Linguist: Three of the four subfamilies of the so-called "Austronesian" languages are found only among indigenous peoples in Taiwan, whereas the fourth is found on islands over a huge area stretching from Madagascar to the eastern Pacific Ocean.
Conclusion (hence)
Austronesia-speaking people originated in Taiwan and later migrated to other islands.
Intermediate Conclusion (these facts suggest)
Taiwan in the homeland where Austronesian languages have been spoken longest.
Evidence
All subfamilies of Austronesian originated in the same language, which would have been in a single geographic location.
3 of the 4 subfamilies are found only in Taiwan, whereas the fourth is found on islands stretching from Madagascar to the eastern Pacific.
Evaluate
On Main Conclusion questions, the conclusion is almost always earlier than the evidence, but not this time.
The last sentence offers four consecutive claims, and the keywords go like this ...
Since claim 1, which means claim 2, these facts suggest that claim 3 and hence, that claim 4.
So we can see that 1 -> 2 -> 3 -> 4.
The first sentence is a fact, not an opinion, so it couldn't be the Main Conclusion.
Goal
Let's look for a rephrasing of the final claim, .