[Question] Reference request: human as “backup”

I re­mem­ber read­ing some pa­per that sug­gests hu­mans to take a spe­cial­ized role in­side su­per AI, like mi­to­chon­dria, or like a biolog­i­cal “backup”. The ar­gu­ment was that hu­mans might have spe­cial­ized func­tions that they can do well, like mi­to­chon­dria is good at mak­ing en­ergy. And hu­mans might be good at sur­viv­ing, so might be a good “biolog­i­cal backup”.

I feel like it’s by Ver­nor Vinge, but I just checked and he didn’t write that. I googled around and couldn’t find it ei­ther. Can you find from which pa­per this might have come from?