Fours, and the end of tuna

Kottke talks about food journalist Paul Greenburg:

Humans have primarily selected four mammals (cows, pigs, sheep and goats) and four birds (chickens, turkeys, ducks and geese) to utilize for food, and are now in the process of choosing four fish (cod, salmon, tuna, and bass).

Greenburg writes in the NYT about the end of tuna:

Tuna then are both a real thing and a metaphor. Literally they are one of the last big public supplies of wild fish left in the world. Metaphorically they are the terminus of an idea: that the ocean is an endless resource where new fish can always be found. In the years to come we can treat tuna as a mile marker to zoom past on our way toward annihilating the wild ocean or as a stop sign that compels us to turn back and radically reconsider.