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. People who lived near water (oceans, seas, lakes, rivers) naturally took advantage of the foods offered by these resources.
Culinary evidence confirms lobsters were known to ancient Romans and Greeks. The were highly esteemed by the British, not so esteemed by American colonists. This sea creature enjoyed a resurgence of demand in the 19th century which still holds true today.
http://www.foodtimeline.org/foodlobster.html
In North America, the American lobster did not achieve popularity until the mid-19th century, when New Yorkers and Bostonians developed a taste for it. Prior to this time, lobster was considered a mark of poverty or as a food for indentured servants or lower members of society in Maine, Massachusetts, and the Canadian Maritimes, and servants specified in employment agreements that they would not eat lobster more than twice per week. Lobster was also commonly served in prisons, much to the displeasure of inmates.
https://en.wikipedia.org/wiki/Lobster
