The primate fossil record for this crucial transitional period leading to australopithecines is still scanty and somewhat confusing.
However, by about 4.2 million years ago, unquestionable australopithecines were present.
Fossil dating maps
As the australopithecines evolved, they exploited more types of environments.
Their early proto-hominin ancestors had been predominantly tropical forest animals.
One line apparently was adapted primarily to the food resources in lake margin grassland environments and had an omnivorous diet that increasingly included meat.
Among them were our early human ancestors who started to make stone tools by this time.
Over the last decade, there have been a number of important fossil discoveries in Africa of what may be very early transitional ape/hominins, or proto-hominins.
These creatures lived just after the divergence from our common hominid ancestor with chimpanzees and bonobos, during the late Miocene and early Pliocene Epochs.The fossils have been tentatively classified as members of three distinct genera-- .Sahelanthropus was the earliest, dating 7-6 million years ago.The classification of Sahelanthropus has been the most in question.The earliest australopithecines very likely did not evolve until 5 million years ago or shortly thereafter (during the beginning of the Pliocene Epoch) in East Africa.It is likely that all of the early hominins, including humans, supplemented their diets with protein and fat rich termites and ants just as some chimpanzees do today.