His hands are like antennae, gathering information as they flick outward, surveying the rock for cracks, grooves, bowls, nubbins, knobs, edges and ledges, converting all of it into a road map etched into his mind. --Karl Greenfeld (2001:60) on Erik Weihenmayer, 33, the first blind climber to scale Mount Everest (see below, Anatomy)
Her hand was small and had shape, not the usual bony garden tool you see on women nowadays. --Philip Marlowe, describing Eddie Mars' wife (The Big Sleep, 1939:191)
His hands rose, fluttered like wounded birds a few inches above the surface of his desk, slowly came back to a landing. --George C. Chesbro, Shadow of a Broken Man (1977:40)
Smart parts. 1. The terminal end organs below the forearms, used to grasp and gesture. 2. The most expressive parts of the human body.
Usage: Their combined verbal and nonverbal IQs make hands our most expressive body parts. Hands have more to say even than faces, for not only do fingers show emotion, depict ideas, and point to butterflies on the wing--they can also read Braille, speak in sign languages, and write poetry. Our hands are such incredibly gifted communicators that they always bear watching.
Observation. So connected are hands to our nervous system that we rarely keep them still. Indeed, the First Law of Nonverbal Dynamics would be, "A hand tends to stay in motion even while at rest." When a hand is not moving or handling an object, it is busy scratching, holding, or massaging its partner. This peculiar tendency of the digits to fuss and fidget intensified as our fingers became major tools used to explore and shape the material world. The more gifted they became, the more we waved them about as sensory feelers.
Anatomy. Hands are the tactile antennae we throw out to assay our material world and palpate its moods. Most of the 20 kinds of nerve fiber in each hand fire off simultaneously, sending orders to muscles and glands--or receiving tactile, motion, and position information from sense organs embedded in tendons, muscles, and skin (Amato 1992). With a total of 100 bones, muscles, joints, and types of nerve, our hand is uniquely crafted to shape thousands of signs. Watching a hand move is rather like peering into the brain itself.
Cave art. Stenciled images of human hands are "common" and "sometimes dominate" areas of Ice-Age caves (dating to between 35,000 and 20,000 years ago; Scarre 1993:59). In France's Gargas cave, hands are depicted with missing fingers or finger segments. "It is unclear whether the joints had actually been lost through frostbite or some other condition, or whether the fingers were bent in some kind of signaling system" (Scarre 1993:59; see below, Neuro-notes II).
Evolution. The 27 bones, 33 muscles and 20 joints of our hand originated ca. 400 m.y.a. from the lobe fins of early fishes known as rhipidistians. Primeval "swim fins" helped our aquatic ancestors paddle through Devonian seas in search of food and mates. In amphibians, forelimbs evolved as weight-bearing platforms for walking on land. In primates, hands were singled out for upgrade as tactile antennae or "feelers." Today (unlike flippers, claws, and hooves), fingers link to intellectual modules and emotion centers of the brain. Not only can we thread a needle, e.g., we can also pantomime the act of threading with our fingertips (see MIME CUE)--or reward a child's successful threading with a gentle pat. There is no better organ than a hand for gauging unspoken thoughts, attitudes, and moods.
Embryology. Hands are visible as fleshy paddles on limb buds of the human fetus until the 6th week of life, when digital rays form separate fingers through a process of programmed cell death. Soon after, hands and arms make coordinated paddling movements in mother's amniotic fluid. Placed in water shortly after birth, babies can swim, as paleocircuits of theaquatic brain & spinal cord prompt newborns to kick with their feet and paddle with their hands.
Infancy. Babies are born with the primate ability to grasp objects tightly in a climbing-related power grip. Later, they instinctively reach for items placed in front of them. Between 1-1/2 and 3 months, reflexive grasping is replaced by an ability to hold-on by choice. Voluntary reaching appears during the 4th and 5th months of age, and coordinated sequences of reaching, grasping, and handling objects are seen by 3-to-6 months, as fingertips and palms explore the textures, shapes, warmth, wetness, and dryness of Nonverbal World (Chase and Rubin 1979).
Early signs. By 5 months, as a prelude to more expressive mime cues, babies posture with arms and hands as if anticipating the size and hardness (or softness) of objects in theirreach space (Chase and Rubin 1979). Between 6 and 9 months, infants learn to grasp food items between the thumbs and outer sides of their index fingers, in an apelike precursor of the precision grip. At this time, babies also pull, pound, rub, shake, push, twist, and creatively manipulate objects to determine their "look and feel" (Chase and Rubin 1979).
