Gall’s law

From Systemantics: How Systems Really Work and How They Fail by John Gall

A complex system that works is invariably found to have evolved from a simple system that worked. A complex system designed from scratch never works and cannot be patched up to make it work. You have to start over with a working simple system.

If you think about it, this is also applicable for evolution. Nature never creates new species. It evolves the existing ones. Single cell organisms to multi cell organisms. Leopard to snow leopard. Apes to humans.