CENOZOIC: The most recent geological era in the Earth’s history, in which mammals came to dominate animal life. The Cenozoic runs from 66.4 million years ago to the present and began when Asia acquired its present appearance and mammals came to dominate animal life. The most important tectonic event in the Cenozoic history of Asia was its collision with India some 50 million years ago. This collision took place some 2100 km (1250 miles) farther south of the present location of the line of collision along the Indus–Brahmaputra suture behind the main range of the Himalayas. The Cenozoic includes the Tertiary and Quaternary periods.