You asked for it. This will get long and I’ve honestly put too much work into this but here goes.
So first thing first, to understand this concept you need to know how a phylogenetic tree works. A phylogenetic tree is a diagram of what species are related to what, and uses branches and nodes to show this. Real trees can get very large and complex, but let’s start with this example with 4 species.
Is species B more closely related to species A or to species D? Looking at the edge you’d assume A, because it’s closer. But in reality A and B are the least related of the group- they have the farthest common ancestor. The common ancestor is the node at which the branches split. Trace backwards to the split that contains A and B and you’ll find it’s all the way back at node 1, while the split that contains B and D is the closer node 2. The closer the common ancestor, the more you’re related. B and C are the most closely related of the group, because they share a very recent common ancestor. A, being the furthest related from B/C/D, is the outgroup.
Another concept that people find hard to grasp is that just because two animals look similar, that does not mean they are related. Relatedness is determined by evolutionary history, shown by shared structures. Shared structures that are also seen in the most recent common ancestor are called homologous, and they can show an evolutionary relationship. An example could be the tooth structure of a lion and a cat. However, sometimes two unrelated animals come up with the same idea on their own. Birds, bats, and butterflies all have wings, but they all arose independently- the most recent common ancestor of all those was VERY far back and definitely did not have wings. Those non-related but similar structures are called analogous. You cannot compare them as if they are proof of being related.
Mammal natural history is especially tricky with this. These two tiny mousy things: (A vole and a shrew)
Are MUCH more distantly related than these two: (A deer and a dolphin), who some argue are even in the same order.
(Images from Wikipedia commons)
Okay, so that’s the science lesson for the day. But what does this have to do with ravioli? Well, you can track the history of food somewhat similarly to the evolutionary history of animals. It’s a little less exact due to the changeable nature of making food, but history and relationships can be seen. I claim that the filled shape with sealed edges that is shared by ravioli, pop tarts, and Uncrustables sandwiches is an analogous structure, and grouping all three into one genus is not supported by their evolutionary history. (How is this a stronger thesis than most of what I wrote in college?)
Before we get bogged down in the details, let’s start with an overview of the big picture. Do we organize food by the culture that created it, or by its components, or by its style? If we were comparing something like sushi to something like ceviche, cultural differences would definitely come into play. However all three of the food families in question (pocket pies, sandwiches, and Italian pasta) are Western European or American in origin with heavy naturalization in white American culinary culture. Thus, we can mostly ignore cultural differences and focus on the structure.
There’s not a single common ancestor to ALL food like there is in animals, but with some grouping we can get to plant-based at the kingdom level, grain-based at the phylum level, flour-based at the class level, and divide that into the subclasses of Savory and Sweet.
Each of these two subclasses branches off into many, many infraclasses and orders. The three we are most interested in I postulate are as follows:
Putting the pie in an entirely sweet subclass, I realize, is not entirely in keeping with history as meat pies were and are rather common. If I cared enough to edit all of my diagrams at this point I would go back and do so, but this is a Tumblr essay that will maybe be fully read by a dozen people so I will call it fine. Either way, pie is the common ancestor to which we trace the pop-tart.
As you can see, each of the parties in question (Pop-tarts, ravioli, and Uncrustables) have an easily tracked evolutionary line and their filled wheat-flour-based shapes are analogous structures, not shared by a common ancestor.
Finally, to conclude my point, close relatives of the species in question can also help determine if they are related. If the close relatives of both species share the same traits, then they can be more seriously studied for relatedness. Let’s look at the closest relatives of ravioli (other members of the fresh pasta family), uncrustables (other members of the Sandwich family), and pop tarts (other members of the Pie family).
Even the closest relatives often do not share the filled form, so saying that poptarts and uncrustables ARE ravioli ignores culinary history as well as common sense.
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