Southeast Asia had a million square miles of prime habitat, now underwater, until only 20,000 years ago. It stretched south/east from Korea, connecting Taiwan t

Southeast Asia had a million square miles of prime habitat, now underwater, until only 20,000 years ago. It stretched south/east from Korea, connecting Taiwan to the mainland, east off Viet Nam and south all the way to Borneo, Sumatra, and Java. We call it Sundaland today. Indonesia occupies its mountaintops. There was time and space enough there for a whole civilization as sophisticated as ancient Egypt to rise and fall and rise again, and finally be submerged. People who lived there, and had to move uphill as the sea claimed their great-grandparents' homes, might retain no hint of their ancestors' achievements. Something similar could have happened in the middle of the Sahara, and now be under sand dunes, instead. With no trading partners, there would be no expectation of artifacts remaining to be found elsewhere. We might never find any hint of such a civilization, if they existed. ("Atlantis", you may say, but that is just a tale.) The Amazon rain forest once held tens of millions of people living in major cities, maintaining the whole Amazon basin as an orchard they had domesticated for at least 10,000 years. We had no hint of any of it until barely 50 years ago. What is left of their specialized knowledge, beyond subtle ayahuasca, manioc, and cacao processing? (Sweet potato, anyway, reached the Pacific Islands.) Their civilization was apparently wiped out by the assortment of diseases brought by Europeans, and vanished beneath the unchecked forest in only a century. We should not believe in anything without evidence, but it would be foolish not to continue seeking such evidence everywhere it might be.