The Spanish brought the potatoe to Europe from South and Central America (Inca, Maya, Aztec, Toltec, ...)
But they didn't really know why those ppl cultivated it. They planted it here and like you said they first served the green "nobs", the flowers grow out of (not the fruits <img src="/ubbthreads/images/graemlins/winkwink.gif" alt="" />). They didn't knew it was all about the roots.
Same thing more or less with another "fruit/vegie" that was brought to Europe by conquistadores. Peanuts. <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
