Taxonomy is a wild world, exactly because species are human inventions. Taxonomists can generally be classified as 'joiners' (who advocate for fewer species) and 'splitters' (who advocate finer divisions). The linked article is written by a splitter. "Can't produce human speech sounds" seems like a good indication that a split in human taxonomy is worthwhile, though.

They are, in the same sense as “rain”, “fog”, “snow”, or “sunny weather” are human concepts, and not natural low. After all, these are invented by humans, blurry on the edges, and sometimes overlap.

Sure, but that isn't the point, the point is that if you manufacture categories, you shouldn't then reason forward from the manufactured categories.

"It's snowing so there can't be unfrozen water in the air" or whatever.

Is it? I always thought that species is defined as a group that can have fertile offspring.

Horse and donkey, for example are not the same species because their offspring, a mule, is not fertile.

It breaks down with edge cases. There are a few documented "ring species" such as a diverse land-based amphibian around a lake. At all points the adjacent neighbours can mate, but if you take examples from the far side of the lake, they cannot. One species? Two? Infinite?

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.

A ring species is an example of a species complex, and subpopulations with different but not mutually exclusive breeding compatibility are known as microspecies. If populations with distinct morphological features are isolated in space or time but could still interbreed with eachother if they were to be brought into contact, they are subspecies.

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.

It’s the ‘what’s a sandwich’ problem, which is hard. Is a stack of pancakes a sandwich? Is a stuffed pita a sandwich?

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.

If you eat two pancakes with butter between like a sandwich, it is a variant of butter sandwich. If you cut up your PB&J such that you're only eating pieces of bread with some spread on them, that is not a sandwich. The bread must act as a container for the contents during consumption, regardless of ingredients.

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.

You're carving out a definition to fit intuitive inferences gleaned by observing instances of "sandwich" and "not-sanwich" labeled by influential people in your life who had no objective reasons for constructing and perpetuating those categories in the first place.

I agree it would have been a lot easier if we precisely defined the sandwich before foods were invented so we'd know which category to place them in ahead of time, but alas barring the invention of time travel we have to deal with our forefathers' mistakes.

But what about the named club sandwich, which 1) has a width to height ratio so unfavorable it needs toothpicks to hold it together, and 2) often has more bread than ingredients (at sub-par establishments), but sometimes far more ingredients than bread (leveraging the toothpicks).

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!)

It's not the thickness of the sandwich, it's the thickness of the individual things in the sandwich. Everything in a club sandwich is flat, there's just a lot of stuff.

Many club sandwiches have folded ingredients (with a big loop in it) [https://www.spendwithpennies.com/club-sandwich/]

(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.

You've never thought open faced sandwiches were a subset of sandwiches?

This definition includes open faced sandwiches so long as their contents have the appropriate aspect ratio and you hold them via the bread. If you needed two pieces of bread to make a sandwich then that would rule out everything served on a roll. Pizza is an open faced true sandwich, pancakes are not.

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.

The aspect ratio rule fails for a bagel-with-cream-cheese from a NY food cart, clearly a sandwich, which has a square of cream cheese which is as large as the bagel in 2 of 3 dimensions.

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.

But it has 1 dimension, it's thickness, which is substantially smaller. You don't have a cube of cream cheese, you have a thin square. Thus it satisfies the aspect ratio rule, which, again, says there is one substantially smaller dimension than the other two.

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?

The usual non-prescriptive example is Platonic ideals.

https://en.wikipedia.org/wiki/Platonic_idealism

That’s a pretty interesting edge case.

Now that you’ve said this I do remember Richard Dawkins making that argument. That’s pretty compelling.

There are far too many edge cases (e.g. ring species), but it's also not practical. How are you going to decide whether two individuals can't reproduce together, or choose not to? What if all you have are some dead specimens?

It's mostly based on DNA analysis these days, I think.

Even if we limited ourselves to the Homo genus, the rule does not work well.

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).

You get the occasional fertile mule!

Oh interesting. I had no idea

Theoretically that wouldn't be a killer issue, since fertile mules are extremely rare, so you could refine the definition to say "is very very likely to produce fertile offspring" (while horses and donkeys breeding is not).

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).

If neanderthal or denisovan genes were ancestral, you would be able to find them broadly in African genomes and some of them wouldn't carry adaptations to environments not found in Africa. Instead they reinforce (and inform) our understanding of early human populations out of Africa.

How do you actually test that as a working ecologist, though? Given two geographically and somewhat morphologically district warblers (for example) you would need to convince two of them to breed (after capturing at least one) and then check viability of an offspring. It's not terribly practical...

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.

I think the fertile offspring test would say a lot of these humanoids aren't different species, though?

Is the domestic dog the same species as the coyote or wolf?

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...