The material of the research includes A. N. Gvozdev’s diary entries entitled "From first words to the first form" and the records of the ‘speech start’ of three XXIst-century children. Taking the data into account, the author attempts to compare the speech acquisition of A. N. Gvozdev’s son Zhenya that is recorded in the above-mentioned diary and is 100 years distant from us and the author’s almost daily observation of her grandchildren’s speech development. This comparison aims to identify the constants and variables of such development. The analysis confirms the idea suggested by modern scientists that studying the formation of children’s ability to think and speak is a "clue" to many mysteries of the origin and evolution of communication. The study is based on empirical observation and takes into consideration the psychological, gender, social, and philosophical sides of the issue. The paper examines the phonetic, lexical, and grammatical aspects of children’s speech. It is claimed that each child forms laws of his/her own phonetics, and that the choice of sounds in a word to convey thoughts is a certain deliberate compromise between what he/she can pronounce and how he/she can do it to be understood. Mastering the lexical aspect of speech is closely related to the problem of children’s comprehension of the changing picture of the world. Mastering grammatical categories reflects vari[1]ations in the formation of grammatical laws in children. It is concluded that each child creates his/her language model. At the same time, the communication environment requires children to adjust the created model in compliance with the norms adopted in a particular language.