Modern biology has moved on from the definition of a species being able to breed functioning offspring, since it's actually pretty fuzzy- e.g. with ring species https://en.wikipedia.org/wiki/Ring_species
I'm not sure your comment is relevant to the discussion. The concept of species, when it involves sexual reproduction, is pretty straight-forward: mating produces fertile offspring.
Your remark is only relevant when nit-picking corner cases involving asexual reproduction, which I don't expect to be the case in Neanderthal-Human cross-breeding.
It really isn't. In higher mammals the basic property of generating fertile offspring through sexual reproduction is clear-cut and undisputed. The only discussion there is in the species problem is in reaching consensus on a general definition that is common to all taxonomy levels and regardless of type of reproduction.
Hence the species problem being a debate regarding generic traits, and which should count and not count, hoping to form a common definition.
If you haven't read the literature just say so. This is an actual topic of debate between real anthropologists and has been for decades. I think everyone sort of got tired of hashing it out with all the recent tree-rewriting going on, but it's still unresolved.
They still have a valid point in that we don’t have a better definition of species than sexual compatibility. One could construct a theoretical ring species that encompasses all life on earth If the inner connections have not gone extinct
> "In higher mammals the basic property of generating fertile offspring through sexual reproduction is clear-cut and undisputed."
What's undisputed is that there are plenty of species that can and occasionally will interbreed, and yet are still considered separate species. Wolves and coyotes, for example. Horses and donkeys are famous for producing infertile offspring, but occasionally, that offspring is still fertile.
So it's not a clear-cut on/off situation. There's a gradual scale from fertility to infertility. The edges of the old definition of species can get very fuzzy. For this reason, biologists these days tend to talk more in terms of populations than species.
It's not easy to define species following a common basic definition that applies to all taxonomy ranks, specially when asexual reproduction takes place.
But this is not the case being discussed here.
With higher mammals that is not the case, and the definition of species is already well established: sexual reproduction results in fertile offspring.
Riddle me this, you have 2 populations containing 2 sub-populations each. Lets call them populations Aa and Bb. 'a' can mate with 'b' and produce c. c can produce viable offspring with A or B but A and B can not produce viable offspring. What do we call Aa and Bb if not distinct species? What do we call c?
What if some members A can produce viable offspring with B some of the time but not always? What then? My point is we make taxonomical distinctions for our convenience, they don't really have any hold on the natural world.
By this definition, are a chihuahua and a great dane the same species? With artificial insemination they would certainly produce fertile offspring, but they could almost certainly not do this naturally.
That seems to kick the issue down the road. It defines 'species' clearly, but it doesn't make it clear how to assess 'fertile reproduction', or why it should be the criterion.
Discovering a new hominid species gets you on the cover of National Geographic. Discovering a new specimen in a previously-identified hominid species does not. So, in general, the field of biological anthropology has leaned towards identifying new species when possible.
Svante Paabo, who led the group that sequenced the Neanderthal genome and discovered we interbred with them, had to decide whether to give a species- or local name to the Denisovans. The argument that carried the day was that “species” is such an ill-defined biological concept that it’s a sterile intellectual exercise arguing over it; and if they’d gone with, say, Homo altaiensis rather than Denisovans, it would’ve been extremely hard to take it back (“Neanderthal Man,” 2014, Ch. 23).
Considering Paabo secured funding from the German government for a brand-new research institute in ancient human DNA and related subjects, including the right to decide what city to build the institute in and hiring authority over the initial staff, and given that he had an advance agreement with Science to publish the Neanderthal genome, I think some of these discoverers aren’t that exercised by whether they make it onto the cover of National Geographic.
2. We can't actually test sexual reproduction of extinct "species"
3. Even if we go with the one definition of species which
is "largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring", evidence of some reproduction does not speak to how often such reproduction led to fertile offspring. For example "No evidence of Neanderthal mitochondrial DNA has been found in modern humans"[1], and "Neanderthal males might not have had viable male offspring with Anatomically modern humans females"[2].
> No evidence of Neanderthal mitochondrial DNA has been found in modern humans. This suggests that successful Neanderthal admixture happened in pairings with Neanderthal males and modern human females.
The full quote from [2]:
> A 2016 study presented evidence that Neanderthal males might not have had viable male offspring with AMH females. This could explain why no modern man to date has been found with a Neanderthal Y chromosome.
Also from [2]:
> Positive evidence for admixture was first published in May 2010. Neanderthal-inherited genetic material is found in all non-African populations and was initially reported to comprise 1 to 4 percent of the genome. This fraction was later refined to 1.5 to 2.1 percent.
Because the definition of species is somewhat circular. Two sets of organisms are separate species if they can’t interbreed with one another. So if there’s proof that humans and neanderthals had children together, we’re the same species. If there’s no such evidence, then we’re not.
This definition kinda breaks down when we realise that wolves and coyotes can interbreed in the wild to give birth to viable offspring.
A somewhat interesting fact is that by this definition two groups of humans can be different species simply by not being able to reach each other due to a impassable barrier
For historical and cultural reasons; you could also ask why North and South America are considered separate continents and why the Arctic is considered a continent at all. The tradional seven-continents model predates modern geology and is a mix of geological, cultural, and linguistic categorization. We might also divide them by continental plates, in which case Eurasia and Africa are distininct continents. Another approach is contiguous landmasses, which leads to a four-continents model which has Afro-Eurasia, the Americas, Antarctica, and Australia along with their associated islands. There are various other models; which you prefer depends on your definition of continent and your reasons for dividing them.
Who considers the Arctic a continent? Wouldn't that be like considering the Pacific or Caribbean a continent? And many people consider North and South America to be the same continent: https://en.wikipedia.org/wiki/Continent#Number
You're right that there is a definition by which “a different human race” is a sensible designation, but personally I think the concept of “race” belongs in the bin. There are many things we could sensibly call “æther”, yet we avoid the terminology because historical science papers used the word to describe a concept that's now so obviously wrong it's amusing that anybody ever thought it was the case.
Science always brings in modern-day politics. Science, in its purest form, doesn't know of silly human foibles like “ethical restraint” or “but that's almost certainly fatal”; if scientists acted purely on scientific inquiry, the scientists who didn't kill themselves in a hair-brained scheme would either be in prison or on the run.
The classification of humans into “races” is historically associated with pseudoscientific drivel that was never particularly based on reality (much, much less so than the idea of æther); even if you've found a “race” classification that actually does have an element of truth in it, giving it the same name as the Göttingen school's scientific racism is probably not a good idea.
