6 March 2001
New Ideas About Technology And Evolution
by Kate Melville
What distinguished Neanderthals and near-modern humans from their predecessors 300,000 years ago, it is believed, was their ability to make and use complex tools, but there is no consensus among experts about how this dazzling leap in technology influenced human evolution. In the March 2 issue of the journal Science, paleoanthropologist Stanley Ambrose challenges conventional wisdom about Paleolithic technology and hammers out a set of new hypotheses about our evolutionary odyssey.
In his article, "Paleolithic Technology and Human Evolution," Ambrose offers a comprehensive review of the evidence for tool-making and the evolution of hands and brains as a foundation upon which to propose ideas about the co-evolution of our ancestors' technology, hands, brains and language. Complex tool-making, which required fine motor skills, problem-solving and task planning, he argues, may have influenced the evolution of the frontal lobe, and co-evolved with the gift of grammatical language 300,000 years ago.
Bimanual tool use was the first major breakthrough.
The ability to steady an object with one hand - usually the left - while working it with a tool held in the other, led to preferential handedness. Habitual tool-making and use "may have led to lateralization of brain function and set the stage for the evolution of language," Ambrose said. The chimpanzee has poor bimanual coordination, no overall preference for right-handedness, weak precision grip and limited wrist mobility and thumb strength - anatomical features critical for making and using complex tools.
Ambrose, a professor of anthropology at the University of Illinois, traces early man's ability to accomplish "complex fine motor control (FMC) non-repetitive action sequences involved with making complex tools" to the precursor of Broca's area in the modern brain, which controls the oro-facial FMC, and thus, language - also a series of FMC non-repetitive action sequences. Broca's area is "adjacent to and probably has a common developmental origin with the hand's FMC area," Ambrose said.
"Grammatical language, planning complex tasks and composite tool use were closely related," he said.
"The ordering of sequences and the hierarchical assembly of the same components into different configurations makes tools of different functions and makes phrases of different meanings."
Gathering the components for composite tools (stone inserts, handles, binding materials) requires planning and coordinating different tasks before a tool is assembled. "The part of the frontal lobe that we now use for planning complex tasks may have coevolved with composite tool-making around 300,000 years ago."
As makers of single-component tools, we progressed at a remarkably slow pace between 2.5 and 0.3 million years ago. But "with the appearance of composite tools, near-modern brain size, anatomy and perhaps of grammatical language 300,000 years ago, the pace quickened exponentially. We became long-range planners and grammatical speakers. Composite tools made us what we are today."