What we call "copyright" is, as it is referred to in the constitution, a monopoly granted by the government. All your other rights are assumed to exist because it would be outlandish to say a mere government could "grant" them. They are protected by the government, or so it was intended.
Unlike real rights, Congress could pass a law setting the term of such a monopoly to zero and there would be no civil rights argument against doing so. Patents and copyright are nothing like your actual rights.
This applies to the way copyright law is authorized constitutionally in the US. YMMV.
Moving away from land ownership, you get forms of property rights that are even harder to reconcile with the idea of natural rights. Mineral rights, shipping rights, air rights, spectrum rights, toll rights, salvage rights, etc. None of these things are meaningful absent the concept of a legal system enforced by a government.
What if the author dies shortly after creating the work, and was hoping to support their family on the proceeds?