Let's say that it's scientifically proven that ghosts exist. Would they then stop being supernatural and become natural, thus making it impossible to ever have proof of the supernatural?
Your source doesn't specifically say the word "superorganism", but that is what the idea of the superorganic points to - a higher level superorganism, the same as a bee hive, a termite nest, or an ant colony...
It doesn't refer to any ability/inability to understand culture, which was my main point.
Yeah, because they believe in ghosts, they don't know they're real...
If you can't definitively, scientifically prove ghosts exist, then there is no way to understand how they work in nature, ergo they're supernatural. I don't think it's that vague...
We don't know the exact cause of life on earth, doesn't mean all life on Earth (including you) is supernatural.