Evolution of Hearing

Evolution of hearing dates back to some 250 million years ago along with mammalian evolution. To understand the evolution of hearing, one needs to understand the basic mammalian evolution first. Beginning of mammal evolution first seen in Triassic period about 230 million years ago, during which all land vertebrates developed tympanic middle ear. Mammals with their various characteristic traits, arose during the Triassic period some 250 million years ago and quickly gave rise to number of separate lineages. From Triassic, evolved the jurrasic (200 million years ago) followed by the cretaceous (100 million years ago). Multituberculata (middle of lineages) formed the major group in creataceous. Cenozoic evolved from cretaceous (50 million years ago). Monotremes (egg laying mammals) forms the major group here. The THERIANS (modern mammals that does not lay eggs) split into marsupials and placentals during the cretaceous period and are the dominant creatures today.