Read the wording of the biogenetic law. How, in the individual development of any organism, the phylogenesis of the species to which this organism belongs is briefly and quickly repeated.
The zygote is the first stage of development of all multicellular organisms. In all vertebrates, including higher ones, a chord is laid, which is further replaced by the spine. During embryonic development of birds and mammals, including humans, gill slits appear in the pharynx and corresponding partitions. The structure of the heart of a human embryo resembles during this period the structure of this organ in fish. Thus, Ontogenesis (individual development) of each individual is a short and rapid repetition of phylogenesis (historical development) of the species to which this individual belongs.
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.