In biology, the concept of race is not recognized as being a real thing. This is because within any so-called "racial group," there are more phenotypic variations than there are across so-called "different racial groups." Seen in this light, the whole concept of race breaks down. And racism is a cultural phenomenon, not a biological one. There is no "racism gene." People do not inherit racism, they learn it.

@Flyingsaucesir scientists define "(phenotypic) natural selection" specifically as "those mechanisms that contribute to the selection of individuals that reproduce", without regard to whether the basis of the selection is heritable. [en.m.wikipedia.org]

Learned or not, choice of a partner to reproduce to pass on gene Pool to next generation is a part of natural selection.

@Word
Sexual selection is a type of natural selection, and mating preferences don't have to be heritable. (I never said they did.) They can be (and often are) culturally driven. All that is true.

I think you way over estimate the importance of racism in isolating sub-populations. In fact, racism is only a very weak barrier to mixing, even where there are miscegenation laws on the books prohibiting so-called "interracial marriage." Let's face it: when it comes to imaginary differences like race, love is blind.

I will repeat my main point: the human population is huge (nearly 8 billion individuals), and is considered ONE population precisely because no part of it is genetically isolated from any other part. Genes are flowing every which way, into and out of every sub-population, even where there are strong legal or cultural proscriptions against intermarriage. This is textbook biology, by the way. Not my opinion, but scientific fact.

@Flyingsaucesir I am 1/16th Cherokee with the majority being of European caucasians.

I think I could safely say, some of those of the tribes that has been here prior to the European invasion of 1492 may NOT contain any genetics of the European invadors since 1492. I am not saying racism is specifically keeping the genetics seperated, but I don't think the genetic are mixing quite like you are trying to say they mix.

Cynthia Ann Parker is example of how one race mergeges into another. I think it is more of the rare exception and can happen, but not the norm.

[en.m.wikipedia.org]

@Word
It does not take a lot of gene flow to de-isolate a sub-population. Basically, if there is ANY interbreeding between sub-populations, then they are NOT isolated.

@Flyingsaucesir bob and sue, are of same race and have 4 children. The 4 children each have 4 children of the same race. Bob and sue now have 16 grand children of the same race genetics. Each grand child has 4 children. One grand child of the 16 mixed with a different race. Bob and Sue now have 64 great grand children. 4 out of the 64 are mixed Are you saying the population of the ancestry of Bob and sue is totally "de-isolated"?

@Word
According to the 2010 Decennial Census, 0.9% of the U.S. population, or 2.9 million people, identified as American Indian or Alaska Native alone, while 1.7% of the U.S. population, or 5.2 million people, identified as American Indian or Alaska Native alone or in combination with another race.Jun 1, 2020
[ncai.org] › about-tribes

So you and about 2.3 million other Americans identify as mixed Native American/other. Now are you starting to see what I'm saying? No sub-population in the USA (or anywhere on Earth) is reproductively isolated.

Even if that core group of tribal folk keep exclusively to themselves, genes keep on leaking out into the wider community. That means neither is reproductively isolated. In terms of gene pools, they are one.

@Word
Yes. This tutorial in biology was brought to you free of charge. You're welcome!

@Flyingsaucesir so if all the 64 grand child(4 mixed) continue in the original race of Bob and sue: how are the 60 great grand children and their non-mixture genetics "de-isolated"?

@Flyingsaucesir those of the genetic mixture from Bob and sue move to California. While in California a massive Earth quake causes California to fall off the map into the ocean kill all the mixture of Bob and sue ancestry. How are the survivors that are not mixed still "de-isolated"?

@Flyingsaucesir I think, De-isolation may be relative to scale of viewing. On the over all scale of American continent there could be something called De-isolation or a mixture. Where as viewing smaller scales with in that over all group, I think there is still isolation of some genetic.

Not everyone in the American continent has mixed genetics. America has been called a melting pot. However, like a home made stew, chunks are still distinguishable. If you take the mixture of stew and put it in a blender, then what comes out of the blender has not identity of seperate chunks. It would be rather fully de-isolated on that scale.

@Word
The so-called "chunks" you are focusing on are miniscule and insignificant. Remember, the starting place is that we are all much more alike than we are different.

"All human beings are 99.9 percent identical in their genetic makeup."
[genome.gov] › Gen

The superficial differences between different ethnic groups are, for the most part, meaningless in terms of reproductive fitness. If they exist at all, they are far overshadowed by structural biases in society (I mean racial discrimination, and I think one could argue that even those are slowly going away...at long last).

You talk about different scales, but in evolutionary biology there us only one scale: the population. And the human population has 7.9 billion individuals, and they all have multiple transportation modes at their disposal. No part of the human population is isolated from the rest. It's all one.

Hey, don't take my word for it. Get yourself a good college textbook on biology. I'm sure you can find a decent, fairly up-to-date, and inexpensive used copy in your local university bookstore.

@Word
You say, "Not everyone in the American continent has mixed genetics."

Oh yes they do! Even if they are "100% European."

There is no such thing as a "pure blood" human being. The mixing has been going on for a very, very, very, VERY long time.

