Grass & Cow

The co-evolutionary relationship between cows and grass is one of nature's underappreciated wonders; it also happens to be the key to understanding just about everything about modern meat. For grasses, which have evolved to withstand ruminant grazing, the cow maintains and expands its habitat by preventing trees and shrubs from gaining a foothold and hogging sunlight; the animal also spreads grass seed, plants it with its hooves, and fertilizes it with manure. In exchange for these services, the grasses offer ruminants a plentiful and exclusive supply of lunch. For cows (like sheep, bison, and other ruminants) have evolved the special ability to convert grass - which single-stomached creatures like us can't digest - into high-quality protein. They can do this because they possess what is surely the most highly evolved digestive organ in nature: the rumen. About the size of a medicine ball, the organ is essentially a forty-five-gallon fermentation tank in which a resident population of bacteria dines on grass.