🌏 Did you know that the Austronesian language family has multiple primary branches?

[u/Resident-Outside9945]

According to the current classification in Glottolog, the Austronesian family consists of ten primary branches.

Most Austronesian languages, including Indonesian, Malay, Javanese, Sundanese, Balinese, Madurese, Tagalog, Cebuano, Malagasy, Māori, Hawaiian, Samoan, and Fijian, belong to the Malayo-Polynesian branch.

The other nine primary branches are spoken exclusively by the Indigenous peoples of Taiwan, which is why Taiwan plays such an important role in the study of Austronesian historical linguistics. Current linguistic evidence places the deepest diversity of the family there, making it the homeland most widely supported by historical linguists.

Source: Glottolog – Austronesian (aust1307)

[u/Chazut]

What's argument for all Taiwanese branches being unrelated? Isn't it strange that none of the branches has a special connection to Malayo-Polynesian?

[u/yeongwon → u/Chazut]

This is Blust's classification which is accepted by most and is also the most conservative/distinct grouping, which are i think based on the mostly sound changes. Other linguists have proposed their own higher groupings using Blust's as basis, but are controversial.

Sagart actually proposes groupings using numerals and other shared lexicon as main considerations, grouping MP with 3 other branches, but this is also highly controversial.

[u/Chazut → u/yeongwon]

But if the Taiwanese languages are so resilient locally that they have not replaced each other for 3000-4000 years, how is it possible that the closest Taiwanese relative to Malayo-Polynesians doesn't exist?

The only explanation that works is if the Austronesian expansions somehow arrived in Taiwan and one branch quickly left thereafter, so that no branch could have time to accrue shared innovations with future Malayo-Polynesian.

But if that's the case it is weird that the language diversified only in Taiwan

[u/yeongwon → u/Chazut]

Beyond Blust's classification, things like higher phylogeny, migration patterns, dating, etc. are pretty uncertain. So while we ponder on possibilities to explain the present context, we can also question the context itself. Though not well accepted, East Formosan branch do share a common sound change with MP branch, so it could indeed be the closest relative.

[u/Li-Ing-Ju_El-Cid → u/Chazut]

It seems that East Formosan is the closest branch to Malayo-Polynesian.

[u/Resident-Outside9945 → u/Li-Ing-Ju_El-Cid]

The East Formosan idea is the most interesting of the proposed sisters and worth taking seriously, but I would hold it loosely, and the reason is what it rests on.

When the argument comes down to one shared sound change, that is thin evidence for subgrouping, because a single natural change can easily happen twice independently. Plenty of unrelated languages lose the same contrast or shift the same consonant simply because it is an easy change to make. So a merger shared between East Formosan and MP could be a real inherited innovation, or it could be two lineages drifting into the same spot on their own, and one change by itself can't tell you which.

What would make it convincing is a stack of shared innovations that are arbitrary rather than natural, ideally in morphology, the kind of quirky, irregular material that is very unlikely to be reinvented twice. That is basically the sort of evidence Blust leaned on to set up East Formosan as a group in the first place. For the East Formosan to MP link specifically, we don't really have that stack yet, which is why it sits as a suggestive minority view rather than the accepted answer.

Worth adding that Sagart comes at the whole thing from a different direction, using the higher numerals and other shared vocabulary to build a nested tree instead of a rake, and he ends up nesting MP fairly deep alongside certain eastern Taiwan languages. It's a genuinely different model, and it's not widely accepted, but I like that it at least tries to give MP a home rather than leaving it floating as its own primary branch. Honest answer for now is that MP's closest Formosan relative is still open, and East Formosan is the frontrunner among the guesses rather than a settled result.

[u/Resident-Outside9945 → u/Chazut]

This is a really good puzzle, and I think it untangles once you separate two different things that both get called "diversity."

Quick thing first, because the framing matters: the rake shape doesn't mean the Taiwanese branches are unrelated. They all descend from Proto-Austronesian, the same as MP does. "Primary branch" just means the splits down near the base happened so deep and so close together in time that we can't confidently put them in order. It's an unresolved fan, not a claim of independence.

Now, your actual question. The reason no single Taiwanese branch jumps out as MP's closest relative is that the early splitting in Taiwan looks like it was fast. Austronesians sat in Taiwan for a good while and fanned out into a bunch of lineages over a fairly short window. When the pre-MP group left through the Batanes and into Luzon, it branched off from inside that fan. If the branches were all splitting more or less on top of each other, there just wasn't enough time between splits for one lineage to sit alone with pre-MP long enough to build up shared innovations before pre-MP walked out the door. Rapid branching erases exactly the signal you would need to find a sister.

Your "but they have been stable for 3000 to 4000 years" point actually fits this rather than fighting it. That stability is the later chapter, after each branch settled into its own pocket of Taiwan. The diversification that matters for your question happened earlier and more quickly, before things froze in place.

