This era of early tool development took place during the Lower Paleolithic and was known as the Oldowan tool tradition. Anthropologists suspect that a feedback loop between brain size, behavior, and language began to develop around the time of Homo habilis, due to a proposed correlation between the gradual increase in complexity and in brain size as well as the development of more complex cultural aspects of their brains. society, like the different tools developed at the time of the habilis species. The arrival of Homo erectus around 2 million years ago marked another notable progression in biological and cultural adaptation, as well as new evidence supporting the feedback loop.