I’ve been thinking about it recently and concluded I don’t understand a few things about the common theory of human distribution many (many) years ago. The basic story being that having developed in Africa, the species went north, up into Europe, and east along the Asian continent. Then south to Australia and further east into the Americas as the geography at the time allowed land crossings. Is that right?
So what I don’t get is how people stayed still long enough to develop the differences we have between races. Indians all stayed in India. The Japanese all just sat on their island and went nowhere. The Koreans sat on their bit and went nowhere. And so on. This seems contrary to human tendencies for exploration.
How long is it supposed (or guessed) it takes to develop the features that give us difference races (i.e. skin tone, facial features etc)? Ten thousand years? Fifty? More? Less?
Why would EVERYone have just been sitting still and not exploring or traveling and mixing? I can understand the populations cut off by geographic changes effectively being stranded, but the rest…?
Are there other theories that would explain it better? Am I missing something?
Modern humans have a tendency to explore. Ancient humans probably only explored when population pressures demanded it. You don’t have time to do things like exploring when you live a subsistence lifestyle.
Actually, we seem to have made a bee-line to Australia before we went into Europe and north in Asia, but otherwise your timeline is roughly correct.
People were probably interbreeding along geographic lines continuously, but the population density for h/gs is very small, so it wouldn’t be as much of a factor as it is today, in a higher population density. Evolution doesn’t tick along at a regular pace, and depends on the environment, so there isn’t any set time it takes to develop what we’d call “racial features”. This is especially true of smaller populations-- that is, larger populations are going to be more stable. I have read that biologists think it took about 10k years for the mutation for white skin to take hold, but that’s just one data point.
Additionally, we don’t really know what set of genes the people who left Africa to colonize the rest of the world had and how much they may or may not have looked like modern Africans (who vary quite a bit, phenotypically, btw).
I think this is a little misleading on both scores.
Most modern humans do not explore. Technology makes us much more mobile, and yet most people still end up living around the same places as their ancestors.
But there is evidence that virtually all populations, throughout time, have produced explorer-type individuals. (I think this was discussed some in the National Geographic anniversary issue a few months ago.) These were the people that established new populations in areas not yet settled.
Once established, not everybody then sat still. There were new generations of explorers, traders, warriors, and migrants. But if most people are, most of the time, content to not be any of these things, and if adjacent territories are now mostly already occupied, then whatever cross-boundary genetic mixing occurs tends to wash into the larger pool of the less-intrepid stable populations. It takes a cataclysmic event to really change or dislodge the majority of any settled group.
More or less, I think, but see what John Mace says about Australia. (It seems odd, but that is apparently the current wisdom.)
Why do you think they would have to stay still to do that? Provided they didn’t interbreed too much with other groups, groups of people could be on the move and still evolving differences. (As social animals, humans do tend to join together in groups, and to migrate together when they migrate.) Remember, there just were not very many people in the world at all at that time. A group, even one spread quite thinly across the countryside, and on the move, might go a long time without encountering any other humans from different groups.
Again, why do you think that? There could have been plenty of coming and going in and out of India, Korea, Japan etc. over the course of time.
I guess because Indians and Koreans appear pretty dissimilar. But I suppose they could’ve been traveling and mingling with each other but not having sex… again, seems contrary to human nature and male tendency to stick his dick any place it fits?
Perhaps the smaller population at the time is the main factor.
The first (or some of the first) modern humans to leave Africa seem to have moved eastward along the tropical coasts of southern Asia. It makes sense for the first colonists to have stuck to the kind of warm climates they were used to in Africa before colonizing the cooler parts of Eurasia. This first colonists seem to have left traces behind in populations with “Australoid” type features, like certain isolated tribes in India, the Andaman Islands, and the various Negrito groups of southeast Asia and the Phillipines. Similar peoples eventually reached New Guinea and Australia.
I don’t think people changed much between now and then. I think the issue is you haven’t recognized why modern peoples don’t seem to migrate as much.
It’s because, no matter where you want to migrate,* there’s already someone living there.* What prevents population movements isn’t some innate lethargy, but armed people determined to hold the ground you’d like to migrate to.
When we came out of Africa there was literally no one else human in the world, and we radiated into all the available niches, like any other species.
For a long time after that, population densities were low, and you’d still see vast migrations of humans, like the Indo-European language groups imply.
Once everywhere was filled up with people, however, war was the only way to displace determined neighbors, and peoples tended to be more stable in the regions they then occupied.
