This is a special post for quick takes by Walker Vargas. Only they can create top-level comments. Comments here also appear on the Quick Takes page and All Posts page.
If sperm whales were sapient, and had their own languages how recently would humans have noticed? We wouldn't be able to hear much of their speech. Without the ability for advanced tool use and without agriculture, I think it would be rather hard for us to notice. I don't think this would be discovered any earlier than the 20th century. Do we know that we aren't in this situation?