I prefer to think of double entry accounting (with reasonable controls) as the first reasonable implementation of a blockchain. At its core, a double entry accounting system is a giant ledger where each transaction is linked to the last one ‘forever’ (assuming proper controls).

It’s likely the only reasonable implementation of a blockchain but we won’t know that for sure until cryptocurrency matures enough to develop reasonable controls. I’m not holding my breathe because then it’s just an accounting system with reasonable controls built in and there are already more than enough of those built with databases.