I am not so much suggesting it (the former not the latter), so much as asking if it is an open consideration. As to how modern cladastic systems work, well it would suggest that the clade of birds would have to go much farther back to find a last common ancestor. It is asking if perhaps some modern birds may indeed have lineage that goes to Tyranoptora, let alone less improbably some other lines of Maniraptora, and converged upon the modern forms. The fact that Archaeopteryx may indeed be a representative of a proto-bird appearing creature appearing from a line that diverged relatively early, raises that “bird” as a convergent evolutionary form among several dinosaur lines as a possibility.
Again, I suspect that there are reasons why it is not so, but would like to know more than “fear not” as an answer.
As to the second, well that depends on where you draw the species line, doesn’t it? We know now, for example, that some sub-populations of Homo Sapiens have some Neandertal genetic contribution mixed in. But, no, that was neither my suggestion or my question.
Alright. I’m going to attempt to answer my own question.
Studies of genetic relatedness among modern bird groups establish their evolutionary distance from each other to some significant degree. One study here.
A great many species have combined over time. Our own species, for example, split from Homo erectus into the Sapiens line and the Neanderthal line, and then recombined. There is a large school of thought that suggests a merging with erectus lineages and several other as as well.
This merging of related species is extremely common, and we can see it clearly happening even today with animals such as ducks and cattle that humans have been moving around inaddition to mergng of natural populations due to disruption of natural systems, such as the merging of wolf and coyote or grey/blue/humpback whale populations.
Amongst plants this merging of lines is the rule rather than the exception, with very few plant species being descended from a single parental species.
While lines of descent are often illustrated as a tree, the reality is that the branches often split only to re-merge hundreds of millions of years later.
It’s certainly not inconceivable that the modern birds have multiple non-bird ancestors. There is a widely supported hypothesis that all the animals we call “bats” have descended from at least two non-bat ancestors, with the fruit bats descended from a Colugo-type ancestor well after the true bats had already evolved flight.
Yes. In fact, all modern birds are from a relatively late split well within the clade “Aves” as diagramed by Darwin’s Finch, and long after that clade split from the non-avian dinosaurs. There are a number of Cretaceous lineages within the Aves that have become extinct, such as the Hesperornithes andEnantiornithes.
The ostriches and other ratites along with the partridge-like tinamous are thought to be the sister-group of remaining birds; but they are no more related to non-avian dinosaurs than other birds are.
Doesn’t that depend on how you define “species”, though? Under at least some definitions, the fact that there was a merger would itself be evidence that they were never actually separate species to begin with.
Neanderthals are part of the sapiens line. Their distinction from Homo sapiens sapiens is certainly much later (and briefer) than the distinction of archaic sapiens from erects.
It’s very likely that there used to be several such groups, that when you looked at them flying around covered with feathers, you’d call them birds, but you’d find they weren’t part of the modern bird clade. However, all these bird-like flying feathered lineages went extinct at the end of the Cretaceous. All modern birds turn out to represent a sole surviving closely related group.
Like “fish,” it would be possible to use “bird” in a non-taxonomic sense. What we call “fish” colloquially belong to several different clades, including hagfish, lampreys, sharks and rays, bony fish, and lobe-finned fish (and we ourselves are members of the latter clade), so the term has no taxonomic meaning. A “fish” is just an aquatic, gill-breathing vertebrate. Likewise we could call any feathered, flying member of the therapod lineage (or a non-flying descendant of one) a “bird” in a colloquial sense. According to this usage, Archaeopteryx and Microraptor would qualify as birds, even though they don’t belong to the lineage that led to modern birds.
I wouldn’t call what happened between sapiens and neanderthalensis a merger, exactly. We have only a few Neanderthal genes, and those are only present in non-African members of sapiens. This suggests very limited interbreeding in the Middle East when sapiens first left Africa. During their long period of coexistence in Europe the two lineages seem to have acted as full species. According to the modern interpretation of the Biological Species Concept, the two lineages could still qualify as full species, because hybridization was limited in space and time.
