Seafarer descendants changed their noses
South American primates have evolved differently as compared to their African and Asian relatives. The most striking difference is right in the middle of their faces. The noses of the South American monkeys and apes are typically more flat, and their nostrils point to the sides, whereas those of African monkeys and apes are facing downwards. The latter group includes humans and other apes.
South American monkeys have stronger, more flexible tails that can be used to hold on to branches. Many African monkeys have developed large, often colourful pads on their hind parts, which they use to sit on and to send signals to their peers.