cunning linguists

i'm still reading that damned Diamond book.
yes, the same one i bought in the Seatac airport to accompany me throughout my Alaska trip.

but i'd like to just talk about a random fact.
it's about Eastern Asia.

The majority of eastern Asians speak some form of Sino-Tibetan, which includes Mandarin, Cantonese, and all those dialect/languages that we lump together as "Chinese".
this extends out of China and into most of Myanmar.

There is another language that is spottily represented around southern China and extends into northern Vietnam, Laos, and Thailand. it's called the Miao-Yao language group and is probably very spotty because of the infiltration and overbearing qualities of the "modernized" Chinese over these people who might be compared to Native Americans in the fact that their land has been somewhat overrun by outside forces. so the forced change in language, or conquering of the people of the Miao-Yao languages, left the language with only small island strongholds.

Then there's another language group called Tai-Kadai, which encompasses some of southern China, some of eastern Myanmar, most of Thailand, and most of Laos.
historical writings recorded that the language started in southern China and had people migrate south to where the language is more prevalent today.

Finally there's Austroasiatic which can be found in most of Vietnam, Cambodia and western Malaysia. There are also large chunks of this language group in eastern India, and another near Bombay in the west.
what Diamond might allude to, but isn't obvious in the chapter where he explores these languages is that this austroasiatic language group extends through most of Indonesia and into Polynesia. It also can be found as far away as northern Madagascar.

so there are two things i wanted to say here.
1) i should have learned more about the vietnam war than i did, but was there some sort of Laotian/Vietnamese rivalry that may be explained by language differences?

2) that austroasiatic culture is crazy. i think they start to show up in the archaeological record around 3200 BP and break through areas that hadn't been explored prior to them. other than australia, the furthest extent people had gone over their entire existence was the Bismarck archipelago, which is that island grouping just beyond Papua New Guinea.

i guess my question is, what the hell would force these people to expand so greatly as to expound exponentially on their seafairing technology. Agriculture had already been in or around that area for 4 thousand years prior to their expansion. so a population boom from that might not explain it.
maybe they were feeling some sort of external influence to explore. China to the north was coming down on them?
do people really wish to explore that much just to see what's out there?
i guess once the technology was set and in constant use, then it wouldn't be as frightful,
but that initial leap...
what urged that?
famine/drought?
war/impending opression?

i guess we could also look to the Minoan of the mediterranean to see what their deal was.
but i know even less about them than i do the Lapita (which is the name of the cultural expansion who allegedly used the one form or another of the austroasiatic languages).

i wonder if digging can ever answer that question...