Archaeologists tell us humans have been eating crustaceans (lobsters, crabs, shrimp) from prehistoric times to present.
They know this from excavating "middens," deposits of shells and bones left by early civilizations.
These foods weren't "discovered" (like early people "discovered" some corn popped if placed near the fire) but noticed.
The earliest hunter-gatherers took advantage of every available food resource.
One of theses features, Intimate Encounters (IE), was a subset of Plenty of Fish for those explicitly seeking sexual partners without having to shoulder the burden of a relationship.