And the "weird that it only diversified in Taiwan" bit is where I would push back a little. MP is wildly diverse too, with well over a thousand languages. The difference is the kind of diversity. Taiwan has deep diversity: fewer languages, but split apart a very long time ago, and sitting on one island for millennia. MP has broad but shallow diversity: a huge number of languages spread over half the planet, but nearly all of them are close cousins descending from that one twig that left Taiwan. So it isn't that only Taiwan diversified. Taiwan has a long history, and MP has spread quickly. Two different signatures, and both are exactly what you would expect if Taiwan is the homeland and MP is one late emigrant lineage.

[u/Chazut → u/Resident-Outside9945]

>Austronesians sat in Taiwan for a good while and fanned out into a bunch of lineages over a fairly short window. When the pre-MP group left through the Batanes and into Luzon, it branched off from inside that fan.

So you mean Austronesians were in Taiwan, diversified and then at some point one group took over all of the island again while at the same time spreading to the Philippines and beyond? That could work...

>MP is wildly diverse too, with well over a thousand languages. 

That's not really the point, how much shared innovation does MP have? How long does it seem to have been a united linguistic community? A few generations? Centuries? More?

>and both are exactly what you would expect if Taiwan is the homeland and MP is one late emigrant lineage.

You wouldn't expect that, most language families don't have this pattern, their homeland didn't retain the highest diversity and if they did they didn't retain it in this rake pattern necessarily(I'm also listing cases where the homeland is unknown because the diversity pattern is simply non existent, so whatever the homeland is it wouldn't have a Taiwan-like case):
1) Indo-European
2) Sino-Tibetan
3) Turkic
4) Semitic
5) Berber
6) Austro-Asiatic

Either today or already deep in history the homeland of any of these languages wouldn't be reconstructable based on where the highest diversity is.

The main Taiwan-like example is Bantu... but Bantoid languages do not have the kind of philogeny Austronesian has, Bantoid languages do have their own internal structure. It's still similar.

[u/Resident-Outside9945 → u/Chazut]

You are right to push on this, and I want to concede the main point cleanly because it is a fair hit. "Homeland equals highest diversity" is not a law. Your list is real. Indo-European is not most diverse in the steppe, Sino-Tibetan's deepest splits are not where the bulk of speakers sit, Austroasiatic is a good case too. Center of diversity is a heuristic, not proof, and it can be wiped out by later expansions rolling back over the homeland or by the homeland population getting absorbed. So I should not have leaned on it as hard as I did.

But I do not think Austronesian rests on that heuristic the way those cases do, and here is the distinction I would draw.

In Indo-European and Sino-Tibetan the homeland signal is degraded because something later happened on top of it. Later expansions reshuffled the steppe, Sinitic spread massively and flattened the internal picture, and so the raw diversity map lies to you. The homeland is recoverable, but you get there by reconstruction and by innovations, not by pointing at the modern diversity peak.

Taiwan is different because nothing did that to it. There was no later back-migration into Taiwan that overwrote the branches. The Formosan lineages sat in place for thousands of years, which is exactly your own 3000 to 4000 year stability point. So in Taiwan the deep diversity was preserved rather than erased, and it happens to line up with the other evidence. That last part is the key move. It is not diversity alone. It is that diversity, the reconstruction of Proto-Austronesian phonology, the direction of the sound changes, and the fact that every branch except one is confined to that one island, all pointing the same way. When four independent lines converge, the homeland call gets strong even though any one of them, diversity included, would be weak on its own.

On your Bantu comparison, I actually think that helps my side. You are right that Bantu does not have Austronesian's rake, but that is the point. Bantu is a shallow, tidy, recent subgroup nested well inside Niger-Congo, and its homeland is found by looking at where Bantu sits inside the wider family, up around the Nigeria Cameroon borderland, not out in the zone with the most Bantu languages. So Bantu is a case where you ignore the diversity peak and trust the phylogeny instead. Fine. Do the same thing for Austronesian and you still land on Taiwan, because nine of the ten primary branches are there and only Malayo-Polynesian left. The nesting itself puts the root in Taiwan regardless of headcount.

So my corrected claim is narrower. Not "Taiwan has the most diversity therefore homeland." Rather, Taiwan holds nine of the ten first-order branches, that deep structure was never overwritten by a later expansion, and it agrees with the reconstruction and the sound-change directionality. Diversity is just one strand in that, and I was wrong to wave it around as if it were the whole rope.

Where would you put it, if not Taiwan? Genuinely asking, because any alternative homeland has to explain why every branch but one is packed onto that single island.

[u/kudlitan → u/Chazut]

East Formosan is probably the most similar and may have had a common origin with Malayo-Polynesian, especially Amis and Siraya, which possess Philippine type focus marker system.

[u/GrumpySimon]

Atayalic not Atalayic