There is great debate as to whether genus Homo, the human genus, descends from Australopithecus afarensis or Australopithecus africanusor something we havent found yet. The fossil record from about two and a half to two million years ago is very poor. Louis Leakey called this species Homo habilis, or handy man, because he associated it with the use of stone tools. Stone tools did emerge in that sketchy period, but we dont really know who invented the first examples.
Note: Some researchers divide hominids of this era into two species, H. habilis and H. rudolfensis.
Photograph at left and top by Kenneth Garrett