When the continents were defined, the distinction was as much cultural as geographical even then. That's why the ancients knew of three continents even though the three they knew are physically attached to one another to the point that there is the greatest debate about two of them.
"Now everyone was giving her that kind of look UFOlogists get when they suddenly say, 'Hey, if you shade your eyes you can see it is just a flock of geese after all.'"
"You can't erase icing."
"I can't believe it doesn't work! I found it on the internet, man!"