As Megan is telling Cueball, separate species of animals have evolved into "crab-like" forms at different times. Naturalists who noticed the tendency gave it the name carcinization.
It is a specific form of convergent evolution, where differing families of animals (in this case, nominally across the crustacea) develop a tendency towards developing a 'crab' bodyplan to a greater degree than their origins would suggest. A similar process has created several varieties of river dolphin with similar adaptations to their environments, despite being 'stranded' offshoots of different forerunner pelagic species.
"True crabs" (Brachyura) form just a small subset of the Crustacea subphylum, and the Cancer genus is a subset of that, yet there appears to be something about the bodyplan and even resulting behaviour that has meant a number of species have arisen from alternate areas of the family tree that are now trivially indistinguishable without extensive study.
Carl Linnaeus even initially included all Crustacea under the 'Cancer' genus (using the Latin name for crabs), and his taxonomic classification has been heavily refined as further knowledge has come to light, in order to reveal this phenomenon.
Apparently this principle is much stronger in the webcomic than in real life, as shortly after being told this, Megan notices that Cueball (not a crustacean!) has himself turned into a crab. This isn't really evolution as we know it (outside Pokémon evolution at least), which refers to changes (usually gradual changes, but not always) in a species across generations caused by random mutations. The organisms individually never change, they are merely different from their ancestors, and the organisms with changes that make them more fit for their environment are the ones who are more likely to survive long enough to pass down those changes. What happens to Cueball is more like a transformation, but it could still be called 'carcinization', since he becomes crab-like. The comic strip might be an allusion to Franz Kafka's short story The Metamorphosis (another word used to describe life-forms that dramatically transform themselves, like caterpillars turning into butterflies), which starts with the main character suddenly waking up and finding that he has transformed into a giant bug.
Cueball's sudden transformation is perhaps explained by the title text, that "Nature abhors a vacuum and anything that's not a crab". The text is a reference to Aristotle's Horror vacui, a statement about how empty space tends to be immediately refilled by surrounding things, so vacuums seem to be impossible to maintain. As does "not being a crab", it seems.
Strictly speaking, we don't know for certain that Cueball actually transformed; it could be that he has ducked out of sight and left a crab in his place (or noticed a crab conveniently nearby) to play a prank on Megan.
- [Cueball and Megan are walking next to each other towards the left with Megan looking back at Cueball.]
- Megan: Have you heard of "carcinization"?
- Megan: The tendency of nature to evolve things into crabs.
- Cueball: Oh?
- [They continue to walk, both of them looking forward.]
- Megan: Yeah, the basic "crab" design has evolved separately a number of times.
- Cueball: Evolution just loves making crabs, I guess!
- [Narrower panel with only Megan seen walking on while lifting both her arms slightly to each side.]
- Megan: Apparently!
- [Two smaller beat panels are drawn between the previous and next normal sized panels. The first is a bit lower than the top of the normal panels, and is partly lying in over the other small panel, which is below and to the right of the first. The top panel shows Megan continuing to walk along. The second shows Megan stopping and turning to look back.]
- [Megan has turned completely and is looking down at a small crab scuttling along on the ground where Cueball was before.]
- Megan: Oh no
In January 2020, less than half a year before this comic was released, the Dinosaur Comic also released a comic about Carcinization. This web comic is on Randall's list of Comics I enjoy and was also used in 145: Parody Week: Dinosaur Comics. Another popular webcomic, Questionable Content, had a crab-themed comic the day before this comic was released.
Just a month after the release of this comic, "carcinization" was the Word of the Day in Wiktionary.
This comic was also the inspiration for SCP-6010, a story about all animal life turning into crabs, set in the SCP Foundation setting. SCP 6010 mentions life turning into crabs o June 1st 2019, the release date for this comic.
