one usually comes to this question while studying the evolution of the hand. The development of power grip probably preceded the precision grip.
According to napier, In the precision grip the thumb is abducted in both the metacarpophalangeal and the carpometacarpal joints, whereas in the power grip both joints are abducted. These patterns,either separately or in combination, provide the anatomical basis for all prehensile activities whether skilled or unskilled.
prehensile activities, whether skilled or unskilled"