Abstract: The ability to use indirect tools is one of the main intelligence boundaries in differentiating human beings from modern chinipanzee. In the early stages of child education, introducing indirect tool-using games and training is a necessary means of developing the child's abi- lity to its optimal phenotype. This paper presents the results of care- ful study on the development of tool-using behavior (in children from 1.5 to 5.5 years of age) and its relation with language development and with the separation of subject and object. The results show that direct tool-using ability almost appears at the same time as the lang- uage development and subject-object separation, but the indirect tool- using ability is found to begin much later, usually at about 3-4 years of age. All these indicate: (1) The starting point of modern anthro- pological study should not focus on direct tool-making×language de- velopment×the separation of subject,but on the stages after that. (2) The age of about 3.5 is the best time to introduce tool-using games or training and also a turning period in which the level of intelligence development of the child is beyond the animal. (3) The intelligence recapitulation theory contradicts to the conjecture that humans had no spoken language until created by the homo sapiens or homo erectus at a later period.

Key words: children, development, intelligence boundary, tool-using behavior, anthropological study, recapitulation and reformation