Quirks & Quarks has a story in their January 24th, 2015 podcast on Australopithecus africanus and potential tool usage.  By studing the structure of hand bones, it has been determined that A. africanus had sufficient grip strength to use tools.  The study looked at the structure of the inner trabecular bone.

The earliest known use of stone tools is from 2.6 million years ago. They were made by a species of hominin known as Homo habilis. Making stone tools and using them is only possible with the capability to make a precision grip with an opposable thumb. Human hands have that capability, but not our great ape relatives.

Dr. Tracy Kivell – a Canadian scientist and Reader of Biological Anthropology at the University of Kent in England – has recently studied a fossil from the hand of Australopithecus africanus, a species that lived up to 3 million years ago and not associated with stone tool use.

The structure of the inner trabecular bone indicates that this hand was able to make such a grip, and could have made stone or other tools, one-half million years earlier than previously thought.

Original paper in Science