Arboreal to Terrestrial: Beginning approximately 9 million years ago, our ancestors began an evolutionary change from forests to woodlands to savannahs. This gradual transition from primarily arboreal (tree-dwelling) lifestyles to increasingly terrestrial (ground-based) behaviors was very gradual with traits specific for walking around carrying things gradually accumulating. This evolutionary journey spanned roughly 7 million years, culminating in species like Homo habilis, which by about 2 million years ago, had adapted to spend most of their time on the ground and carrying things like stone tools and likely walking sticks which were also used to hunt and fight off animals.