It's not a safe bet, because there are more generalities to life than many are willing to admit. You may have some minor adaptations to high fat intake for example, but I think you can do better. Also, this sort of naive thinking will easily detach you from the original context in which salmon was eaten. In the healthiest case, frequent salmon eating probably meant eating more of the whole animal by including things like the brain and thyroid gland all while using specific preparation and cooking methods. If you approach an ancient diet with a modern mindset, you could easily make mistakes such as only eating the salmon fillets and thinking that was well-rounded nutrition.
But to dispel your obsession with your recent ancestry, one need only point to your much longer and more ancient ancestry of the line of primates that eventually resulted in humanity. They thrived with more fruits, leaves, shoots, tubers, etc. Your clan probably handles salmon eating, because mammals are flexible. Deer are known to opportunistically eat birds. Just about anything can get away with the breaking of routine to some degree. The question of whether or not a salmon diet is optimal can be derived by rat experiments of which there are many based on fish and fish oil published. The best diet in the end is the best you can come up with using the knowledge and resources at hand at a given moment.