Later signs. Eventually, a baby's hands experiment not only with objects themselves but with component parts, as if curious to learn more about relationships and about how things fit together (Chase and Rubin 1979). At one year, infants grasp objects between the tactile pads of thumb and index fingers, in a mature, distinctively human precision grip. Pointingwith an extended index finger also begins at 12 months, as babies use the cue to refer to novel sights and sounds--and speak their first words.
Neuro-notes I. Our brain devotes an unusually large part of its surface area to hands and fingers (see HOMUNCULUS). In the mind's eye, as a result a. of the generous space they occupy on the sensory and motor strips of our neocortex, and b. of the older paleocircuits linking them to emotional and groomingcenters of the mammalian brain, almost anything a hand does holds potential as a sign. Today, our hands are fiber-linked to an array of sensory, motor, and association areas of the forebrain, midbrain, and cerebellum, which lay the groundwork for nonverbal learning, manual sign language, computerkeyboard fluency, and the ability to make tools of stone, silicon, and steel.
Neuro-notes II. We respond to hands and their gestures with an extreme alertness because specialized nerve cells in the lower temporal lobe respond exclusively to hand positions and shapes (Kandel et al. 1991:458-59). "For cells that respond to a hand, the individual fingers are a particularly critical visual feature" (Kandel et al. 1991:459).
Neuro-notes III. Mirror neurons: We have known for over a decade that the human mirror neuron system (hMNS) responds to seeing someone make reaching movements toward an object, such as a peanut or a grape, with the intention to pick it up. Research reported in 2007 shows that the hMNS also responds to speaking gestures, such as pointing and beckoning, and even to the North American "OK" sign (Montgomery et al. 2007).
Neuro-notes IV. Why we gesture with our hands as we speak: I've always wondered about this. Now we have the answer. Source: Bass, A. H and B. Chagnaud (2012) Shared developmental and evolutionary origins of neural basis of vocal-acoustic and pectoral-gestural signaling. Proceedings of the National Academy of Sciences (USA):
"Acoustic signaling behaviors are widespread among bony vertebrates, which include the majority of living fishes and tetrapods. Developmental studies in sound-producing fishes and tetrapods indicate that central pattern generating networks dedicated to vocalization originate from the same caudal hindbrain rhombomere (rh) 8-spinal compartment. Together, the evidence suggests that vocalization and its morphophysiological basis, including mechanisms of vocal-respiratory coupling that are widespread among tetrapods, are ancestral characters for bony vertebrates. Premotor-motor circuitry for pectoral appendages that function in locomotion and acoustic signaling develops in the same rh8-spinal compartment. Hence, vocal and pectoral phenotypes in fishes share both developmental origins and roles in acoustic communication. These findings lead to the proposal that the coupling of more highly derived vocal and pectoral mechanisms among tetrapods, including those adapted for nonvocal acoustic and gestural signaling, originated in fishes. Comparative studies further show that rh8 premotor populations have distinct neurophysiological properties coding for equally distinct behavioral attributes such as call duration. We conclude that neural network innovations in the spatiotemporal patterning of vocal and pectoral mechanisms of social communication, including forelimb gestural signaling, have their evolutionary origins in the caudal hindbrain of fishes."
Neuro-notes V. Muscles that today move the human larynx and pectoral girdle evolved from hypobranchial muscles that originally opened the mouths and gill openings of ancient fishes. Paleocircuits that mediate our laryngeal and pectoral movements are connected in the posterior hindbrain and anterior spinal cord (Bass and Chagnaud 2013). The sonic properties of these bodily regions (vocalizing and pectoral vibration, respectively) were recruited for social signaling in a watery world. The sounds were basically "assertion displays" used to announce a sender's physical presence, often in courtship, to attract mates or repel rivals. Controlled by branchial muscles, these body parts were more easily aroused to produce vibratory sounds than were parts controlled by other than branchial nerves. In primates, the pectoral movements became visual signals, which in humans are called gestures.
Photo of replica statue of "David" (Caesars Palace, Las Vegas, Nevada, USA) by Doreen K. Givens (copyright 2009)