Cicadas are a species of insect whose nymphs burrow underground and emerge as adults to reproduce several years later. One common species in North America is the 17-year cicada, also known as the periodical cicada. These cicadas form distinct broods which burrow and emerge as a group every 17 years, with different broods starting the cycle at different times. This results in a couple of weeks every 17 years when the cicadas swarm in huge numbers, then vanish just as quickly when the adults die off. Cicadas also make a distinctive buzzing sound, which makes their periodic appearance even more memorable.
In the comic, Cueball and Ponytail have accidentally created 17-second cicadas using genetic engineering. This means that rather than seeing a massive swarm every 17 years, they have to deal with a swarm every 17 seconds. This makes it very difficult for them to do their work, especially to figure out how the cicadas were created, because the swarm keeps interrupting their work. Note that the comic has been drawn differently than most other straight four panel comics, probably to highlight the interruptions of the buzzing swarm - see the Transcript.
The title text is a pun on "circadian rhythm." In particular, it might resemble something said to someone getting adjusted to a new sleep schedule. But here it is the 17 seconds interruption, not a time zone shift, that has to be adjusted for.
This entire comic seems to only have been a lead-up to the "cicadian rhythm" punchline. This is an interesting suggestion since Randall has mentioned in an interview that he makes up the title text after completing the comic. Seems like he made an exception here; unless he didn't.
- [This comic is laid out in a variation of a regular four-panel comic. One wide panel is overlaid by two smaller panels, which are placed where the second and fourth panels would be. These panels are slightly offset so they extend above the wide panel.]
- [Cueball and Ponytail are facing each other across a desk while having a conversation. Cueball is holding up a tablet in his hand while Ponytail is typing at a laptop on the desk.]
- Cueball: What can you tell from genome comparison?
- Ponytail: I think there's a duplication on the -
- Ponytail: Look out!
- [An overlaid panel shows that the air is full of flying cicadas, many of which have landed on Cueball, Ponytail, the laptop, the tablet, and the desk. Ponytail and Cueball have their arms up in a futile attempt to shield themselves from the bugs, with Cueball having put the tablet down on the table.]
- [The cicadas are gone, and Cueball and Ponytail resume their conversation. Cueball has picked up the tablet again]
- Ponytail: - a duplication on the gene right before the cleavage site, so the resulting protein -
- Ponytail: Look out!
- [An overlaid panel shows that the air is again full of flying cicadas, which have once again landed on Cueball, Ponytail, the laptop, the tablet, and the desk. Ponytail and Cueball have raised their arms to shield themselves again.]
- [Caption below the large panel:]
- Our genetics work has produced 17-second cicadas, but we're having a hard time figuring out how.
The widely-accepted scientific explanation for the long and seemingly arbitrary 17-year lifecycle is that seventeen is a prime number - it's believed that this is an evolutionary adaptation against lifecycles of competitors taking easy advantage of the cicada as a foodsource (if a predator) or emerging early to dominating their shared foodsource (if a fellow feeder), since 17 years cannot be divided by any whole number of years other than itself and 1.
A 16-year cicada might find a creature with an 8-year, 4-year or biennial cycle could profit from it in a 'clash' of expectations, but only a cycle that is a multiple of 17 (by an identical accident of evolution, that must also match the 'beat' years of the Cicada to be useful) would affect the presumed ancestors of the comic-strip breed. Predators often work to yearly cycles of plenty and scarcity of food, or can survive a low number of famine years between the better ones, but if they have less than one year of 'bounty' for every decade or so of 'normal' feeding then they cannot build up the numbers needed to threaten such prey that plays the long-game.
Other broods of cicada have 13-year lifecycles (the next lowest prime number), and would potentially clash for resources (or hybridise) only every 221 years. Even if this causes a single bad cycle, for both sub-species, the next cycle of appearance is their own once more (for each) and the respective populations have plenty of opportunity to recover from this event by the time a further two centuries pass. Thus (it is theorised!) the happenstance evolution of a period of dormancy that gives a cycle of a significantly large prime-number of years - though still low enough to survive that period - is ultimately more advantageous than any cousins who tried to evolve to a period with smaller factors/shorter harmonics.
