The branch from the place where Appaya evolved into half-monkeys (lemurs, loris, tarsiers and galagos) can be drawn and then this is also possible at the branch between half-apes and apes. This makes comparison between fossil apes and great apes easier and easier to draw.
Smell outstripped
As jumping, grabbing and catching became a lifestyle, the sense of smell became less important than sight. This is especially important for an animal that lived in a three-dimensional world of trees and not in the two-dimensional world of the flat ground. In addition, the tree-dwelling animal had to be able to continuously and accurately judge how far a branch or a lizard was from him. In response to the growing importance of seeing over smelling, the head of the primordial Appaya began to change as well.
Changes to the head of the primordial tupaya
The Upaja’s snout became shorter, the skull rounder. The eyes widened and gradually moved to the front of the head, where the field of vision of one eye could overlap that of the other. This caused the animal to see binocular (stereoscopic).
Evolution of the brain
An animal with binocular vision can judge distances much better than an animal with eyes on the side of the head (such as a rabbit). Rabbits should be wary of side or rear attacks. Eating grass also does not require a high degree of intelligence, at least less than hunting hard-to-reach prey in the treetops. As a result, over time, the tree dwellers’ rounder skulls began to contain larger brains.
New animal group: the primates
Within 10 or 20 million years, those changes were sufficiently advanced to be able to speak of a distinctly new animal group: the primates. The earliest examples are the half-monkeys. As with the Appajas, half-monkeys also have descendants that are still alive (lemurs, lories, tarsiers and galagos). Some of them (especially the great lemurs) are very similar to monkeys and they also act like monkeys. If monkeys never emerged, lemurs would likely still live in places where monkeys are now found.
Origin of the monkeys
Unfortunately for the lemurs, the monkeys did evolve. They provided another branch in the primate family tree. Initially you could actually only speak of the latest model super lemur. The differences between those super lemurs and the common old-style members of the lemur population were too small to be of much importance. But as these differences became more pronounced (because they offered greater chances of survival), the trees filled more with more intelligent, faster, more useful, and generally more skilled descendants (who could eventually be called apes). In most places the lemurs gradually disappeared because they could not compete with the competition. Where they still exist (like in Madagascar) it is because there are no monkeys there or have ever been there. For example, another branch could be drawn (one that goes back quite far) to indicate the split between half-monkeys and monkeys.
Split between monkeys and great apes
If you go up along the monkey branch, you will reach the next branch, namely the junction between apes and apes. The evidence for this split can be found in the chewing surface cusps of the molars. A branch that took place more than 15 million years ago. A monkey’s molar has chewing surfaces that count four crown nodules arranged two by two. A great ape usually has five lumps. These crown nodules do not lie in pairs, but in a characteristic Y-shaped pattern. This Y-shaped pattern is a primitive state and is found in the common ancestor of the ape and ape.