That comes down to the (philosophical) question if natural numbers existed before the first human started thinking about them. Depending on this the Peano axiom

That comes down to the (philosophical) question if natural numbers existed before the first human started thinking about them. Depending on this the Peano axioms either just describe a part of the universe or they introduce something new. (I don't think it matters that natural numbers were known before the Peano axioms were formulated - before that we just defined natural numbers in a less formal way.)