Not may people appreciate that at the peak of the last ice age, "sea level" was 400 feet lower than it is today. It's likely that there's a whole bunch of archaeological sites that we can't easily get to right now, even if we could find them.
For instance, Indonesia would have been connected to Australia more or less and so one could cross over land from Southeast Asia to Australia.
At the last glacial maximum (and sea-level minimum), the big islands of Sumatra, Java, and Borneo would have been portions of a massive Southeast Asia peninsula. In addition, New Guinea would have been attached to Australia. The other Indonesian islands, such as Sulawesi and Timor, would still have been islands. The gaps between the islands would be somewhat smaller, perhaps about 25mi (even between Timor and Australia), which is close enough that you can sail between them without ever losing sight of land.
https://en.wikipedia.org/wiki/Doggerland
It's amazing how in a short period of time ( in geological terms though it seems like a lot of time for us ), how much of the earth changed.
Another interesting tidbit, we had a little ice age not too long ago which ended in the mid 1800s.