Yes, we do. Humans share the statistical association ability that LLMs possess, but also conscious meaning and understanding. This is a difference in kind and means that we can generalize beyond the statistical pattern associations that we've extracted from data, so we don't require trillions of examples to develop knowledge.

Theoretically a human could sit alone in a dark room, knowing nothing of mathematics and come up with numbers, arithmetic algebra, etc...

They don't need to read every math textbook, paper, and online discussion in existence.

The point I'm trying to make is that I don't think we know, so we can't say either way.

In your example, would the human have ever had contact with other humans, or would it be placed in the room as a baby with no further input?

Our DNA does contain our pre-training, though. It's not true that we're an entirely blank slate.