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Earlier quoted context omitted.
They can breed, but if I'm not mistaken the off-spring can't have off-spring of their own.
Lions and tigers can interbreed. Ligers and tigons are fertile: https://en.wikipedia.org/wiki/Liger https://en.wikipedia.org/wiki/Tigon https://www.youtube.com/watch?v=JE8Z5Es-M0E
If we interbred with them, how are they actually species? It seems more to me you're talking more about racial or breed differences akin to breeds of dogs if two species actually successfuly had viable offspring in the wild.
Major physical differences (such as wolf) or inability to interbreed or infertile offspring (such as mules) are all just rules of thumb. For instance zebras and horses are clearly distinct species yet they physically appear extremely similar sans their coloring, can interbreed, and there have even been instances of fertile offspring.
What is the difference between the genes identifies as "extra-species sourced" and those which are a nominal part of homo sapiens DNA? How do we know they don't originate from intra-species mutation, for example?
Again, I'm sure the real models get really complicated and are no doubt still a little controversial. But that's the basic idea.
This theory was one of the most interesting ideas in Sapiens , take a look at a model of what other great apes look like, if so many types of dog can interbreed why wouldn't these great apes?
This is misleading. Superficial physical appearance isn't always a good indicator of genetic similarity or sexual compatibility.
Earlier quoted context omitted.
Yeah, seems more logical to say ancient human experienced a number genetic divergences which were then folded into the mainline of the genetic stream.
Environment plays a huge role. If a nomadic group was in a jungle-like environment, wouldn’t they more likely develop the traits of the other species well suited for jungle living? Over a long enough timescale.
Well it does play a role, but in different ways. For instance modern humans are continuing to evolve even though natural selection, in terms of man against environment, is now playing very near 0 role. Instead the factor being selected for now is simple fertility. Humanity will tend to evolve along the characteristics of those families have 3, 4 and more children - while those having 2 or fewer children will gradually fade from the gene pool. So natural selection has in some ways become voluntary, which is quite paradoxical.
However in less developed areas, it's still alive in some ways. For instance if an individual in subsahara Africa somehow developed a genetically heritable mutation making him immune to malaria, it's reasonably likely that all subsaharan Africans would, gradually, become immune to malaria. We can only conclude, putting aside epigenetic factors once again, that such mutations are much less common than e.g. those to the shape of a bird's beak.
If we interbred with them, how are they actually species? It seems more to me you're talking more about racial or breed differences akin to breeds of dogs if two species actually successfuly had viable offspring in the wild.
Interbreeding isn't a bright line. Zebras can breed with Donkeys! https://en.wikipedia.org/wiki/Zebroid Darwin's Origin of Species had a good section on this; the book is quite readable.
Yeah, I recall Darwin discussing at length how there's no clear difference between a "species" and a "variety". It's a key point, so it's too bad that many people are still under the impression that "species" has an unambiguous definition.
Earlier quoted context omitted.
Interbreeding isn't a bright line. Zebras can breed with Donkeys! https://en.wikipedia.org/wiki/Zebroid Darwin's Origin of Species had a good section on this; the book is quite readable.
They can breed, but if I'm not mistaken the off-spring can't have off-spring of their own.
Earlier quoted context omitted.
Yeah, seems more logical to say ancient human experienced a number genetic divergences which were then folded into the mainline of the genetic stream.
Environment plays a huge role. If a nomadic group was in a jungle-like environment, wouldn’t they more likely develop the traits of the other species well suited for jungle living? Over a long enough timescale.
Suppose we found enough DNA to recreate these hominins. Would they be citizens or zoo animals? Either way, what if they want to interbreed? Do we determine this based on looks? What if the attraction is unidirectional?
Some of these species are thought to be smarter than us, so you better be careful or you will end up the specimen in the zoo.
Contrary to pop media, there is also literally no clear evidence they even engaged in the most basic of symbolic behavior such as self adornment or even primitive art. [1] Now mostly disregarded efforts to show such were highly optimistic. This included things like bird bones being laid near a corpse = self adornment, or scratches on a cave floor = art. Even in what they did do - hunt, despite engaging in hunting for hundreds of thousands of years there are extremely high rates of traumatic injury among neanderthal corpses which suggests they never even managed to refine their hunting ability.
And the brain size : intelligence correlation is just so broken in so many ways. If you go based on raw size sperm whales should be, by far, the most intelligent species there is. If you go based on the ratio of brain matter to mass, ants should be, again by far, the most intelligent species there is. Suffice to say you're probably not too worried about being put in zoos by sperm whales or ants.