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Okay, now that title text is an exceptional pun. Also, First. —Kazvorpal (talk) 22:51, 3 February 2020 (UTC)
- 1258: First and 269: TCMP to you too. ;-) --Kynde (talk) 13:01, 4 February 2020 (UTC)
I just realized that there is a pun in every punchline, which I find oddly pleasing in this specific context. 126.96.36.199 23:48, 3 February 2020 (UTC)
Randall said in an interview that he first makes the entire comic and only comes up with the title text shortly before publishing. So either he broke his own rule or the comic is not a buildup to the punch line in the title text. Fabian42 (talk) 08:24, 4 February 2020 (UTC)
- Quite sure he got the title text first this time and found a way to make a comic that fitted it. But we will never know if he doesn't make a new interview. Would really like to see a link to that interview to add it to the explanation. --Kynde (talk) 13:01, 4 February 2020 (UTC)
- Sorry, I only know it from memory, from when I watched about 10 interviews with and talks by him in a day. :D And it was all YouTube recommendations and a few months old, so it's probably not even in my YouTube history anymore. Fabian42 (talk) 22:50, 5 February 2020 (UTC)
I think the current explanation is sufficient and complete - I'd even go so far to remove the part about why there is a 17-year cycle since for the understanding of the comic it's totally irrelevant. Elektrizikekswerk (talk) 10:48, 4 February 2020 (UTC)
- No that is very relevant. It is the reason why 17 seconds was chosen and very likely why Randall thinks these cicadas are so interesting that he ended up doing a comic on them. But I agree with the completeness. --Kynde (talk) 13:01, 4 February 2020 (UTC)
- If it was 12 years instead it would be 12 seconds in the comic. Being prime or not doesn't matter at all neither for the comic nor the explanation. It's trivia at best. Elektrizikekswerk (talk) 14:04, 4 February 2020 (UTC)
- Twelve years wouldn't work for cicadas as it's not prime. 17 (or any other prime number of) seconds won't work either because a second is an arbitrary amount of time. 188.8.131.52 14:28, 4 February 2020 (UTC)
- And still it's not relevant for the comic. Look, I get your point but for the sake of understanding the comic it simply doesn't matter if it was 12, 17, 23 or 53 years. Elektrizikekswerk (talk) 09:05, 5 February 2020 (UTC)
- However, the first question I asked myself when I read the first version of this explanation (without of an explanation of the 17 years), was: why is it 17 years? what weird kind of insect is that? I clicked the wiki link and found out. Therefore it is not necessary to put in here, but very interesting, and I assue finding out about the actual 17 years cicadas is the thing most people need an explanation with. Similar things are done for almost all comics. --Lupo (talk) 09:29, 5 February 2020 (UTC)
- Yeah, that this is done with many other explanations is quite frankly a problem I'm having with those explanations. If some specific knowledge is needed to understand the comic it's fine to include that in the explanation. But if it's not needed to understand then it is to be considered trivia at most. Your question "Why is it 17 years?" leads to the question "What is a prime number?" (I know this is a bad example since it's most likely common knowledge among those who visit this page or XKCD. But what if not?) which may lead to even more basic questions. My point is: Where do you stop? In my opinion a comic's explanation should provide the minimum information needed to explain the comic. Not less but also not more. If you want to know more about a specific "thing" in the comic's explanation just click the link. That's why we provide these links in the first place, isn't it? Elektrizikekswerk (talk) 10:32, 5 February 2020 (UTC)
- I fought the same fight on some comics (e.g. 2207: Math Work, where the explanation became very tangential.) I personally prefer concise explanations as well, but it doesn't appear to be the current style of the explanations. Some seem to think: "More means better." - It's really tough to decide where explaining the comic ends and where "further reading" starts. In this comic the excursion on 17 year lifespans is (currently?) quite short, so I do not see it as problematic. Much "worse" is in my opinion the part guessing about the reason of experimenting with cicadas. --Lupo (talk) 11:24, 5 February 2020 (UTC)
- I agree with Elektrizikekswerk and Lupo. The motivation for the wiki is to explain the comic and possibly help people locate and understand hidden jokes or hints. Non of this requires the information about why the Cicades have a 17 year lifecycle. It is however very interesting and nice to know (I didn't know either) which is in my mind precisely what a trivia section is for. The guessing on why the experiment is performed in the first place is completely unnecessary. In order to understand and appreciate the humour in the comic a simple "because that's what scientists do" would suffice. Bischoff (talk) 11:34, 5 February 2020 (UTC)
