The problem is that speciation is both horizontal and longitudinal. What do I mean by that?Falco Knotwise wrote: ↑Thu Dec 14, 2023 12:14 pm Hilaire Belloc accepted evolution in a sense, but insisted that each species was a new creation.
That remains vague and philosophical for now, but I think it’s also what Eric Voegelin argued in substance. It remains a problem for philosophy but I’m inclined to agree with this intuitively.
First horizontal: a single species can branch into several different species which usually is the result of geographic separation. So, for example, both polar bears and grizzly bears are thought to be descended from a single ancestral brown bear species originating from Europe (probably Ireland) during the ice ages (Pleistocene) maybe 500,000 years ago. So you have one ancestral species splitting into two new species. And one can probably find the point in time when those two different bear populations diverged enough to effectively became separate species.
Second, longitudinal: Sometimes a single species can change over time due to changing habitat or conditions without branching. The evolution of the modern horse would be an example. In this case, paleontologists might identify and name various intermediate fossil species. But the identification of different species is really an artificial construct since there is really just one long continuous process. And the intermediate species that are named are largely just a consequence of the fossils that are found and identified. It is kind of like the color spectrum. How many colors you identify in the spectrum is arbitrary. Do you skip from red to yellow or do you include all the various shades of orange as well and consider them separate colors? Just like how many species you identify in a longitudinal sequence and where you place the break points is also arbitrary.
In point of fact, both processes tend to happen at the same time. So in the case of the horse we had both horizontal changes (branching) and longitudinal changes.
The larger point is that the notion of "species" itself is an artificial construct. In nature, different plants and animals don't have their own name tags identifying them as different species. That is just the result of the human desire to sort and classify and make order out of the world that we observe. It works pretty well, but the world is really more complex than that and there are always exceptions and complications. And there are many longstanding debates about whether different populations should be considered different species or subspecies. That is going on now with salmon originating form different ancestral streams and rivers. For example, are the Chinook and Coho salmon in the Klamath River in California a different subspecies from those in the Columbia River in the Pacific Northwest, or the Yukon river in Alaska?
Nature doesn't always sort itself into tidy and neat categories simply to accommodate the human desire to classify, name, and sort things.
