Keep in mind that species is a human concept and not some natural law.
"It's snowing so there can't be unfrozen water in the air" or whatever.
Horse and donkey, for example are not the same species because their offspring, a mule, is not fertile.
The bigger problem are things that have massive morphological differences but can still successfully interbreed, such as dogs, coyotes and wolves. They produce fertile hybrids and there is good evidence that this occasionally happens in the wild, but nevertheless it is rare and they have clear, stable morphological distinctions, even in areas where they overlap.
Even worse, that definition is entirely useless for paleontology, as it is impossible to know if two individuals species could even interbreed, nevermind knowing if their offspring would be fertile. Even modern genetic evidence (which is extremely rare for fossils anyway) is very open to interpretation on the matter of potential interbreeding ("Neanderthal" genes in modern humans could more or less as easily be common genes older than both H. Sapiens and Neanderthals - we have far too little evidence to be sure, and no chance of genetic material from an older ancestor).
I think it was Richard Dawkins who extended this idea through time. We could mate (sorry) with our immediate ancestors, who could with theirs, etc. and in fact there's a continual chain like that all the way to any other mammal. When did we stop being our ancestral species and become H. Sapiens? No clear line.
Now that you’ve said this I do remember Richard Dawkins making that argument. That’s pretty compelling.
What is it that makes a PB&J clearly a sandwich, and excludes a stack of pancakes with butter in between - and doesn’t exclude a club sandwich.
More generally, the key delimiter for sandwiches is the aspect ratio of the individual items contained by the bread. For something to be a sandwich, all of the major items inside must have one dimension which is substantially smaller than the other two. Sliced meats, bacon strips, cheese slices, sliced vegetables, lettuce leafs, spreads, patties, etc are all valid. Thinly spread peanut butter and jelly between bread is a sandwich, but a bread bowl with a pool of jelly and peanut butter where the depth is comparable to the radius would not be a PB&J sandwich. Flat cheese slice between bread is a sandwich, mozzarella sticks are not sandwiches. Hot dogs are by default not a sandwich, but if you cut the hot dog into thin strips it becomes a sandwich. An oreo is a sandwich but a quadruple stuffed oreo is not. The only commonly accepted sandwich which this definition claims to be a pseudosandwich is the meatball sub.
That said, just because something has a word in the name doesn't mean it's a subset of that category. Strawberries aren't berries, english muffins aren't muffins, prairie oysters aren't oysters, black pudding isn't pudding, etc.
I don't really get how your prescriptive rule means open faced sandwiches somehow "contain" their contents. Then again, since I don't believe in being prescriptive, I don't really care to think hard enough about the contortions of logic required by your approach.
A container is something which contains. If you can manipulate something by the bread part and the contents stay put, they are contained. While the aspect ratio rule may be legitimately controversial, if you don't restrict your definition of sandwich at least to stuff contained by bread then what isn't a sandwich?
The whole point of this exercise is to taxonomically categorize foods as being sandwiches or not sandwiches, how would you do that without being prescriptive?
Regardless of these facts and it not meeting your criteria, it is still both in common usage and by explicit name a sandwich!
(Also, love it!)
(Sorry, can't resist keeping this going, this is some good discussion).
It's true I guess that the aspect ratio for most ingredients is 'flat', but many are thicker than the bread, and the whole sandwich is 'sideways' aspect ratio wise.
This is really just an instance of Sorites paradox. But the inability to draw a precise line between two (or more) states does not mean there aren't two (or more) states.
Based on the admixtures of Neanderthal and Denisovan DNA in modern humans, we once had a lot of sex with those other humans (and they with us), resulting in fertile offspring, but the differences between us and them are pretty meaningful and probably worthy of not considering us and them just subspecies of the same species.
For example, Neanderthals probably could not vocalize in the same way that we do; and being capable of speaking is quite an important distinction. They had very different anatomy, including that of important joints (shoulders).
It's mostly based on DNA analysis these days, I think.
All can interbreed all can have fertile offspring with each other. Then look at the genetic variation between all three species.
Yeah this type of science is the stuff which destroys careers...
Or, in this case with ancient human remains, there's no way to check viability when all subjects have been dead for a hundred thousand years.