hotly contested is the remains found that predate the Clovis people, DNA shows some similarities, but as stated previously, all DNA work that could be done, has not been done, and several chances to do DNA testing have slid right by us, and are no longer available due to the re-graving of remains that were never DNA tested when they were ungraved. Currently it is theorized by some scientist, and this is becoming more widely accepted with the passing of each day, and not a lot of new data coming forth, several American Tribes are descendants of the Clovis people, this is easy to accept because DNA evidence suggests it. The group of people that predate the Clovis people show DNA similarities with the Clovis people, but they don’t show much evidence as being related to the North American Tribes, however, the key word is Much, there is little evidence, but not nearly enough to conclude concretely. Furthermore, upon the topic of scientific theory, it is hypothesized that the data shows exactly what you would expect to see when a new ethnic group is established. The latest ancestors don’t show a lot of DNA resemblance, but more recent ancestors show damning evidence that they are related to the new ethnic group, therefore; it is very likely that the reason we see less and less Native American resemblance as remains grown in age is simply because the remains grow less related with age, this is in fact how it works.

It's not as simple as I made it sound when I concluded the last paragraph, but I believe that what I have said, and so do many others, that what I have stated above is at-least partially true. It would be hard to say that it would take a specific number of years to form a new ethnic group, but when coming to a conclusion based solely on the data that is available, it looks like 24,000 years or more.

  • $\begingroup$ I just answered this question on Quora as well $\endgroup$ – JayDev May 12 at 3:13
  • $\begingroup$ Six generations is no where near the amount of generations it would take to establish a new ethnic group, a new culture maybe, but not an ethnic group. For an ethnic group to be an ethnic group, that ethnic group needs some uniqueness in the DNAs Haplo-groups. $\endgroup$ – JayDev May 12 at 3:23
  • $\begingroup$ I am no biologist but I would expect that it would require enough time, and generations to create a new DNA group similar to the human mitochondrial DNA haplo-group. $\endgroup$ – JayDev May 12 at 3:24
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    $\begingroup$ @AlexP To be fair, genetics can say that certain genetic markers are more or less frequent in certain populations, and if a person has a high prevalence of markers found within a given studied group, they can say with modest certainty what ethnic group a person is most likely a member of. But genetic markers are more indicators of relation, not causation. Sickle cell anemia is a trait, not a defining characteristic. I love this example for it's messy complexity en.wikipedia.org/wiki/Lemba_people $\endgroup$ – DWKraus May 12 at 12:22
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    $\begingroup$ @AlexP The definition of Ethnic group is vague, and furthermore, what any particular ethnic means is contemporaneity debated subject. What is not commonly debated, because most sane people accept it as science, is whether or not ethnicity can be tracked by DNA. Each of the groups that you claim cannot be defined by Human Y Chromosome DNA Haplo Groups (which basically means DNA obtained from mothers) ...is in fact defined by them, and unlike you I will cite my claim. Here is actual science that shows DNA can define ethnicity en.wikipedia.org/wiki/Y-DNA_haplogroups_by_ethnic_group $\endgroup$ – JayDev May 13 at 8:24

I don't think there is a 100% clear cutoff line, because ethnicity is much more of a social distinction than a physical one. Is Anglo-saxon a different ethnicity from white european? Is Scottish an ethnicity separate from anglo-saxon? Is lowland scottish separate from highland scottish? Are American Scots a separate ethnicity from Scots living in Scotland? Are American scots a separate ethnicity from Canadian scots? Is Scots-Irish its own ethnic group separate from Scottish and Irish? What about American Scots-Irish vs Canadian Scots-Irish? What about Canadian Scots in Nova Scotia vs Canadian Scots in Ontario? Which of those count as separate "ethnicities", and why?

What if an Ulster Scot immmigrant to Indonesia who identifies as Scots-Irish has a kid with someone who is Han Chinese but speaks Bahasa Indonesia and identifies as Chinese-Indonesian -- are they ethnically distinct from someone who differs from that only in that their second parent is Hui-Chinese instead of Han-Chinese?

If you have a village with two predominant family lineages, one of which has greater percentage of blue eyes, and the other which has greater percentage of green eyes, are they considered ethnically different in appearance from each other? What if their larger culture thinks they are ethnically different? What if their larger culture thinks they are ethnically the same, but they themselves think they are ethnically different?

There are a million other grey areas. Willk is probably right that 6 generations is a decent estimate assuming a genetic mutation occurs in the first generation that directly translates to a clearly distinguishable change in appearance, with perfect conditions and everybody marrying each other completely randomly (would this really be the case?). However, I would argue that the minimum for being treated as a separate ethnicity would be 0 generations. Simply living somewhere else could be grounds for some cultures to believe they are ethnically different. Even differences in food, nutrition, fashion, living conditions, etc. could be enough to cement a commonly-agreed-upon ethnic division. Human history is full of stories of people drawing arbitrary lines between each other and declaring their own tribe's uniqueness over the others.

  • $\begingroup$ We see in every generation a new "ethnicity" happening with our teenagers. They talk a different language and engage in different customs. $\endgroup$ – David R May 11 at 22:59

They would not regard themselves as an ethnic group. They would regard themselves as basically, a group, and those outside are the outsiders. For instance, in 19th century France, villagers would refer to a bride who came from outside -- meaning another village.

