to the trees and adapted to a posture of hunkering on branches. In this squatting position, feet grasped the branch and legs were folded (flexed) to the belly, leaving the hands or forepaws free for eating, grooming, and gesturing. The hunkering posture encouraged structural changes in the body: the heel bone (calcaneus) migrated to the back surface opposite the toes, an arch was formed by the connecting bones of the foot, and the pelvis shortened to allow the femurs to fold in squatting position.
The new use of the hands also developed a cross-pattern of thumb opposite fingers for grasping. Picking the plentiful nuts and flowers of the evolving seed-bearing plants (angiosperms) required coordination of eyes with hands. Our ape ancestors began hanging from their arms and swinging from limb to limb through the treetops, called brachiation. This allowed extension of hip and shoulder joints, repositioning of the shoulder bones (scapulae) to the back surface of the body for hanging and lateral reaching, contralateral rotation at the waist necessary for swinging, and elongation of the spinal curves. The curve in the lower back (our lumbar spine) formed last, after the arboreal swinger returned to the ground as a semi-quadruped. The transition then to upright posture was accompanied by the anterior (forward) curve of the lumbar segment. These characteristics prepared the way for two-footed, vertical posture: a bipedal stance.
Multidimensional agility of body and brain evolved simultaneously in our structure. Without moving our feet, humans can reach in front, to the sides, or behind. This three-dimensional rotation of the spine and hips permitted quick response in any direction. The free-swinging pelvis held the organs in a lightweight bowl and allowed mobility (unlike our close relative, the gorilla, who evolved from a common ancestor but whose large pelvis restricts vertical extension and whose knuckle walking and vegetarian diet encourage a more passive existence). The use of tools and the development of family groups increased the need for articulation and communication. In essence, we could stand, move three-dimensionally, manipulate our environment, and articulate with gesture and sound. Neurological adaptability increased our ancestors’ potential for survival.1
Nancy Stark Smith and Andrew Harwood. Photograph by Bill Arnold.
STANDING UP
“The Small Dance” is a movement exercise developed by dancer Steve Paxton. You close your eyes and stand with your weight balanced in vertical alignment. The intent is to notice all that is happening inside in what we call stillness: the myriad shifts, micromovements, rhythms, and idiosyncrasies that happen moment by moment. The small dance is our dialogue with gravity and the dynamics of the earth. As we open our eyes, we can remain aware of this conversation and “listen in” throughout the day as we stand in a line, talk on the phone, or walk through the woods.
Three body weights with horizontal diaphragms.
The basic characteristic of our species, Homo sapiens (wise man), is the increased capacity of the brain. As all of our systems developed simultaneously with our skeletal-muscular changes, our physiological capabilities were matched by our capacity for three-dimensional thought in the past, present, and future. (Imagine our brain in the body of a horse.) We are able to reflect on where we have been, contemplate where we are, and plan where we are going. This capacity for reflection, planning, and manipulation of our environment brings the responsibility of choice. Our ability to plan and to shape our environment makes us responsible for what we create and for how we choose to live in that creation. As we reflect on the precarious stance of the human—center of gravity vertically balanced over the length of our feet, constantly falling, essentially alert—we recognize that responsiveness and responsibility underlie our relationship to the earth.
The evolutionary progression to verticality offered additional implications for our bodies. As three primary tissue layers differentiate in the developing embryo, the ectoderm becomes the skin and nervous system, responsible for communication; the mesoderm becomes the skeleton, muscle, and connective tissue, responsible for support; and the endoderm becomes the organs, essential for breathing, digestion, and reproduction. In a simplified drawing of the bilateral fish body, the brain and nervous system are on the top for perception and communication, the segmented skeleton is next for support, and the organs hang by connective tissue (mesentery) off the spine for metabolism and reproduction, creating an efficient layering in horizontal alignment.
Shifting these layers into human verticality alters our dialogue with gravity. What used to be horizontal support (i.e., our backs) is now a vertical series of balanced curves. What used to hang (our organs) is now stacked. What used to communicate (our spinal cord and brain) is now an axis integrating head and tail, sky and earth. Our genitals, belly, breasts, and face, once protected by their horizontal relationship with the earth, are exposed, creating a vulnerable but dynamic and expressive body. Communication within community is now face to face, belly to belly, responding to information from all the senses.
In the core of the body, several musculotendinous partitions, called diaphragms offer horizontal support in vertical alignment. Beginning with the skull, the cranial diaphragm creates a sling for the brain, cushioning it from impact as we walk. In the neck, a vocal diaphragm supports the structures for voice. In the torso, the thoracic diaphragm creates a mobile rhythmic floor for the lungs and heart and massages the organs during the process of breathing. The pelvic bowl includes a fibrous pelvic floor, offering resilient support for digestive and reproductive viscera. Even the arch in the foot, a webbing of muscles, tendons, and ligaments below the bony bridge of tarsal and metatarsal bones, creates a horizontal diaphragm, offering spring and shock absorption for our striding gait.
Along with the vertical axis supporting bipedal directionality, human structure includes three globes (skull, ribs, and pelvis) and four rotary joints of shoulders and hips through which we occupy spherical space. Although we often think of ourselves as flat and two-dimensional, as reflected in photographs, mirrors, and on television or computer screens, we have sculpted fullness. Curves and angles give force and agility to the body, connecting us with forms beyond and inside us. Nerves inform us about the landscape, interior and exterior. The human form inhabits spherical space, as multidimensional and diverse as our curiosity allows, inviting investigation and discovery.
In an efficient vertical stance, the skull, thorax, and pelvis are balanced around an imaginary plumb line or vertical axis. If we draw three ovals, representing these three body weights, and connect them with a vertical plumb from the top of the skull to the feet, we have a diagram of postural alignment in the body. The front is also called the anterior or ventral surface, and the back is the posterior or dorsal surface, as we look at the body from a lateral, or side, view. The three body weights connect with a series of reversing curves: anterior at the neck, posterior at the ribs, anterior at the lower back, posterior at the pelvis (sacrum), and anterior at the small curve of the coccyx—the ancestral tail—connecting to the front surface of the body through the webbing of the pelvic floor. Each spinal curve touches but does not pass the plumb line in front. The center of gravity lies in the area behind the belly button at the front of the (lumbar) spine, intersecting the plumb line. To locate the center of gravity (c.g.) in your own body, imagine the point created by the intersection of the three primary planes of the body dividing you equally by weight: front to back, side to side, top to bottom. The c.g. is in front of the fourth or fifth lumbar vertebra in most bodies.
Additional bony landmarks for efficient postural alignment include the two “feet” of the skull (occipital condyles) as they pass the entire weight of the structure (some 13–20 pounds) to the first vertebra of the spine (the atlas). The ischial tuberosities (sit bones) are the two “feet” of the pelvis, which point straight down in efficient postural alignment, standing or seated. Balanced alignment of the pelvic bowl requires that the front rim of the pelvis (pubic bone) support the organs. Imagine that the entire front surface of the body—pubic bone, belly button, sternum, and nose—has an upward energy flow, and the entire back surface of the body—back of skull, back of ribs, and back of sacrum—has a downward energy flow (like a waterfall), creating a cyclical pattern throughout the structure. The two body surfaces—anterior and posterior—complement and run parallel