Body movement. 1. A manner of grasping an object between the opposed tactile pads of the thumb and fingertips. 2. A digital manipulation of fine motor control used, e.g., to write with a pencil, thread a needle, or change a lightbulb.
Archaeology. The earliest evidence for use of the precision grip to produce symbolic art is an engraved, flat piece of shale-like ochre (red hematite [artifact no. SAM-AA 8937]) from Blombos Cave, South Africa. The etched, angular geometric pattern indicates that its maker could form abstract ideas over 70,000 years ago, according to Dr. Christopher Henshilwood of the South African Museum in Cape Town.
Culture. When asking a question, an Italian may hand purse (i.e., bring the tactile pads of the thumb and fingers together, and oscillate the palm-upward hand, up and down, by alternately flexing and extending the wrist). "Essentially this is a request for clarity. It is a 'precision posture' of the hand that says 'I want precise information'" (Morris 1994:115).
Evolution. The precision grip originated as an adaptation for primate grooming and finger-feeding. By ca. 40 m.y.a., the higher primates could oppose the thumb pad to the side of the second digit to clean insects from fur, pluck berries from bushes, and bring food to the mouth. By ca. 2.6 m.y.a., hominids such as Homo habilis used an improved precision grip (i.e., opposed the thumb against the digital pads themselves) to make crude Oldowan stone tools. By ca. 100,000 years ago, early humans used the fully modern precision grip, just as it is employed today (Trinkaus 1992). As a precision cue, precise opposition of the tactile pads suggests that dexterous brain modules have shifted into gear for activities such as problem-solving, planning, tool usage, and thoughtful design.
RESEARCH REPORTS: 1. "In particular, the way one holds a pen (and other, similar objects) is known as the precision grip--and even our closest primate relatives cannot manipulate objects with such delicacy and skill" (Staski and Marks 1992:190). 2. "Fine manipulative skills and a dependence on tools to exploit resources are hallmarks of the human species" (Trinkaus 1992:346). 3. The tactile pads of Homo habilis are as highly developed as those of modern human beings (Wills 1993).
Neuro-notes. The precision grip reflects an incredibly complex neural-wiring plan which has made our fingers intellectual "smart parts" of the highest order. We are able to thread a needle (or to pantomime the act) through intricate sequences of finger movements controlled by theprefrontal neocortex, working in tandem with two areas of the parietal neocortex: a. the supramarginal gyrus (Brodmann's area 39), and b.the angular gyrus (Brodmann's area 40). On the right side of the brain, these areas have specialized in order to process spatial information, while on the left side, to process speech. The prefrontal neocortex has improved our ability to sequence nonverbal hand and finger movements, while the parietal neocortex has bettered our ability to locate objects in space, to decode complex gestures, and to recognize objects placed in our hands by touch alone (i.e., without seeing them).
See also HANDS.