How many of you learned in school that the living world is divided into two kingdoms, the plants and animals? Or three, plants, animals, and protists? I did.
Well, you may be suprised to learn that the first scheme was antiquated by 1866, and the second by 1956? Here's the current six-kingdom list, from Wikipedia:
Eubacteria, Archaebacteria, Protista, Fungi, Plantae, Animalia.
Or how about basic tastes? Four? (Salty, sour, bitter, sweet.) That's what I was taught in the sixties and seventies. Well the fifth basic taste has been known since 1908.
Why does it take a century or so for these things to get into textbooks?