Typical signs of first animals: they have a cloaca like reptiles, lay eggs, body temperature up to +30 degrees and drops or rises, depending on the ambient temperature, by 5-6 degrees. They are fed with milk, which flows down the enlarged pores along the wool of the female and the cubs lick it. The body is covered with hair or needles. The first animals include the platypus and the echidna.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.