Overview:

This species, one of the earliest members of the genus Homo, has a slightly larger braincase and smaller face and teeth than in Australopithecus or older hominin species. But it still retains some ape-like features, including long arms and a moderately-prognathic face.

Its name, which means ‘handy man’, was given in 1964 because this species was thought to represent the first maker of stone tools.  Currently, the oldest stone tools are dated slightly older than the oldest evidence of the genus Homo.

History of Discovery:

A team led by scientists Louis and Mary Leakey uncovered the fossilized remains of a unique early human between 1960 and 1963 at Olduvai Gorge in Tanzania. The type speciman, OH 7, was found by Jonathan Leakey, so was nicknamed "Jonny's child". Because this early human had a combination of features different from those seen in Australopithecus, Louis Leakey, South African scientist Philip Tobias, and British scientist John Napier declared these fossils a new species, and called them Homo habilis (meaning 'handy man'), because they suspected that it was this slightly larger-brained early human that made the thousands of stone tools also found at Olduvai Gorge.

How They Survived:

Early Homo had smaller teeth than Australopithecus, but their tooth enamel was still thick and their jaws were still strong, indicating their teeth were still adapted chewing some hard foods (possibly only seasonally when their preferred foods became less available).  Dental microwear studies suggest that the diet of H. habilis was flexible and versatile and that they were capable of eating a broad range of foods, including some tougher foods like leaves, woody plants, and some animal tissues, but that they did not routinely consume or specialize in eating hard foods like brittle nuts or seeds, dried meat, or very hard tubers.

Another line of evidence for the diet of H. habilis comes from some of the earliest cut- and percussion-marked bones, found back to 2.6 million years ago. Scientists usually associate these traces of butchery of large animals, direct evidence of  meat and marrow eating, with the earliest appearance of the genus Homo, including  H. habilis.

Many scientists think early Homo, including H. habilis, made and used the first stone tools found in the archaeological record—these also date back to about 2.6 million years ago; however, this hypothesis is difficult to test because several other species of early human lived at the same time, and in the same geographic area, as where traces of the earliest tool use have been found.

Evolutionary Tree Information:

This species, along with H. rudolfensis, is one of the earliest members of the genus Homo. Many scientists think it is an ancestor of later species of Homo, possibly on our own branch of the family tree. Naming this species required a redefining of the genus Homo (e.g., reducing the lower limit of brain size), sparking an enormous debate about the validity of this species.

While scientists used to think that H. habilis was the ancestor of Homo erectus, recent discoveries in 2000 of a relatively late 1.44 million-year-old Homo habilis (KNM-ER 42703) and a relatively early 1.55 million-year-old H. erectus (KNM-ER 42700) from the same area of northern Kenya (Ileret, Lake Turkana) challenged the conventional view that these species evolved one after the other. Instead, this evidence - along with other fossils - demonstrate that they co-existed in Eastern Africa for almost half a million years.

Questions:

We don’t know everything about our early ancestors—but we keep learning more! Paleoanthropologists are constantly in the field, excavating new areas, using groundbreaking technology, and continually filling in some of the gaps about our understanding of human evolution.

Below are some of the still unanswered questions about Homo habilis that may be answered with future discoveries:

1. Was H. habilis on the evolutionary lineage that evolved into later species of Homo and even perhaps our species, Homo sapiens?
2. Are H. habilis and Homo rudolfensis indeed different species, or are they part of a single, variable species? Or was one the ancestor of the other?
3. If H. habilis is not the ancestor of Homo erectus, how does it fit into our evolutionary tree?
4. H. habilis is one of the earliest members of the genus Homo. Was there a relationship between the origin of this genus and climate change – either with an increased period of climatic fluctuations, or major episodes of global cooling and drying leading to the spread of C4 grasslands?

References:

First paper:

Leakey, L.S.B., Tobias, P.V., Napier, J.R., 1964. A new species of the genus Homo from Olduvai Gorge. Nature 202, 7-9. 

Other recommended readings:

Bobe, R., Behrensmeyer, A.K., 2004. The expansion of grassland systems in Africa in relation to mammalian evolution and the origin of the genus Homo. Palaeogeography, Palaeoclimatology, Palaeoecology 207, 399-420.

Domínguez-Rodrigo, M., Pickering, T.R., Semaw, S., Rogers, M.J., 2005. Cutmarked bones from Pliocene archaeological sites at Gona, Afar, Ethiopia: Implications for the functions of the world’s oldest stone tools. Journal of Human Evolution 48, 109-121.

Haeusler, M., McHenry, H., 2004. Body proportions of Homo habilis reviewed. Journal of Human Evolution 46, 433-465.

Spoor, F., Leakey, M.G., Gathogo, P.N., Brown, F.H., Antón, S.C., McDougall, I., Kiarie, C. Manthi, F.K,  Leakey, L.N., 2007. Implications of new early Homo fossils from Ileret, east of Lake Turkana, Kenya. Nature 448, 688–691. 

Ungar, P.S., Grine, F.E., Teaford, M.F., El-Zaatari, S., 2006. Dental microwear and diets of African early Homo. Journal of Human Evoution 50, 78–95

 Ungar, P.S., Grine, F.E., Teaford, M.F., 2006. Diet in early Homo: a review of the evidence and a new model of adaptive versatility. Annual Review of Anthropology 35, 209-228.