Passage Between two and three million years ago, several fundamental stages of human development took place: the first use of tools, an expansion of diet to include meat, changes in habitat and posture, an increase in brain size, and, finally, the emergence of Homo sapiens 

The purpose of the passage is to 

explain how larger brains helped humans make and use tools 

 list important aspects of human development

 suggest that tools allowed humans to begin eating

 show how posture and habitat affected brain size