The common term for members of the monocotyledon family Graminae. This family contains approximately 9000 species with global distribution. The majority are perennial with long narrow leaves, hollow stems and hermaphroditic flowers. The evolution of grass triggered significant changes in Earth life. It created a novel type of habitat, in which Humans would eventually evolve. Of all Humanity's early domesticates, only one --the cat --was not shaped by the evolutionary pressures imposed by the grasslands.
The key evolutionary innovation of the grasses is their growth pattern. While other plants grow from their tips, grasses grow from their base. Rather than the above-ground bulk of most plants (that block lines of sight and impede movement) the stems of grasses grow underground. This allows them to sustain a significantly greater biomass per square kilometer than could previously existing shrubs. Grazing herbivores could be both large and social, unlike the browsers that preceded them. Adaptations for speed also became more common. The existence of herbivore herds in turn promoted the evolution of social carnivores (lions, wolves, etc.) all of which possess a significant amounts of potential. Ultimately these ecological changes set the stage for the evolution of Humanity. (by Robert Shaw, contributing editor)
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