At the time there was no Suez canal. Going from europe to China by sea would mean go around Africa which was a challenge by itself.
Although there was a Suez canal at various times in antiquity, albeit one between the Red Sea and the Nile, not the Mediterranean directly.
It's easier to sail to and from Madagascar to much of Asia than it is to sail to Madagascar across the Madagascar channel.
[0] - https://commons.wikimedia.org/wiki/File:Corrientes-oceanicas...
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It's not controversial that the Norse made it to modern day Newfoundland.
After all, being part of the same language family doesn't imply that strong a connection - English resembles, say, Farsi very very little. It just means that "the people who spoke language A at one point split off from the same people who split off to speak language B". From that angle, that the same language family is spoken in New Zealand and Madagascar is roughly as wild as the fact that homo sapiens lives in both places.
What's really wild is that modern linguistics has managed to demonstrate that the Austronesian languages are related across those vast distances and time spans.
That doesn’t take away from the wonder of imagining people thousands of years ago literally travelling across half the earth to settle somewhere else, people we usually consider as extremely different and more "primitive" than we are.
Learning that these people led in fact a life very similar to ours, were intellectually equivalent to us, had the same struggles and goals and aspirations we do (for the most part of course), is deeply fascinating, to me at least.
It really doesn't provide that evidence. Proto-Afroasiatic the oldest agreed upon hypothetical proto-language probably only dates back 18,000 years. The modern brain, vocal, and tongue structures linked to complex speech were in place 100,000 years ago, and its thought that complex speech was in place by the time Homo Sapiens left Africa 50-70,000 years ago. That's a long time for grammar to diverge. Just in recorded history plenty of languages have gained and lost very complex grammatical features. Old Chinese for example was not a tonal language, but evolved tones. Small isolated languages can change rapidly, and trade languages tend to simplify.
Why? I assume you're familiar with the idea of the same language being spoken in New Zealand and England?
It's true that Polynesian ships are smaller than English ones. But that makes no difference to... anything.
Something that I've always found interesting is how the two large Polynesian areas of Hawaii and New Zealand and currently dominated by the English language, but this domination came to New Zealand from the British Empire as it traveled east, while it arrived in Hawaii from the United States traveling west.
The English language capturing the world is unlike anything else.
Tahiti and the Marquesas fell to French, and Rapa Nui/Easter Island, to Spanish.
As a comparison, the words from the Ireland Ogham stones from the same era (4th century) written in primitive Irish (before Old Irish) are not intelligible by the modern Irish Gaeilge speakers (~200K) [1].
If interested there is open source collection of Corpus of the Inscriptions of Campā available online [2].
[1] Ogham Stones [PDF]:
https://www.heritagecouncil.ie/content/files/Ogham-Stones.pd...
[2] Corpus of the Inscriptions of Campā (Champa):
https://isaw.nyu.edu/publications/inscriptions/campa/inscrip...
I can't find the exact location though, I wonder if it's open to the public to visit?