Mesozoic 230 to 75/65 million years ago dinosaurs. Cenozoic 75/65 million years ago to today mammals. Of living species, primate most like insectivore (order: insectivora) Tree shrews hard to classify as primate or insectivore. Insectivore: evolved end of mesozoic, amount earliest placental mammals to evolve. Appearance of forest, bush and grassland of modern aspect with cenozoic. New plants new insects new mammals. Reorganization of environment = new exploitative possibilities or niches . Modern forested environments and earliest primates appear about same time not a coincidence. Eg: primate stereoscopic and colour vision (binocular) = depth perception needed to move about trees. Eg: open areas above ground = dispersed smells so smell less important. Eg: movement in trees = grasping hands for small limbs. Eg: vision and manipulative hand = increases in brain size to control hand-eye coordination. Refinements visual predation model = not just arboreal but visual predators. Eg: nails as claws make hand hard to close.