Homo habilis had a short body and long ape-like arms like the australopithecines. But they were distinguished from earlier hominids by their big brain (c. 630 cubic centimetres) and small teeth.
The species evolved in Africa at a time when traditional forest foods like fruit were becoming scarce forcing animals to seek out new nutritional sources.
Homo habilis ate meat by scavenging from animal carcasses. But snatching meat from under the noses of fearsome predators like lions was a risky business.
However, Homo habilis had a secret weapon: stone tools. Crude stone implements were used to smash open animal bones and extract the nutritious bone marrow.
Homo habilis lived in East Africa at the same time as Paranthropus boisei. But they they occupied different ecological niches and so were not direct competitors. While habilis was an omnivore, boisei survived on a hard-to-chew vegetarian diet.
Because meat is rich in calories and nutrients, easy-to-digest food, early Homo lost the need for big intestines like apes and earlier hominids had. This freed up energy for use by other organs. This surplus of energy seems to have been diverted to one organ in particular: the brain.
But scavenging meat from under the noses of big cats is a risky business, so good scavengers needed to be smart. At this stage in our evolution, a big brain was associated with greater intellect.
Big brains require lots of energy to operate: the human brain uses 20% of the bodyís total energy production. But the massive calorific hit provided by meat kick-started an increase in the brain size of early humans.
But around two million years ago, telltale cut marks on the surface of animal bones reveal that early humans were using crude stone tools to smash open the bones and extract the marrow.
Primitive stone 'Oldowan' tools helped habilis get at bone marrow
Stone tools allowed early Homo to get at a food source that no other creature was able to obtain: bone marrow. Bone marrow contains long chain fatty acids that are vital for brain growth and development. This helped further fuel the increase in brain size, allowing our ancestors to make more complex tools.
The tools made by habilis are called 'Oldowan tools'. The process used to make these tools was incredibly simple. Hominids picked up one stone, known as a core, and broke it with another, known as a hammerstone or percussor. This gave them a sharp cutting edge that could pass through an animalís hide.