Traditional practice in some groups of Australian indigenous people had it that a male wasn't adult unless he'd had his upper incisors "evulsed", ie knocked out, as part of his rite of passage from childhood. More visible, perhaps than circumcision or subincision, which was also practised. You weren't acceptable (read "beautiful") without the gap.

On the original topic, Rutherford (the one instrumental in the development of atomic theory) once, famously, told one of his postgrad students
"If you can't explain your research to the cleaning lady you don't understand it yourself."

I've always regarded the story as a canard on cleaning ladies.

As it happens, in post-WWII Oz we got lots of "Displaced Persons" from Europe and other refugees among our immigrants. Many were extremely well qualified in various fields but their qualifications were routinely dismissed unless they came from Oxbridge; none of them was called Werner von Braun. More than once, the story around physics departments was that a postgrad would be tearing their hair out trying to solve some intractable problem in the wee small hours and would be given a suggestion by the cleaner; the postgrad's supervisor would be informed about the suggestion, respond that it was "Brilliant" and ask how the student thought of it, to be told the cleaner had suggested it. Subsequent interview of the cleaner would reveal that he (occasionally "she") had been a leader in the field, pre War, in some Eastern European university.

Now apocryphal, the story was probably true in one occasion and I've used it (and the Lord Rutherford one) routinely as reminders to students and academics alike.

And I think I can refute any accusation of racism made by the uninformed, and even those made by the informed.

Cheers, Rowan