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Honestly, what is there to explain here? The only thing I can imagine in this explanation page is an explanation of why carcinization happens, which isn't explaining the comic. 22.214.171.124 22:52, 1 June 2020 (UTC)
- We might need to look at the differences between various 'false crabs' and their relatives, to show that in the false crabs' lifestyle, some crab-feature they have and their close cousinshttps://www.explainxkcd.com/wiki/index.php?title=User:Lightcaller&action=edit&redlink=1 do not is a thing that the CCs would be unable to match if they lived in the FC-like style. This is probably the subject of a whole dissertation (if not several). 126.96.36.199 00:22, 2 June 2020 (UTC)
Does this mean all programming languages evolve into Rust?188.8.131.52 23:08, 1 June 2020 (UTC)
- I think this might be part of the joke here. Rust has partially replaced other programming languages in well known companies, and it has been the most beloved language for four years straight (according to StackOverflow survey). There has been many XKCDs with programming themes, I don't think Rust would go unnoticed for so long. (Note: Rust's mascot is a crab) 184.108.40.206 15:22, 2 June 2020 (UTC)
Is it just a coincidence that today's Questionable Content also contained a reference to crabs? 220.127.116.11 00:31, 2 June 2020 (UTC)
It may be of note that Qwantz (a comic previously parodied in 145) did a comic about carcinisation earlier this year 18.104.22.168 01:08, 2 June 2020 (UTC)
- Why do you call Dinosaur Comic Qwantz? --Kynde (talk) 11:51, 2 June 2020 (UTC) <-- because that's the web URLCellocgw (talk) 12:36, 2 June 2020 (UTC)
Gotta say, this is the first xkcd in a while that made me laugh. Lightcaller (talk) 03:49, 2 June 2020 (UTC)
Nature: Time for crab 22.214.171.124 04:58, 2 June 2020 (UTC)
This comic was posted 3 weeks too early, seeing as Cancer doesn't start until June 21 or 22 Cellocgw (talk) 12:34, 2 June 2020 (UTC)
Looks like it already happened at one Taiwanese semiconductor company: https://en.wikipedia.org/wiki/File:Realtek_logo_vector.svg. Shamino (talk) 14:11, 2 June 2020 (UTC)
The word "evolution" predates Darwin by at least a hundred years. It means a gradual development. Darwinian descent with modification is a specific type of evolution but the term can and is used other forms of gradual development, without any implication that anything Darwinian is going on.126.96.36.199 10:08, 4 June 2020 (UTC)
- This is a typical confusion of means vs ends. Evolution is a description of the results - the ends. Darwin described natural selection - a means capable of producing those ends that works well with observed data. There were, and still are theories that describe other means, which fit observations to differing degrees. Shamino (talk) 12:56, 4 June 2020 (UTC)
IMHO, it's pretty likely the last panel is a reference to webcomic name - the formatting of "OH NO" with no punctuation, no other text, the fact it's the last panel etc all seem not particularly xkcd-ish, and very webcomic name-ish. Do we really need this disclaimer " But may have nothing to do with it, since having told Cueball about this and then seeing him turned into a crab, may indicate Megan was the cause! And either way, saying "oh no" to something bad is not particular to the mentioned web comic." Stevage (talk) 13:53, 2 June 2020 (UTC)
- Agreed, the rambling is not needed. Good edit. --V2Blast (talk) 19:05, 2 June 2020 (UTC)
- I disagree that this is related to "webcomic name". "Oh no" doesn't necessarily relate to anything. It is unclear whether Randall is aware of or a fan of that comic. 188.8.131.52 21:57, 2 June 2020 (UTC)
- I removed it. It's not even lowercase. 184.108.40.206 23:59, 2 June 2020 (UTC)
- By weird coincidence yesterdays Questionable Content ended with Ancient Aliens were Crabs gag...
Not sure if that's relevant, but it's at least interesting. --220.127.116.11 22:39, 2 June 2020 (UTC)
There is a clear parallel with Ionesco's Rhinoceros, even the term Rhinocerisation.
18.104.22.168 20:02, 4 June 2020 (UTC)
Am I the only one who every time he sees this comic constantly thinks of the spooky South Park song "Crab People, Crab People. Look like crabs. Talk like people"? Gunterkoenigsmann (talk) 17:17, 5 June 2020 (UTC)
I wonder if this comic might also be a reference to Karcrab, a meme about Karkat. Karkat is a character in Homestuck, which is also on Randall's list of favorite comics. Karkat is generally a very angry (and therefore crabby) alien. He wields a sickle that looks like a crab claw, and he has a lusus (basically an animal-like alien that acts like a parent) that is a crab. Since he's an alien, his crab-like attributes would lend support to the idea that crabs tend to evolve even on alien planets. Coincidence? - PsuedoBubble (talk) 02:06, 31 July 2020 (UTC)