Not breathing oxygen is way more toxic, though. That will kill you in a few minutes.
Sure, I imagine off-world lifeforms having entirely different metabolism. Like when we hear “this planet has a methane atmosphere” it’s like holy cow, sounds rough, but alien entities would possibly think the same thing about our planet of water and nitrogen. Imagine how horrible it would sound to someone who was water-soluble. “H2O rains down from the sky!!”
Fun fact: humans aren’t responsible for the first mass extinction caused by organisms polluting the atmosphere with poisonous gas. Blue-green algae did it first, with “a decrease in the size of the biosphere of >80%”.
This reminds me of the Deathworlders series.
Is that the one where humans are consensually employed by all the comparatively more advanced alien species of our galaxy as their warriors or executives because even our weakest human is significantly more powerful to any of the nearest alien due to the nature of us all having been evolved from an ancient ape species that were prone to violence?
https://deathworlders.com/ - Dunno if it goes into that detail of us evolving from violent apes, but at least from chapter zero, seems to be mostly due to us being from a “high gravity” world and having “builtin combat drugs” (adrenalin)
Considering the amount of things that can kill us, both micro and macro, and the fact that we ingest poison (alcohol, drugs and even actual frog poison) for fun, it’s pretty easy for any alien life to look at us and think “holy shit, those creatures are fucking hardcore!”
Plănts: We will make our own food and output a poisonous gas, that way nobody will bother us.
Animals: Allow us to introduce ourselves.
Pretty sure there’s some worms or something that live by deep sea vents which breathe sulfur not oxygen and are believed to live forever because of this.
There’s a bunch of creatures that don’t use oxygen but they’re mostly all prokaryotes, since oxygen metabolism unlocks a shitload of energy you can use for being large and complex.
