Together with their other advantages, it may help to explain how examples of the genus Homo were able to leave traces of themselves throughout most of the world outside the Americas and Australasia in the next million or so years. But we do not know for certain whether this was through the spread of one stock, or because similar creatures evolved in different places. It is generally held, though, that tool-making was carried to Asia and India (and perhaps to Europe) by migrants originally from East Africa. The establishment and survival in so many different places of these hominins must show a superior capacity to grapple with changing conditions, but in the end we do not know what was the behavioural secret which suddenly (to continue to talk in terms of prehistoric time) released that capacity and enabled them to spread over the landmass of Africa and Asia. No other mammal settled so widely and successfully before our own branch of the human family, which was eventually to occupy every continent except Antarctica, a unique biological achievement.
The next clear stage in human evolution is nothing less than a revolution in physique. After a divergence between hominins and more ape-like creatures, which occurred more than 5 million years ago, it took rather less than 2million years for one successful family of hominins to increase its brain size to about twice that of Australopithecus. One of the most important stages of this process, and some of the most crucial in the evolution of humanity, were already reached in a species called Homo erectus. It was already widespread and successful a million years ago, and had by then spread into Europe and Asia. The oldest specimen of the species so far found may be about half a million years older than that, while the last evidence for its survival (from Indonesia) suggests members of it were still living between 10000 and 15000 years ago, well after our own kind had spread throughout most of the earth. Homo erectus therefore successfully exploited a much bigger environment than earlier species and did so for much longer than has Homo sapiens, our species of modern man. Many signs once more point to an African origin and thence to a spread through Europe and Asia (where Homo erectus was fi rst found). Apart from fossils, a special tool helps to plot the distribution of the new species by defi ning areas into which Homo erectus did not spread as well as those into which he did. This is the so-called ‘hand-axe’ of stone, whose main use seems to have been for skinning and cutting up large animals (its use as an axe in the usual, hafted sense seems unlikely, but the name is established). There can be no doubt of the success of Homo erectus as a genetic product.
Sub-species of Homo erectus survived for a very long time, and, although few scholars now believe that any of these, at least in their non-African form, is one of our direct ancestors, there is no precise dividing line between them and us (there never is in human prehistory, a fact it is only too easy to overlook or forget). With the different sub-species of Homo erectus we are already dealing with a creature who has added to the upright stance of his predecessors a brain approaching that of modern man in magnitude. Though we still know only a little of the way in which the brain is organized, there is, allowing for body size, a rough correlation between size and intelligence. It is reasonable, therefore, to attribute great importance to the selection of strains with bigger brains and to reckon this a huge advance in the story of the slow accumulation of human characteristics.
Shaping of Homo Sapiens: How We Became What We Are?
