"Proof of humanity" is an active area of research, and there are several attempts at it out there. One that's worth looking at is BrightID[0] (although some people might be put off by it being blockchain-adjacent, in that it uses a DAO as part of its consensus-building system).
As for the difference between pseudonymity and anonymity, it's worth noting that once everyone has a cryptographic identity, we can start layering on clever things like zero-knowledge proofs, for example, which would allow people to issue themselves new pseudonyms that carry the same level of trust as their core identity, without ever revealing what that core identity is (or which other accounts vouched for the core identity to give it that level of trust).
As for the difference between pseudonymity and anonymity, it's worth noting that once everyone has a cryptographic identity, we can start layering on clever things like zero-knowledge proofs, for example, which would allow people to issue themselves new pseudonyms that carry the same level of trust as their core identity, without ever revealing what that core identity is (or which other accounts vouched for the core identity to give it that level of trust).
[0] https://www.brightid.org/