1490 wrote...
Ah...you're probably right. I remember her saying they developed with microorganisms in a different fashion than we did and that's why their immune systems were already weak: they didn't need them to be strong on the planet. Their cohabitating bacteria must be completely unable to affect them in negative ways or something. Just like cholorplasts in plant that absorb light are evolved from light-utilizing cyanobacteria that primitive plant cells ingested hundreds of millions of years ago.
Finally caught up whew.
Quarians have zero insects on their homeworld. None. Zilch. Every single plant evolved to have the mammals carry their pollen/spores for distribution. In time the mammals evolved to accept them as beneficial and their immune systems evolved around carrying foreign matter.
Jump to now and you have a Specie that acts as a sponge in any enviroment they enter. Absorbing and processing everything it comes into contact with.
Without the plantlife of their worlds their immune systems cannot develop at all because they are meant to only react with those key fauna which provide beneficial side effects. The human system in comparison automatically repels such invaders (hair in your nose/ears, sneezing) while the Quarian one takes them all in.
A Quarian having grown on their homeworld would be able to travel around without a suit for most nominally clean enviroments in the rest of the galaxy, their system has by now adapted and learned what foreign particles it can use and simply kicks the non essential ones out as unusable.
A space born Quarian has had no such adaption.
That's my Layman's theory right now. <3