Boats

I just had another idea (oh no, not again!).
If we need a major invention to account for the sudden spread of
IE, and agriculture doesn't quite fit the bill, how about the
invention of boats? Suuddenly you can trade, and need a trade
language. First a pidgin and then creole version of your language
spreads along the coasts, with an uncomplicated grammar (Hittite),
later armies with kings, poets, grammarians and other sycophants
follow the trade, with complicated versions of the same language (now
we also know why New Guinea speaks Tok Pisin, and Australia proper
(sort of) English.

Torsten