Sourdough Starter
Sourdough Starter
[Cueball stands in front of a kitchen counter looking down at a glass jar he is holding in both hands. The jar's flat lid is lying on the table. There is another large jar farther back on the counter with a lid, with a small handle, on. In both jars there is a substance, which do stay in the same position in the jar even though Cueball tilts the jar he is holding.] Cueball: My sourdough starter is coming along nicely!
[Caption below the panel] Theory: The coronavirus is a yeast symbiont with an extremely convoluted parasitic life cycle.

This comic is another comic in a series of comics related to the COVID-19 pandemic .
Recently, because of the coronavirus, many people are forced to stay home in quarantine or under Stay-at-home orders . These conditions often lead to spare time that needs to be filled, and many people have turned to baking, which can usually be done entirely at home, is relatively time-consuming, and has the advantage of producing finished food, lessening the need to go out to buy food. This trend is common enough that baking supplies, including yeast, have seen a spike in demand, to the point where many people have trouble finding it.
As an alternative to yeast, consumers can grow their own sourdough starter, which is a symbiotic culture of yeast and bacteria naturally found in flour. Once the starter has matured, part of it can be used to make bread or other baked good rise, while the remainder can be mixed with more water and nutrients to allow the remaining yeast and bacteria to multiply once again. Because these populations need to be maintained, it's often been a practice to trade starters from house to house, with each home using starter when they need it, then setting up the remaining starter to breed more. This has historically been a social activity, allowing people who share an interest in baking to meet, share recipes, and spend time together.
The upshot of all of this is that the coronavirus pandemic has created conditions in which yeast (and symbiotic bacteria) are being bred in larger numbers, both by companies trying to fill demand, and by individuals trying to make their own. The joke is that this outcome is, in fact, the entire purpose of the coronavirus, which is in a symbiotic relationship with yeast. The entire global pandemic, by this logic, is directed to keep humans indoors and baking so that more yeast (and bacteria) is bred. The practice of swapping sourdough starters means that they're propagated more widely, increasing and distributing the yeast population (while potentially giving the virus more opportunity to spread, as people socialize).
As Randall points out, this cycle is extremely convoluted.  However, it is not unknown for parasites to drive the responses of other creatures in order to propagate themselves. For example, Toxoplasma gondii infects mice, but can only reproduce when it infects cats.  The organism has therefore adapted to infect the nervous systems of mice, making them extremely reckless, increasing their odds of being caught and eaten by cats, allowing the the parasite to move to a new host.  Some flatworm parasites have very complex life cycles that involve four different host animals .
Randall has previously speculated about unusual parasitic organisms in 2246: Christmas Presents , in which he "concluded" that Christmas presents are parasites of Christmas trees, possibly mediated by a fungus. And in 1664: Mycology a fungus infects human brains making them wish to study (and thus grow more of) this fungus.
Viruses are not organisms (lacking some of the defining features of life), and it is debatable whether they would be considered parasites. Moreover, this theory is obviously implausible for a number of reasons.  The most obvious being that natural responses, particularly of viruses and simple organisms, evolve over a long time scale.  SARS-CoV-2, the virus responsible for the current pandemic, has very likely been infecting humans for less than one year, certainly not long enough to evolve such a complex set of behaviors. At the same time, a symbiotic relationship would require yeast to somehow contribute to the life cycle of the coronavirus in a meaningful way, which is unlikely when the yeast is being artificially bred in isolated containers.  If however, as suggested by the title text, people getting together to swap yeast starters after the lockdown ends does cause the virus to begin spreading in humans again as a result of the social contact, then the yeast would be contributing to the life cycle of the coronavirus, in an equally convoluted way.  The humor, therefore, is derived from the fact that this is a comical exaggeration, but based on cycles that actually do happen in nature.
[Cueball stands in front of a kitchen counter looking down at a glass jar he is holding in both hands. The jar's flat lid is lying on the table. There is another large jar farther back on the counter with a lid, with a small handle, on. In both jars there is a substance, which do stay in the same position in the jar even though Cueball tilts the jar he is holding.] Cueball: My sourdough starter is coming along nicely!
[Caption below the panel] Theory: The coronavirus is a yeast symbiont with an extremely convoluted parasitic life cycle.