No. Neanderthals are still considered a distinct species: H. neanderthalensis. They are thought to have split off from our line about 500 -750K years ago. That would predate what is often called “archaic sapiens”. But they are thought to have emerged as a species from that split about 250K years ago.
Has it been established that the interbreeding was restricted to the M.E.? I hadn’t seen that in any of the articles.
I haven’t looked at the articles recently, but based on the age of the Neanderthal genes in sapiens (that is, when the form of the gene in sapiens split from the form found in Neanderthals) the interbreeding dates from a time when sapiens was restricted to the Middle East (outside of Africa). Also, the genes occur in sapiens populations outside the range of neanderthalensis, such as those in east Asia, implying that they were acquired before sapiens spread to these areas.
Considered by some. They are also termed Homo sapiens neanderthalensis–a subspecies, as distinct from H. sapiens sapiens.
My understanding is that the Neanderthal distinction has not been clearly made until 130,000 years ago or so, which may or may not be before the earliest “modern” sapiens depending on interpretation (Herto?), but is certainly very far after H. erectus, who is back past 900K. There’s no way that Neanderthals could precede “archaic sapiens” unless you’re defining archaic sapiens out of sapienhood entirely.
Considered by most. But the whole business of defining species for extinct populations is problematic. Still, you don’t see H. sapiens neanderthalensis very often.
The whole “archaic sapiens” concept is very ill defined. I’m really not sure what you’re trying to say here, but H. erectus is usually used for Asian branch of the *Homo *line, and that survived until perhaps 30K years ago.
I’ve never been fond of these squishifications of the BSC. I mean, breeding within the Neanderthals themselves was also limited in space and time, since they had a limited geographic range and went extinct. Likewise, I also don’t like to call it “speciation” where the only reasons for a lack of interbreeding are geographic, since by that standard, Native Americans and Afreurasians were separate species until contact was re-established.
Yes and no. It’s true that there was limited gene flow between Native Americans and the rest of the world for (let’s say) 15k years, but there was limited or no gene flow between Neanderthals/pre-Neanderthals and Sapiens/pre-Sapiens for ~500k years.
It would be extremely unusual for a long lived, slow breeding mammal like us to speciate in 15K years.
Additionally, Neanderthal morphology falls well outside the morphology of modern humans and there appears to have been a significant cognitive difference between the two populations.
Finally, there appears to have been a difference in the maturation rate of Neanderthal children wrt modern humans.
So, when you put it all together: Geographic isolation, morphological differences, cognitive differences, and differences in maturation rates, then the argument for species designation is pretty strong, and not really in the same ball park as one for saying Native Americans pre-contact should be considered a different species.
But in the end, it just comes down to how we choose to define things. Nature doesn’t care one or the other.
We can only infer this from the archeological record, but the Neanderthal tool kit was simpler w/ fewer materials used, and appears to have been static over an extended time period. We don’t seen needles, fishhooks or spear throwers, for example. Stone tools, but not bone/antler tools. But more significantly, we don’t see any evidence of representational art.
Now, it’s possible that there are items made of wood that simply didn’t survive the fossilization process and that might change our view of the Neanderthal intellect, but the evidence we do have tells us otherwise.
All species definitions are necessarily “squishy” since species in their incipient stages are difficult to define. Without such “squishification,” we would be compelled to define wolves and coyotes as the same species, as well as many species of common ducks, since they do sometimes produce fully fertile hybrids in the wild (although such hybridization is limited in space and time).
Presuming that the Aurignacian culturebelongs to early modern humans, this implies an overlap of about 10,000 years between sapiens and neanderthalensis in Europe without genetic evidence of interbreeding. This constitutes is a very long period of coexistence over a very wide area; if a similar pattern were found in two contemporary forms of mammals I would hesitate little in calling them good species under the Biological Species Concept.
Geographical isolation by itself does not provide evidence of species status. However, Native Americans and Eurasians/Africans show much less genetic and morphological divergence than that between all sapiens and Neanderthals.
Neanderthals show very little evidence of art or other kinds of symbolic thought, although there seems to be some. Symbolic thought, decoration, and representational art are a hallmark of modern humans.
