Title text:
Under the two-domain system, anyone who punches you is technically an Archaean pathogen.
Transcript:
[Cueball, Megan, and White Hat are standing in a lab in front of a root-like phylogeny diagram, looking at it. Behind them is a desk with a microscope on it. There is a pile of items behind it and one item in front. From the plate on the microscope where the sample is, there is a star burst and a line going up to the text said by the sample.]
Cueball: It's weird how, despite being one of the main branches of the tree of life, no Archaea species are known to cause disease in humans.
Megan: Personally, I think it's because those gross methane breathers are too weird and incompetent to figure out how to hurt us even if they wanted to.
Archaea sample: Hey![Caption below the panel:]
Bad news: After overhearing a conversation in our lab, Archaea has finally started harming humans.
Source: https://xkcd.com/3095/
I asked my professor about this. He said there are hypotheses, but no conclusion. The most likely explanation , he said, might have something to do with archaea being closer to us than bacteria in the evolutionary tree.
But there are eukayotic parasites. They are even closer to us. This on its own is not an explanation.