That is true only for very restrictive values of “human”. There were certainly populations of the genus Homo outside of Africa when the modern version of our species first left the continent. Even if you don’t consider all members of Homo to be human, they are certainly very similar and would be potential competitors.
Check borders. The Silk Road is Europe on one end and East Asia on the other. You get a spectrum of appearances all along it.
Nepal is a good example. A cross section of Nepali people looks like a mix of people from the Indian subcontinent and East Asia.
There’s sufficient migration to allow for mixing of phenotypes. But there’s rarely been the kinds of rapid, massive population shifts you’d need to homogenize the human race.
And “Indian” is itself a bit of a generalization. There’s a fair amount of genetic diversity on the Indian subcontinent. Dravidian language family speakers in the south of India look different from Indo-Aryan language family speakers in the north. And, to be sure, there’s a fair amount of mixing there, too, along with all the other mixing due to influences from other parts of the world (they didn’t just stay put, either).
People staying in Japan is also pretty much wrong. You have what we typically think of as “Japanese” and there’s also the indigenous Ainu (some of whom can also be found on Sakhalin). Both groups came to Japan independently and there’s been a fair amount of mixing between them.
Of course some of those people who traveled abroad had sex. There was human genetic information flowing all around the world. But that’s still true nowadays. People can travel from Japan to Egypt, or vice-versa, and have sex. Some people do so. But Japanese and Egyptian people still mostly look different. Why? Because the vast majority of them aren’t moving around and having sex; they’re just staying close to where they were born and having sex mostly with other people who stayed close to the same area.
I did not say anything about them mingling with each other, just that you have no reason to assume that there was no human movement in out of these (widely separated) regions, either through individuals moving in and out from nearby regions, or through mass migrations (either in or out) of groups.
There is an awful lot of territory between every human being equally likely to breed with anyone from anywhere else in the world (which would, presumably, completely homogenize all racial differences away) and nobody ever moving or interbreeding with anyone living more than a few miles away. The reality (in prehistoric times, and even now) is in between.
The genetic variations you see today would have been accumulating since the origin of our species. I think it’s likely that before agriculture was developed, when populations were small and peoples more nomadic, the variations would have been more “smeared” across the inhabited globe. People from place X would have looked different than people from place Y (had different observable traits), but you would have not been able to identify “races” because there were a lot of people out there with various combinations of those traits and no “look” predominated over more than a small area.
When a people in some little area developed agriculture there was a ballooning effect. Now people with a certain “look” expanded rapidly in population, swamping the populations of differently-looking people over larger and larger areas. Now you have large numbers of people who look like X, Y, and Z, which we now call “races”. There are smaller populations of people who don’t look like X, Y, or Z, either because they retain much of their pre-agricultural genetics, or they are a mixture of X, Y, and/or Z - or both.
Don’t forget about the potential impact of the apparent interbreeding with Neandertals and Denisovans. That could potentially explain a lot of the differences we see, as Caucasians have more Neandertal heritage, Melanesians (and some of their neighbors) have some Denisovan ancestry, and Africans don’t have much of either.
Neandertals are presumed to have split off from our common ancestor about 350-400k years ago, so there was plenty of time there for the development of different genes. If some of their genes provided advantages to Homo sapiens when they were introduced through interbreeding, they could have caught on relatively quickly. These advantages could have been something as simple as features that were perceived as more attractive, leading to their bearers producing more offspring.
Oh, and just think about the variety of dogs that exist… most of which came about in a matter of centuries. Of course, a generation of dogs occurs in a much shorter period, and there’s a lot more selection for specific traits, but it just goes to show what’s possible as far as mutations and gene selection.
Not necessarily. The culture can travel without the people traveling with it. In fact, biologists have been going back and forth about whether it was cultural diffusion or human migration that brought agriculture into Europe from the M.E. I can’t remember for sure, but I think the consensus now is that it was largely cultural diffusion.
Recent studies on ancient DNA have dealt a serious blow to the post-war pet theories of diffusion as the main mechanism of the spreading of agriculture. Evidence is accumulating that hunter-gatherers were in fact replaced by invading agriculturalists in Europe. Below are just a couple of quick links on the subject:
Do you really think that the Koreans and Japanese just sat in their own territories for thousands of years totally ignoring each other? Of course there’s been back and forth between the Koreans and Japanese. Archaeological evidence and written records show that the Japanese have been in contact with the Koreans and Chinese since the Yayoi period, if not before.
Do we know if the spread of farming in the different geographical areas always resulted in population replacement rather than cultural expansion w/o population replacement?
