Mysterious ‘super-archaic’ populations had multiple trysts with human ancestors

Sure! I mean, I'm an amateur myself, mainly having become interested in the subject because of my ongoing fascination with wasps. But, being also an old birder, I wanted to develop a general sense of what "kind" of wasp I'm looking at when I see one, the same way I can tell an accipiter from a buteo from an osprey. That's turned out to be a surprisingly complex proposition! So here's what I've learned about taxonomy and cladistics as part of my research into wasps. Again, I'm an amateur, so if any actual molecular taxonomists should happen by, I hope they'll correct the goofs I am surely about to perpetrate.

Taxonomy, a specialization of biology, is the study of how organisms can be usefully classified. A major aspect of that study is the determination of how species are categorized, and how ancestral relationships are recognized. When this is done through molecular phylogeny (ie direct analysis of genetic relatedness and ancestry), the result is a directed graph called a "phylogenetic tree", whose nodes denote species and whose edges denote descent. Such a tree is called "monophyletic", meaning that it contains both, and only, a specific common ancestor and all descendants of that ancestor. Any subgraph from a single node of a monophyletic tree is also monophyletic. In this way, it's possible to establish a relatively unambiguous understanding of descent and relatedness among possibly widely varying organisms.

There are other kinds of classification which often produce groupings that make an intuitive kind of sense in terms of similar characteristics and the like, but which don't accurately represent relatedness. The Linnaean taxonomy is one of these, and the two terms used in cladistics to describe its categories of error are "paraphyly" and "polyphyly".

A paraphyletic grouping is one which contains a single common ancestor, but fails to contain all of its descendants. Many hymenopteran families are like this, such as Crabronidae, which is "all Apoidea that aren't bees" - bees and ants being actually descended from basal wasps, which were themselves descended from an even more basal shared ancestor with modern sawflies. Paraphyletic groupings can be useful, but aren't to be relied upon to accurately describe descent, and are replaced with monophyletic groupings as the necessary research and analysis is performed.

A polyphyletic grouping is one which fails to contain a common ancestor. For example, the European paper wasp (P. dominula) and the eastern yellowjacket (V. maculifrons) closely resemble one another in size, body shape, markings, and much behavior. Based on that, a Linnaean taxonomist might classify them as separate species within a single genus. This (hypothetical) genus would be polyphyletic; while these two wasps are indeed closely related, they're not that closely related, sharing a common ancestor with several other genera including all other social wasps and a sizable fraction of solitary species.

How exactly this all relates to the concept of "species" is hard to really define, at least for me as an amateur, but I think maybe also for professionals in the field. The classical definition, that a species consists of all individuals able to interbreed and produce fertile offspring, and none which cannot, fails to explain cases like wolves and coyotes, lions and tigers, or horses and donkeys - all pairs which are classified as separate species, but nonetheless are able to produce fertile offspring at least some of the time. Phylogenetics offers a distinct species concept [1], defining a species in terms of interrelatedness and innovation in traits as compared with ancestors - I suppose the classical definition could be called "horizontal", while the phylogenetic one could be called "vertical". Notably, the phylogenetic species concept appears to place no significance on interfertility or the lack thereof, which would mean that Equus, Canis, and Felis are not necessarily paraphyletic at all - they might be, but that wouldn't be defined on the basis of interfertility.

In the limiting case, I suppose that means each individual organism could be considered to constitute a unique species, although that is probably nonsense and certainly too granular to be useful. In any case, I hope all this answers your question, and provides some ground for further study. I've certainly learned something today, just looking up references! Thanks for the impetus to further systematize my understanding of the subject.

[1] https://www.oxfordreference.com/view/10.1093/oi/authority.20...

The point about the most recent common ancestor is well taken, but, at least according to my layman's level understanding of ring species, the two ends of the "ring" aren't expected to interbreed. Wikipedia supports that definition (and if it's wrong, should be updated by someone more knowledgeable than myself).

Evolution may of course be ongoing but not speciation in the sense of splitting into different species as we are now constantly mixing.

Speciation processes may return once we start colonising other planets as it is highly possible that physical contacts between populations will stop.

>I always wondered if there could be some sort of in-world explanation as to why all the aliens in star trek/wars are so ...humanoid.

I'd say that for most Sci-Fi Movies/TV there's a couple of reasons:

1. Non-humanoids are less relatable than humanoids;

2. Budgetary restrictions and the relative immaturity of CGI holds us back from creating fairly realistic and relatable alien species.

its not a secret nor disputed that the definition of a covid19 death is anyone who happens to die and is also covid19+. its also no secret nor disputed that many hospitals have and still calling any respiratory death a covid19 death without testing if they are covid19+. even public health officials calling for forever lockdowns acknowledge at least half of all of the covid19 deaths would have died in 2020 regardless.

It also didnt help that our health system was killing covid19 patients by giving putting them too aggressively on respirators. it's an inconvenient truth you get shouted at for bringing up.

Even with these absurd metrics for mortality, its clocking in at .3%. So in my opinion, its in the same weight class as the flu, but if you have such a problem with it, that's why I qualified the statement as I said it, depending on what your threshold is.

Keep in mind, the flu at the end of 2019 going into 2020 was a particularly bad flu. the mortality rate of those going to the hospital was around 6% according to the CDC.

it would not be 100 times worse than the flu. we have so much data on covid19 now, and nothing has really changed since the cruise ships, which was basically a free experiment for the world that has been promptly ignored over and over.