The Emergence of Our Human Ancestors: The Appearance of Homo Habilis About 2.5 Million Years Ago

Approximately 2.5 million years ago, during the Miocene Epoch, a series of interrelated events took place that had a significant effect on the evolution of our ancestors. There was a dramatic change in climate which produced drying and cooler climatic conditions including glaciation. This was particularly true in Africa which was also being affected by the uplift of the mountains in eastern Africa. Much of the tropical forests were eliminated and replaced by grass lands. This meant that the Australopithecines lost much of their sources of food, the trees with fruit and berries.

The genus Homo, taken from the Latin, meaning "human being", or "person," evolved as a genus from Australopithecine ancestors with the initial appearance of Homo habilis. Commonly referred to as "handy man", Habilis was so called because of evidence of tools found with its remains. H. Habilis lived between 2.4 and 1.5 million years ago. As a genus, Habilis shared a number of similarities to the australopithecines. Habilis had a primitive looking face that bore many similarities to the australopithecines. The molars were small, but were still much larger than those found in modern humans. The average brain size, at 650 cc, is considerably larger than in australopithecines. The shape of Habilis' brain was also more humanlike. Habilis might have contained a form of a rudimentary Broca's area which is essential for speech, and habilis might of been capable of producing rudimentary speech. Habilis was about 5 foot tall, and weighed about 100 pounds at maturity, although females may have been smaller.

The appearance of the H. Habilis line of development coincides with the first evidence of stone tools with primary reference to the Oldowan toolkit which was made by H. Habilis from flint. "The technology is called 'Oldowan' because the first specimens were found by Louis and Mary Leakey at Olduvai Gorge. Oldowan tools have been described as 'crude but effective';... Most of the tools were made by a single blow of one stone against another, to produce a sharp-edged flake. But for some of them, a softer rounded hammer stone was needed to achieve the right effect."

Another distinguishing characteristic of the Oldowan Toolkit is that they were non-symmetrical as shown in this depiction by José-Manuel Benito, and from Wikipedia.


Evolutionary developments were combined with technological innovations and cultural forms that coalesced around human growth as a species. The result of technological and cultural changes which vastly sped up the development of intellect and resulted in a quickening pace of change for human development.We have already seen the effect of Oldowan Toolkits as early examples of technological developments and innovations are clearly demonstrated by the creation of established practices to create stone tools which pushed humans to constantly be innovative and to seek better and better refinements in the use of flint and the control of fire. Both flint tools and the control of fire pushed humanity forward as each provided protection and access to sources of sustenance. Flint and fire translated into human access to power and control over the environment.

The use of brain power or modes of behavior is a highly distinguishing characteristic of human ancestors beginning with H. Habilis' ability to create diets that consisted of higher nutritional components. And the inclusion of the high concentrations of protein, calories, and fat found in meat brought forth changes in dental structures and in the facial bones. A non-physical aspect of dietary change was witnessed in the continued refinement and use of tools. And of equal if not revolutionary importance was that the move to becoming carniverous meant that H. Habilis began to span across a wider geographic range than previous hominids as the search for new sources of meat drove Habilis farther away from a centrally based location to greater vistas.

H.Habilis also developed a focused spatial and temporal sense, commonly referred to as foresight that provided the means for producing tools. H. Habilis is known to have created stores of rock that were to be used for the creation of more tools in the future and also because H.Habilis saw the need for specialization, tools were produced with very specific tasks in mind. The use of forethought and the movement from general tools to specifically modified tools designed to accomplish a particular tasks directly reflects H.Habilis use of an expanding brain power.

Factors Affecting Hominin Evolution Before 5 Million Years Ago: The Introduction of the Australopithecines

Some 5 million years ago during the beginning of the Pliocene Epoch climatic changes were causing African forests to progressively reduce their geographic coverage as grasslands, or savannas were advancing across the landscape.the genealogy of apes and human like creatures begin to leave a fossil record that signaled and divergence and the beginnings of separate developmental path.

Hominids were represented by the emergence of the genus australopithecines (southern ape) of which several varieties developed over time and emerged from the South African region as demonstrated by the many fossil findings in the proximate Great Rift Valley. These fossil findings showed that early hominins had almost human-like bodies below the neck but brains that were very little changed in size from those of apes. This point has been established in our previous postings but needs to be re-established to set the scene for the bifurcation of the australopithecine lineage into at least 2 evolutionary lines of hominins descended from the early australopithecines.

One line, often referred to as the gracile or slim and slender form included Australopithecus anamensis, Australopithecus africanus and Australopithecus afarensis. A. africanus and A. afarensis apparently were adapted primarily to lake margin grassland environments and had an omnivorous diet that increasingly included meat. Among them were our early human ancestors who started to make stone tools by this time.

The other lineage, referred to as the robust forms which included types such as Australopithecus aethiopicus, Australopithecus boisei and Australopithecus robustus lived more in mixed grassland and woodland environments, was primarily vegetarian much the same as their australopithecine fore bearers and had become extinct by about a million years ago.

What all australopithecines had in common among each of the various varieties, was a preference for bipedalism. In addition, they may also have used sticks and stones to fight, for they did not possess the type of canine teeth that would have made very imposing. Australopithecine brain cases were only capable of holding approximately 35% of the total volume that a modern human can contain. Australopithecines stood approximately four and a half feet tall. A very important point to consider about the Australopithecines was that their bipedalism came before the development of large brains, a factor long thought to be quite the opposite for many researchers and scientists.