Why it is impossible to single out one universal criterion for a species.

There is no absolute view criterion, because each of them characterizes only one of many aspects of the life of individuals of a species, which, for example, may coincide in different species.

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.