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No doubt there were differences between Neanderthals, Denisovans, and 'Sapiens' (and I've never understood why differences in brain case size are considered significant), but what I'm mainly concerned with here are definitions, i.e. how much difference is possible within a 'species'.
Brain case size was a metric/shorthand for intelligence and there is a correlation between cognitive abilities and size/ complexity so early hominids ( think Lucy and the Australopithecines ) did not have the same level of complex reasoning ability that Sapiens, Neanderthals and all the other undiscovered relatives undoubtedly did.
They were however different species albeit very closely related whereas obviously all living human beings are members of the same species.
There is evidence of relatively low interbreeding ( I’m going to stick with that as it’s the scientific term, although I share your distaste of its appropriation by those trying to ‘scientifically’ justify their racist nonsense) between Sapiens & Neanderthals shown by the genetic transmission of Neanderthal genes - less than 2% . ‘ We find that observed low levels of Neanderthal ancestry in Eurasians are compatible with a very low rate of interbreeding (<2%), potentially attributable to a very strong avoidance of interspecific matings, a low fitness of hybrids, or both‘.https://doi.org/10.1073/pnas.1107450108
I think establishing beyond doubt that there have never been any really significant differences between people would help to some extent with the fight against racism.
Yes absolutely agree and in fact would qualify this to extend the notion of personhood to other forms of life and outwards from Homo Sapiens who as you point out are significantly the same but that is of course another debate
Big_Nick-
Brain case size was a metric/shorthand for intelligence and there is a correlation between cognitive abilities and size/ complexity so early hominids ( think Lucy and the Australopithecines ) did not have the same level of complex reasoning ability that Sapiens, Neanderthals and all the other undiscovered relatives undoubtedly did.
I wouldn't doubt that, but I'm much less concerned with those remote ancestors, much more so with the later groups. As you say, I doubt very much that there was a lot of difference between them.
They were however different species albeit very closely related whereas obviously all living human beings are members of the same species.
But what is this tied to? At what point do you establish a different category, e.g. a species barrier, if the fertile offspring explanation doesn't work?
There is evidence of relatively low interbreeding ( I’m going to stick with that as it’s the scientific term, although I share your distaste of its appropriation by those trying to ‘scientifically’ justify their racist nonsense) between Sapiens & Neanderthals shown by the genetic transmission of Neanderthal genes - less than 2% . ‘ We find that observed low levels of Neanderthal ancestry in Eurasians are compatible with a very low rate of interbreeding (<2%), potentially attributable to a very strong avoidance of interspecific matings, a low fitness of hybrids, or both‘.
Well, this kind of genome analysis work hasn't been going on for very long, and consequently shows a wide variation. I'd give it some time before it can settle on solid conclusions. As I've said before, I strongly suspect that Neanderthal populations were always small, certainly much smaller than the populations stemming from the sub-tropics of northern Africa, where I suspect populations exploded in size at some point (conditions there probably being ideal for humans until the environment began to deteriorate), or at least caused sufficient overpopulation to cause waves of migration--the main reason why there was such a long gap between the migrations of groups who made up the Neanderthal population being the Mediterranean. Without better estimates of population sizes in ancient Europe as well as the size and impact of migration, I think calculating any 'rate of admixture' isn't going to be very reliable.
I think establishing beyond doubt that there have never been any really significant differences between people would help to some extent with the fight against racism.
Yes absolutely agree and in fact would qualify this to extend the notion of personhood to other forms of life and outwards from Homo Sapiens who as you point out are significantly the same but that is of course another debate
Yes, I've been following that debate for many years. People like Peter Singer have been involved in that drive. My own take on it is that it absolutely shouldn't require a designation of 'personhood' to stop animal abuse, although I'm very sympathetic to extending our 'circles of meaningful responsibility' based on similarity, especially to Great Apes. It just strikes me that anchoring it in personhood is a pragmatic idea based on the legal systems that exist, and that even were we to extend it to Great Apes, that would implicitly legitimise the slaughter of animals denied the designation. It might well eventually be extended further outwards, but I'd rather we first understood why animals are worthy of a protected status, and I don't just mean mammals, but also birds, fish, and insects. Still, it's a debate worth having. I don't know what would bring the greatest benefits most quickly, either. Obviously, to fight racism you don't need to extend to any of this.
Oliver Schick
Yes, the myths definitely need busting. To explain what I mean a little more: No doubt there were differences between Neanderthals, Denisovans, and 'Sapiens' (and I've never understood why differences in brain case size are considered significant), but what I'm mainly concerned with here are definitions, i.e. how much difference is possible within a 'species'.
(NB I also don't like using the word 'interbreed' when speaking about people, although when I first started to think about this, I used it myself.)
Now, I realise this may not be current thinking any more, but I always thought that 'species' was defined as 'can produce fertile offspring with one another', between male and female in the case of mammals, for instance. All I've ever read suggests to me very strongly that all human groups were able to produce fertile offspring together, and that they are all woven into our story. I seriously doubt that any group of humans ever fully 'died out' or 'became extinct'. Sure, they bashed each others' heads in all the time, like humans have always done, but they also produced fertile offspring.
My question has long been how much difference remains after that to still call different humans members of different 'species'. What does 'species' mean if it's not special enough to procreate alone? I strongly suspect that it's simply inapplicable to humans. I think that if we were to find any evidence of different human species, it would be in the very early stages of our evolution, i.e. probably in Africa, but probably not outside it. Obviously, we have various extremely old fossils from across a long, long period of time, and it's possible that those at the start of the development would not have been able to produce fertile offspring with those at or towards the end of the chain, because by then significant enough changes in their composition had taken hold, but I think it most likely that people would always have been part of one contemporaneous species.
Again, I'm no expert, just an armchair conjecturist, and one reason why I care about the answer to this is because I think establishing beyond doubt that there have never been any really significant differences between people would help to some extent with the fight against racism.