[dredmorbius]

Symbiogenesis of mitochondria substantially pre-dates the 2000s. It was first proposed over a century ago, 1905 and 1910 by Russian botanist Konstantin Mereschkowski, and substantiated with evidence by Lynn Margulis (a very substantial evolutionary biologist, also one of Carl Sagan's wives) in 1967.

<https://en.wikipedia.org/wiki/Symbiogenesis>

Mitochondria were sufficiently established in general awareness to be a plot point of Madeleine L'Engle's A Wrinkle in Time, being a concept which fascinated the character of Charles Wallace Murray, a young prodigy, in the stories. Though I don't recall if symbiogenesis is specifically referenced. The first story in the series was published in 1962.

[heyoni]

Sure but when it was taught in the 2000’s, it was always done with a big caveat about how the theory was still being debated. In hindsight, all previous mentions will seem like substantiated and obvious statements but there’s a reason articles about it are still coming out today.

[dredmorbius]

I'm not an area expert, and of course don't know what you were taught, or even what general pedagogy over recent decades has been.

I suspect that strong confirmatory evidence came through awareness and analysis of mitochondrial DNA, a term which begins apppearing in Google Ngrams as of the 1960s. Full DNA analysis likely wouldn't have occurred until the 1990s or early aughts, when full genome sequencing became available, so the point might have been argued until then. It strikes me as a rather rear-guard objection at that point however.

(I'd tried a few times to make a clearer assessment of when the view became mainstream, with inconclusive results, though "proposed in the early 20th century, largely substantiated in the 1960s, and all but sealed by 2000" seems a fair statement.)

[kuhewa]

We don't teach theories in primary and secondary education when they are first proposed though. And don't come at me with the Wikipedia summary intro paragraph sir — Margulis started promoting the idea in 1967 with a theory paper, she didn't substantiate it with new evidence. It required the genetic evidence later decades would bring to really substantiate.

And yes, no one has questioned the existence of mitochondria for a good long while now.