This group comes with a natural regard for themselves as a group, since they can easily distinguish themselves from the invaders or the cowards who submitted to their rule. The necessity to work together would reinforce this.

In time, their language and culture would diverge, and their intermarriage will homogenize their genetics. (Especially culture, since they now face the necessity of doing things differently in the mountains.) However, they would not regard this as a difference between themselves and their ancestors. They are still those who fled to the mountains to avoid submission to the invaders. "Ethnic group" is something this would be termed by outsiders.


There are plenty of good answers already, so I will just provide some additional information on the subject. It is not possible to give you a reliable estimate because the speed of cultural homogenization depends on several different factors. Some of the most important are:

  1. Diversity of the original group (do you have dominant ethnic or cultural subgroups? what are their relationships with other subgroups?)

  2. Patterns of marriage and settlement (do people from different subgroups intermarry? do subgroups live in their own 'ethnic' villages?)

  3. Religions (are there big differences in religious views and traditions? how strictly religions are observed? can people of different denominations intermarry?)

  4. Governing and policies promoted by the leadership (do leaders promote intermixing and intermarriage? do leaders allow 'ethnic' villages? do leaders strive to achieve cultural homogeneity?)

  5. Environment (can the group split into subgroups without endangering itself? what kind of activities are required to sustain the group? how much cooperation is required for survival?)

With an initial population of 2000, it is possible to end up with 2-3 ethnic groups if the original group had 2-3 big factions that differed in culture, language, and religion, cooperation was not very important, people quickly settled down in small 'ethnic' villages and did not intermarry.

On the other hand, if people had to live close to each other, had to work together, intermarried quickly, and did not have major religious disagreements cultural homogenization would happen rather quickly - within 2-3 generations.


Let us assume "ethnic group" means they can be distinguished as that group on sight. Let us start with something harmless and spectacular like the methemoglobinema of the Blue Fugates.

blue fugates


Let us assume that the gene conferring the appearance is autosomal dominant like Huntingtons, so instead of needing a double recessive like the Blue Fugates you have a 50% chance of manifesting the phenotype if you have an affected parent.

Let us assume further that there is a fitness benefit to this appearance such that for whatever reason more children with the gene will live to have their own children.

We will assume a stable population of 1000. In this population, every child with the gene grows up and is part of the next generation. Other children might or might not.

There is 1 founder among the refugees. In the second generation the founder has 5 children. Each of these children have 5 children, so 25 with the gene in 3d generation, 125 in the 4th, 625 in the 5th and by the 6th generation the entirety of the 1000 person population carries the gene which confers this group their appearance.

Of course there is more to "ethnic group" than skin color. I am sure though after 6 generations this isolated group would certainly have their own customs and would likely speak in a dialect hard for outsiders to understand.

  • $\begingroup$ You could theoretically speed this up even faster if the gene is linked to a trait that affects adult survival rather than just reproductive success. E.g., a gene that causes...say...purple eyes being genetically linked to a local variant of a gene that protects against a mosquito-borne illness. Wild-type individuals will disappear very quickly in that case. $\endgroup$ – user2352714 May 11 at 21:32
  • $\begingroup$ "Harmless" is questionable, because of the susceptibility to linked blood disorders, but definitely spectacular. $\endgroup$ – jdunlop May 11 at 21:58
  • $\begingroup$ One cannot distinguish between ethnic groups on sight. Please tell me how can you can tell if a person is German, Dutch, or Danish just by looking at them; or for an even clearer example, how do you distinguish between a Serb, a Croat and a Bosniak by looking at them? And those people fought a savage war in the 1990s exactly along ethnic distinction lines. (Ethnic groups are very much finer grained than the broad differences between geographical populations, and their boundaries do not coincide.) $\endgroup$ – AlexP May 11 at 22:19
  • $\begingroup$ @AlexP It's funny, I know a Serb, a Croat, and a Bosniak (Bosnian?), and your comment made me picturing the three of them walking into a bar (but I suspect they'd all prefer Turkish coffee...) $\endgroup$ – DWKraus May 11 at 23:21
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    $\begingroup$ @DWKraus: A Bosnian is a citizen of Bosnia. A citizen of Bosnia can be a Croat (= Catholic Serb), a Serb (= Orthodox Croat), or a Bosniak (= Muslim Serbo-Croat). Ex-Yugoslav ethnicities are complicated. $\endgroup$ – AlexP May 11 at 23:25

how long would it take said population to develop fully into their own ethnicity, both in appearance and in genetics?

Somewhere around a few thousand years to ten thousand years.

  1. If you simply pick any Old World population 10k years ago and keep it isolated, you're almost guaranteed to end up with distinctive one by nowadays standard. Why? Because nowadays we're quite mixed, for example for Europeans are mixture of three such population. Any of those ancestral groups (Western Hunter-Gatherer, Anatolian Farmers, Yamnaya) would right now look somewhat distinct, especially WHG.
  2. Upper bound - out of Africa split has happened 70k years ago. So that would be the time that's guaranteed to work.
  3. If you need it to be really fast - then you have founder effect with very small starting population with odd gene variants and genetic drift. (ex. they had a few red haired people at start and by purely random event they become the dominant allele in a few generations) Also pay attention to local climate - if it's totally different than original one, then it would force quite fast evolution. (think: Inuit)

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