Evidence from a quarry in southern England is shedding extraordinary new light on the evolution of human intelligence.
Arguably, the most important driving force that enabled early humans to evolve into ever more intelligent creatures was the human hand, which gave us the physical ability to make things.
Without that crucial ability, there would never have been the need to imagine and visualise complex objects purely in the mind, or the ability to then invent, manufacture and use them.
Now archaeologists have demonstrated for the first time that a particular type of stone tool used some half a million years ago could not have been made without modern human-like hands.
The study – based on beautifully made prehistoric tools found at Boxgrove in West Sussex – reveals for the first time that early Stone Age humans had modern-style human hands, despite the fact that they belonged to a human species ancestral to our own but which became extinct more than 300,000 years ago.
Research in the UK and the US supports the concept that early human intellectual ability was largely developed in tandem with, and to a considerable extent courtesy of, hand evolution – and that eventually we (Homo sapiens) inherited our super-dextrous hands from prehistoric humans, which existed before the Neanderthals.
The specific stone tools which were analysed as part of the study were sophisticated flint hand axes, which had required a special technique to shape them.
The technique is known to prehistorians as ‘platform preparation’. In most very early stone tools, the manufacturing process is a simple single-stage affair in which the toolmaker merely hits a lump of flint with a stone repeatedly to systematically knock bits off it until the lump has been reduced to a desired shape.
However, more sophisticated toolmakers employed a two-stage approach. First they would successively "soften up" small portions of the flint’s surface, so as to then be able to more accurately remove flakes from it, thus creating a much more sophisticated and effective tool with a better and more refined cutting edge.
By attaching electronic sensors to the hands of skilled modern flint knappers, archaeologists from the University of Kent were able to demonstrate that "platform preparation" – and thus more sophisticated stone tools – was only achievable by prehistoric people equipped with anatomically modern human-like hands.
The study, led by Dr Alastair Key of the university’s School of Anthropology and Conservation, and funded by the British Academy, investigated how hands were used during the production of different types of early stone tools.
The research demonstrates that the Boxgrove early humans probably had significantly stronger grips compared to earlier populations.
It reveals that by 500,000 BC, humans had the physical capability needed to make sophisticated hand axes.
This in turn implies that they were also theoretically able to make a large range of other artefacts that required strong, dextrous hands – things made out of wood, antler and bone, as well as stone.
“Our experimental research not only suggests that early humans at least 500,000 years ago had anatomically modern human-like hands, but, when combined with other recent research, can also help us understand the way in which the human hand, brain and other anatomical elements co-evolved,” said Dr Key.
Although the fact that sophisticated tool manufacture could only be done with modern-human-like hands was demonstrated by the Boxgrove research, another set of similarly sophisticated tools have recently been found in South Africa (also dating from around 500,000 years ago) – and there are indications that "platform preparation" (the crucial diagnostic sophisticated technique) was being used for stone tool manufacture in Ethiopia as early as 850,000 years ago.
So the Boxgrove, the South African and the Ethiopian evidence now helps demonstrate quite clearly that humanity developed its manual dexterity, its intelligence and its manufacturing ability as part of a long interactive process across at least two and probably three continents.
Early (and indeed modern) humans were (and still are) not physically the strongest or even the fastest animals around. So, in order to survive, they had to evolve ways of administering physical force through their hands in ever more efficient ways. They needed to do that in order to hunt and gather more efficiently, in order to butcher prey more efficiently and in order to defend themselves against other animals (including other humans).
Over thousands of generations, the need to apply physical force more efficiently drove changes, through natural selection, in the shape and design of their hands.
Ultimately the process resulted in hands that could make sophisticated tools, weapons and other artefacts – and, in time, that physical ability to make things in turn allowed and drove additional evolutionary changes in their brains to enable them to even more effectively envisage and invent the ever more sophisticated items they needed to help them survive and flourish. The rest was history, as they say.
Just how intellectually able they had become by 500,000BC has been revealed by a recent experiment at Emory University in Atlanta, Georgia. Using the Boxgrove hand-axes as exemplars, 20 students and others were tasked with learning the tool-making skills to replicate them. It took, on average, 200-250 hours for each modern novice toolmaker to learn how to do it.
The University of Kent’s research by Dr Key and his colleague Christopher Dunmore on prehistoric hand dexterity has just been published online in the academic journal, PeerJ.
