2161: An Apple a Day

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An Apple a Day
Even the powerful, tart Granny Smith cultivar is proving ineffective against new Gran-negative doctors.
Title text: Even the powerful, tart Granny Smith cultivar is proving ineffective against new Gran-negative doctors.


"An apple a day keeps the doctor away" is a common English proverb and rhyme. The suggestion is that eating one apple daily will keep you healthy, and therefore reduce your necessity to go to the doctor or, more literally, to have the doctor come to you as was likely the case when this proverb was first used.

Megan is giving a talk, starting with the common proverb, before continuing with "At least, it used to." In a normal scenario, this might have been to imply that eating apples is no longer enough to stay healthy. However, in this comic, this expression is reinterpreted to mean that an apple used to repel a doctor. It also suggests that keeping doctors away is of great importance, presumably because doctors in this scenario are undesirable. The method of action of apples is not specified; they could act as repellents, analogous to insect repellent, or possibly as lethal agents, as antibiotics are to bacteria, or fungicides are to fungi.

Megan continues with her reinterpretation, mentioning that doctors have become resistant to apples so two or even three may be needed. As control agents become more widely used, organisms which are less sensitive to the control may become more common, as is happening with mosquitoes becoming insensitive to repellents, or antimicrobial resistance, and pesticide resistance. Such resistant organisms may require higher doses, or use of multiple control agents.

In the worst cases, doctors have become completely immune to apples (i.e., superbugs). A poster behind Megan shows Doctor Ponytail with three apples above her. Megan advocates using the 'finest' apples only in these cases (a reference to multidrug-resistant pathogens, where some antibiotics are only used as a last-resort to reduce the development of resistance to them).

This comic is a clear reference to the overuse of antibiotics in modern society, leading to an increase in antimicrobial resistance ("Superbugs"), which has seen increasing awareness in the last few years. The World Health Organization had the first Antibiotic Awareness Week in 2015, where a talk similar to the one in the comic would seem appropriate. Similar problems occur in growing plants, where various pests (whether insect, fungi, microbes, or plants) adapt to control measures, making control less effective.

In the title text, this is taken further: "Gran-negative" is a pun on Gram-negative, a category of bacteria. A well-known technique called Gram staining distinguishes two classes of bacteria (Gram positive versus Gram negative) on the basis of properties of their cell walls. In this case, Granny Smith apples are supposedly effective against Gran-positive doctors (since the name begins with "Gran"), making them ineffective against new Gran-negative doctors.

Honeycrisp and Granny Smith are two different cultivars of apples. Granny Smith apples are a refreshingly tart green apple, which have mixed reviews among apple eaters; they are used primarily for cooked dishes, rather than eating raw. Conversely, Honeycrisp are a very sweet apple, considered by some to be "an ideal apple for eating raw", and is the state fruit of Minnesota.


[Megan is facing straight out of a slim panel as she stands behind a lectern addressing the reader.]
Megan: An apple a day keeps the doctor away.
Megan: Or at least, it used to.
[The comic zooms out revealing that Megan and the lectern are standing on a podium. Megan is pointing behind her, with a stick, to at a poster prominently featuring Doctor Ponytail with three apples over her head.]
Megan: Over time, some doctors have developed a resistance to apples. Keeping them away takes two or three apples instead of one.
Megan: And there are worrying signs that a few doctors may have become completely immune.
[The comic zooms in again on Megan behind the lectern.]
Megan: So we must stockpile our finest apples in reserve, using them to fend off only the very worst doctors.
Megan: Honeycrisps still work on most of them, but we don't know for how long.

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I get that I shouldn't, but after the first sentence in the second paragrsph, I really wanted to say: "For example, if an opponent controls a thief of sanity and you have a sharktocrab, you may adapt the sharktocrab to tap down the thief." (This is a Magic: The Gathering reference.) 18:05, 10 June 2019 (UTC)

The title text contains a subtle pun with Gran-negative, where the bacterial term is Gram-negative, but instead is referring to Granny-Smith apples - hence, gran-negative. Ianrbibtitlht (talk) 18:06, 10 June 2019 (UTC)

And this is why I come to explainxkcd even when I think I have understood the comic! Thanks! 18:22, 10 June 2019 (UTC)

I felt parts of the explanation were worded a bit clunkily. I'm not strongly attached to my edit, so if others disagree, feel free to revert ;-) -- //gir.st/ (talk) 19:10, 10 June 2019 (U

I feel I must take issue with the statement in the explanation that Granny Smith Apples are 'sour' and agree with the title text that they are 'tart' or possibly 'sharp'. RIIW - Ponder it (talk) 21:21, 10 June 2019 (UTC)

I've found that one apple a day will keep the doctor away, providing you can throw it hard enough and accurately enough at him. RAGBRAIvet (talk) 01:41, 11 June 2019 (UTC). Or her...

Antibiotics weren't my first thought on reading this comic, but rather mosquitoes, which have an amazing tendency to overcome everything we throw at them. There was an article a day or two ago about introducing spider venom into fungus to try a new approach against them. I'm sure there are other examples that occur to others, as resistance increase is a common enough concept. Like many xkcd, it works on multiple levels. Daemonik (talk) 08:58, 11 June 2019 (UTC)

In looking for that, I found interesting item about how some mosquitos are insensitive to DEET (added to explanation). Thanks for the pointer. 19:58, 11 June 2019 (UTC)

We could put our apples on a messaging site that posts to an uncensorable blockchain like https://memo.sv/ so that everybody can reuse others on doctors that haven't seen them yet. What do you think? I was also thinking if a strong AI were developed, it could build new apples as needed. Maybe an AI could be made rapidly by having it learn to predict its own behavior from its code. But you wouldn't want it to accidentally take over the world, so it could have a primary task of being interviewed in an empathic way, answering for example, "are you happy with how fulfilled your need to nurture and empower life is?" Answering this question in depth might stimulate it to understand these concepts, and the response would give the interviewer lots of avenues to understand and verify it further. By the way, there's a 30-page booklet on a technique used to resolve wars rapidly here. 02:08, 11 June 2019 (UTC)

J Milstein (talk) 13:01, 11 June 2019 (UTC) Apples keeping doctors away seems analogous to garlic keeping vampires away J Milstein (talk) 13:01, 11 June 2019 (UTC)

If apples are to garlic as doctors are to vampires, comparing apples and oranges is like comparing doctors to whom?
Holistic Medicine Practitioners? Could be mistaken for similar but quite different? :) (Level of validity makes this comparison questionable, though...) NiceGuy1 (talk) 03:21, 15 June 2019 (UTC)
Also, if apples means stairs, what does garlic mean? Kventin (talk) 07:18, 12 June 2019 (UTC)

Think of the children! https://www.youtube.com/watch?v=QAo5AQF2OVg 01:57, 13 June 2019 (UTC)