I am reminded of the case of the white supremacist (he was very proud of his Aryan heritage) who agreed to have his DNA analyzed, and, much to his consternation, found that he was 17% sub-Saharan African.

@Flyingsaucesir Not everyone in the American continent has mixed genetics."

Again my point as to "scale". I understand, neanderthal and and Denisovan genes are mixed in with what is now homo sapian. So, pure blood as you imply is not my point.

I have had high school and college general biology with 4.0 gpa. It's been years, not specifically my forte but I have introductory general understanding. Sure, some perhaps more advanced information I may not be educated on.

Another example of my point. My mother is 100% European caucasian, my father 1/8th Cherokee. You say my mother is in "de-isolated" America. If my mother returns to Europe and has a child there, does she take her American "de-isolation" with her even though she has no native American Gene's? Where as If I go to Europe and have child with a European I am bringing different genetics with me.

@Flyingsaucesir take the stew, chunks of potato, onion, celery, carrots. American de-isolated you say. Take one bowl and set aside. Place half in blender and take the other half to Australia.

After blending thoroughly the one half, remove only one chunk of potato from bowl set aside.

You have an isolated chunk of potato in a blended 'de-isolated " mixed up American stew and how does it all compare to Australian flavor of stew with kangaroo rather than beef?

@Flyingsaucesir there is isolation and re-mixture.

The shifting nature of these habitable zones means that human populations would have gone through many cycles of isolation—leading to local adaptation and the development of unique material culture and biological makeup—followed by genetic and cultural mixing.
[phys.org]

@Word
I will bring you back to the original question: have humans stopped evolving?

Probably.

With a gene pool as large as ours, and with all the opportunities for transportation that are available, and with our animal desires, there is (and always has been) a lot if mixing. Just consider for a minute all the sailors with a woman (or several women, many having migrated from other places themselves) in every port. Sure, there can be some evolution in sub-populations. But they do not remain isolated long enough to become different species. Instead, their gene pools become diluted, and any new genes they contribute to the wider population become lost in the mix, less than a fraction of a drop in the bucket.

Your hypothetical scenarios really do not elucidate the problem. For every scenario you can come up with there are ten thousand that cancel it out.

That's very nice that you have taken general biology. You should be well equipped to refresh or update your knowledge with a college textbook.

@Flyingsaucesir You say," I will bring you back to the original question: have humans stopped evolving?

Probably.. "

Although de novo genes remain enigmatic, their existence makes one thing clear: evolution can readily make something from nothing. “One of the beauties of working with de novo genes,” says Casola, “is that it shows how dynamic genomes are.”

So, humans could still evolve by way of "de novo genes"?

I say probably still evolving in consideration of the following.

Counting de novo genes in the human genome comes with the same trail of caveats. But where de novo genes have been identified, researchers are beginning to explore their roles in health and disease. Zhang and his colleagues have found that one gene unique to humans is expressed at a greater level in the brains of people with Alzheimer’s disease14, and previous work15 had linked certain variants of the gene to nicotine dependence. For Zhang, research that links de novo genes to the human brain is tantalizing. “We know that what makes us human is our brains,” he says, “so there must be some genetic kit to push the evolution of our brain.” That suggests an avenue for future studies. Zhang suggests that researchers could investigate the genetic kit through experiments with human organoids — cultured cells that serve as a model organ. [nature.com]

I'll just address one of those three "examples." Take temperature. If there really is a cooling trend, it may be (and probably is) a response to conditions that is well within the scope of our present genetic makeup. In other words, place people in conditions like those of 150 years ago and they would respond as people did 150 years ago. It's similar to what is going on with human body size. In North America and Europe, people used to be smaller, on average, than they are today. That's because our nutrition is better today. Go back to the diet of 1850 America and people would not get as big as they do today. All we did in getting bigger with a better diet was realize a potential that was there all along. It was not evolution.

True dat.

Evolution is in the realm of science. And I'm giving you discussion based on science. The facts are that the human population is huge and no part of it is genetically isolated from any other part. These two factors, large population and no reproductive isolation, place a huge brake on evolution. Remember, evolution occurs at the population level. Genes do not evolve. Individuals do not evolve. Species do not evolve (unless they are limited to only one population). Only populations evolve. This is textbook biology, not my opinion, wish, desire, decree, or caprice.

Ah, you miss the point my friend. Biologically speaking, there is only one human population. I know it it is tempting to view every country, or city, or region as having its own separate population, but in terms of evolutionary biology, they are all really just one.

I am aware of that. I did not make that mistake in my response.

Really? Where is your evidence?

@Flyingsaucesir All living organisms over time.

@wordywalt
There is evidence of evolution within sub-populations, for example the decrease in the frequency of the sickle cell allele among African Americans. But that does not really count; it's only a small fraction of the world population. When we talk about human present-day evolution, we have to consider the whole population. All 7.9 billion of us.

Even the sickle cell example is questionable. The decrease in allele frequency among African Americans could be due to dilution of that sub- gene pool. Rape of black slave women by their white masters was common practice for hundreds of years. And interracial marriage has always been a thing, even where there were miscegenation laws on the books. More study is required.