- I added the section on prime numbered lifecycles, but I do agree, it is irrelevant to understanding the comic. It's a pretty cool fact, but it is cidada trivia at best. If it breaks the flow of the explanation at present, I'm happy for it to be moved or removed. Hawthorn (talk) 11:40, 5 February 2020 (UTC)
- Since there seems to be consesus I just removed the part about the "why did they do the research" and moved the part about the prime numbers to the trivia section. Elektrizikekswerk (talk) 11:56, 5 February 2020 (UTC)
- I don't know if it's still Trivial enough to be in Trivia, but I expanded it to (best guess, and I think current) thinking on the background to the septendecenial insect. That the actual proposed mechanism/cause for the 17-year natural Cicada cannot really have anything to do with the fictional reason behind their roughly 31556952-times more frequent offspring (unless someone engineered the lab environment to express seasonal pulses in heat, surrogate root bichemistry, etc, at the faster rate to cue the more vastly more responsive experimental subjects) probably means it should stay in Trivia rather than form any kind of Explanation (beyond, as it already does, explaining that the original insect actually exists). Or can be reverted, to leave people wondering what the marvel of God Or Nature it is, until they decide to go and look it up themselves. 184.108.40.206 19:39, 5 February 2020 (UTC)
- (reduced the indenting) The process of evolution is that benefits happen not for any ultimate purpose but are randomly selected by environmental circumstances. If cicadas randomly reproduce on 1 or 2 or 3 or 5 or multiples of those numbers then it is more likely that their predators will be able to match that cycle and it will be less effective. So if the random changes in their maturity cycles happen to hit upon 13 or 17 then it is less likely that the predators will match that cycle. Therefore it becomes a more successful reproductive method and that's how it happens. The prime number is not a reason or cause of the 17 year cycle. It is a consequence that this particular random change in cycle provides (after the fact) a better survival chance than any other cycle. This is an important distinction in understanding evolution. Rtanenbaum (talk) 20:20, 5 February 2020 (UTC)
- (Yeah, sorry, +1 on indent aain.) Indeed, it's difficult to use the right language to get that point across, though. In my Trivia edit I put in the word "happenstance" at one point. An awkward word, but trying to make that point. Ditto demonstrating why 16 years is 'worse' (while mentioning just one reason why, e.g., 282,589,933−1 would be an impractical choice of Prime, too!). So DNA/etc that just happens to produce an effective counter-to-N (of external cues indicating another year has passed) before provoking a given stage of life transition is better when that N is 17 (or 13), and other Ns are less advantageous. They may well have arisen, but died out. (As did the 13-year Brood-21, IIRC, for whatever reason, maybe anthropogenic, at the end of the 19thC.) Not that we're entirely sure why 'better' (I would firmly side with it being likely related to predator and/or resource-competitor avoidance, with self-reinforcing temporal divergence from their relatives that chose a different frequency and/or offset, but there could be other advantages not observed), and the cicadas probably don't know or properly appreciate what they're doing. Their ancestors definitely did not go "Hey, chaps, I've got a brilliant plan...", just before one of their kind decided to make his inaugural multi-year nap. But something happened, and a fascinating emergent behaviour resulted. Don't you just love the Universe, sometimes? 220.127.116.11 22:56, 5 February 2020 (UTC)
- The intendation gets pretty confusing with my reply below for a comment far above. Anyway, are you sure that 2⁸²⁵⁸⁹⁹³³-1 is a prime number? :D I couldn't even get an online "big number calculator" to just print out the number for me, especially not check for being prime. Fabian42 (talk) 23:06, 5 February 2020 (UTC)
- It actually is the Largest known prime number as of January 2020. It was discovered (according to the linked wiki article) in December 2018. --Lupo (talk) 07:40, 6 February 2020 (UTC)
- Why did you make an edit to replace "go so far to remove" with "go so far and remove"? Fabian42 (talk) 18:47, 5 February 2020 (UTC)
- Because I'm a dumb German and "to" just sounds wrong in my head ;) Reverted it again, thanks :) Elektrizikekswerk (talk) 09:13, 6 February 2020 (UTC)
- The correct phrase you want is "go so far as to remove". :) You were missing the word "as". The phrase "go so far as" is very common. NiceGuy1 (talk) 04:27, 16 February 2020 (UTC)
I used to listen to, a lot to R.E.M.'s 'Daysleeper' where they mention 'circadian rhytm' (at the end of the first verse) - that line I always overheard as 'cicadian rhytm' (the 'r' is disappearing)... wonder if this has something to do with the pun too? Or coincidence? 18.104.22.168 13:47, 18 February 2020 (UTC)