[lunaru]

Speciation of archaic humans is an attempt at applying discrete categorization to continuous phenomena. It's like looking at a rainbow and trying to figure out where red ends and orange begins. Also interesting is Homo Longi, which can be argued to be Denisovan, or maybe not, depending on where you want to draw the lines on the raindow: https://en.wikipedia.org/wiki/Homo_longi

[nkrisc]

The lines are arbitrary, but it may still be useful to draw them for some applications.

It’s a rainbow all the way back to the first tetrapod (and beyond). But clearly we are not fish, so somewhere in that spectrum there is a useful distinction to be made, a line to be drawn. Of course, the closer you get to finding that line, the faster it vanishes. It’s equally futile to say that we are indistinct from fish because there is no clear and decisive separator.

[lazide]

Yup, same with drawing lines on a rainbow.

The concept (and definition) of red, orange, etc. is important and useful. A great many things would be impossible without it frankly. [https://en.m.wikipedia.org/wiki/Spectroscopy]

Applying it in real life in some situations sometimes has a fractal like quality. Like measuring a shoreline.

[throwup238]

I’ve gotten the impression from several practicing archaeologists that the biggest reason they haven’t unified a bunch of the Homo species is that no one can quite agree on how to do it and there’s so much inertia in the field. Between ample evidence of interbreeding, the growing evidence that our genetic differences weren’t that significant compared to modern variability in the human gene pool, and a reevaluation of morphological differences it’s getting harder and harder to justify keeping them separate.

[Amezarak]

As a sibling comment mentions, this is true for pretty much all animals. It's a well-known, old problem. Darwin even mentions it in the Origin of Species and says that "species" is really just a term of convenience applied somewhat arbitrarily according to the different tastes of different naturalists.

Now we understand even better that, like GP said, there are no discrete groupings we can label as a species. It's a useful abstraction at a 5000ft level but it breaks down when you zoom in.

[colechristensen]

All speciation is this. It’s muddy and not all that useful for the intermediate stages between one species and two.

[mensetmanusman]

There are definitely red and orange colors though…