The given diagram illustrates the changes in cutting tools that ancient people used for everyday life and tasks during the Stone Age (1.4 and 0.8 million 
years
 ago).
Overview, it can be seen that the Use synonyms
side
 Use synonyms
view
 of the tools had become Use synonyms
more 
narrow and ancient people started to use two sides Correct quantifier usage
apply
instead
 of one for cutting after 600 thousand Linking Words
years
.
Analyzing the given diagram, it can be noticed that the front Use synonyms
view
 of  Use synonyms
tool
 A is sharp on one Use synonyms
side
 and it had a triangular form 1.4 million Use synonyms
years
 ago. The Use synonyms
side
 Use synonyms
view
 of Use synonyms
this
 Linking Words
tool
 was thick and the back Use synonyms
view
 had a small place for a finger to hold. After 600 thousand Use synonyms
years
, ancient people  started to use a new Use synonyms
tool
 B for cutting. It had an oval form and two sharp sides. The Use synonyms
side
 Use synonyms
view
 of the new Use synonyms
tool
 was narrower than the previous Use synonyms
tool
 and the back Use synonyms
view
 had a more comfortable place for holding in the center of the stone.Use synonyms