Primates is a taxonomic unit including humans. It is called primates because humans regard themselves as the highest product of evolutionary history and believe that humans are at the top of the biological evolution ladder, the leader of all souls and the ruler of the world. However, primates originated directly from the ancestors of primitive insectivores. From the evolutionary tree of mammals, primates are an early branch.
Since the earliest primates evolved from insectivores, they should have similarities with some insectivores. Today, tree shrews, feather tailed tree shrews and their relatives living in Asia are quite similar to the earliest primates in morphology. The tree shrew is a small mammal the size of a squirrel. Its head extends forward with a long snout and a long tail behind it. They are classified as insectivores, but in fact, they have more fruits than insects in their food sources.
In the early Cenozoic, primates have developed from tree shrew like ancestors in different directions and produced various branches. One is represented by lemurs and lazy monkeys, which is called protomonkey suborder; The other is represented by the spectacled monkey and subsequent monkeys, apes and humans, which is called the anthropoid ape suborder. Spectacled monkeys are in the most primitive position in the suborder of apes, while German monkeys are the most primitive type of spectacled monkeys. It can be said that German monkeys should be the ancestors of monkeys.
The fossils of Asian German monkeys found in Hengdong, Hunan, China, in the early Eocene 55 million years ago have almost complete skulls and upper and lower teeth, while the fossils of German monkeys previously found in North America and Europe are only scattered teeth and broken jaws.
Morphological and taxonomic analysis shows that Asian German monkeys are the most primitive among the six known German monkeys and the earliest primates found so far. The Asian German monkey weighs only about 28 grams and its head is only 2.5 centimeters long. It is not as big as a fist. It is much smaller than all primates living in the world today. It has two rows of tiny teeth, a relatively large orbit and a larger infraorbital foramen for the passage of the trigeminal nerve, which means that there are more developed tentacles. According to the unearthed fossils, it is inferred that the Hengyang Basin in Hunan Province in the early Eocene was a huge lake. The German monkey lived in the jungle beside the lake and ate insects.