Homo habilis
Progressing along the human ancestral timeline, brain size continues to steadily increase (see "Homininae") when moving into the era of "Homo". For example, "Homo habilis", living 2.4 million to 1.4 million years ago and argued to be the first "Homo" species based on a host of characteristics, had a cranial capacity of around 600 cm3. "Homo habilis" is estimated to have had ~40 billion neurons.