Photograph: Bill Arnold “Allan’s Boys”
DAY
5
EVOLUTIONARY STORY: In the Water
The evolutionary story of the human species begins in the water. In that fluid environment, diverse forms of life emerged. Plant life preceded animal life as a producer of oxygen and a primary food source. About 3.5 billion years ago, according to available fossil records, photosynthetic bacteria and blue-green algae formed in the primordial seas demonstrating the basic characteristics of life: the ability to reproduce, metabolize, and respond to change. By 1.5 billion years ago, the first single-celled organisms appeared with the capacity to reproduce sexually (mixing of the DNA of two cells) instead of by cell division (division of one cell into two identical parts) thus increasing the potential for diversification. Around 600 million years ago, we find evidence of a full range of multicellular life with unique body structures: primitive forms such as sponges and jellyfish; shelled mollusks including snails and clams; starfish and sea cucumbers with radial (five fold) symmetry; elongated or segmented forms of worms; joint-limbed creatures whose contemporary ocean relatives include lobsters, shrimp and crabs; and the more advanced creatures with backbones such as cartilaginous sharks or bony fishes. We can experience a similar diversity today by observing the multiplicity of underwater life present in a coral reef!
Throughout the evolutionary story, species (populations of individuals which habitually mate with one another) become extinct, remain constant, or adapt in a process called natural selection. Change occurs by random genetic mutation, followed by successful reproduction. Some creatures evolve characteristics which allow survival when new conditions such as increased population or climatic shifts force a change. One example is the freshwater lungfish, which evolved internal air bladders and muscular lobes on its fins. These preadaptive structures eventually facilitated the species in walking on land. Some forms, such as the shark, are so successful that they have remained almost the same for millions of years. Others, like the dinosaur, dominated the land for 150 million years before they became extinct. The human species, Homo sapiens, has walked the earth for a mere two million years and continues to evolve.
We will look at three types of body symmetry and their relationship to human movement patterns. Asymmetry is characterized by a single-celled organism, like an amoeba, in which all components of the membrane are of equal importance. Exchange of nutrients and waste materials takes place through this semipermeable membrane, and the organism moves as its protoplasm shifts in relation to the environment. A sponge, a loosely organized collection of single cells, provides a multicelled example of asymmetry. (If you put a sponge through a sieve, the cells will reassemble in their original form.) Radial symmetry brings the mouth and gut to the center, with appendages radiating from this core. The starfish, as a lasting example, walks on the ocean floor to find and devour its food. Bilateral symmetry differentiates a “head” and a “tail” end with paired body parts. The mouth and primary sense organs gravitate towards the head, and appendages for propulsion and elimination towards the tail. In some species, like the shark, a cartilaginous “spine” links head and tail for stability and directionality, with fins used for buoyancy (if a shark stops swimming, it sinks), but in others such as the bony fishes, a skeleton and paired appendages develop for additional stability and mobility in the water (with internal air bladders providing buoyancy). The sea squirt demonstrates the transition from invertebrate (without a spine) to vertebrate form. The adult has radial symmetry and lives planted in the ocean floor, but the juvenile form has a notocord (primitive spine) and swims like a tiny fish, with bilateral symmetry, before changing into its less mobile adult form. Bilateral symmetry and a bony skeleton provide efficiency for basic survival needs such as going towards food, escaping from enemies, pursuing a mate, and exploring the environment, and are useful components in the transition to land. Although our discussion is primarily anthrocentric – focused on the human species – ninety-five per cent of the animals on earth today have no backbone!
Layers
I was backpacking into the Grand Canyon from the north rim. Our descent into the deepest cleft in the earth’s surface took three days. In our group was a geologist who loved reading history through the layers of stone. We began by looking for cockleshells and other fossils in the white bed of Kaibob limestone crumbling under our feet – an estimated 225 million years in the making. On the first night, we camped facing the smooth Redwall – limestone 300 million years old; on the second night we slept at the site of an old Anasazi ruin, facing what was called the Great Unconformity – an eroded era of ancient rock, formed before life was present on the earth, now missing from the geological “book” of the canyon walls. On the third day, as we lay in the hot sun on the banks of the Colorado River, my friend pointed to the black metamorphic rock which lined the edge of the water, and said, “That’s Vishnu shist. Two billion years.” Then he added, “Now that’s old.”
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During a conversation with a college biology professor, I said, “I encourage students to study the human body.” He responded, “I remind them that humans aren’t the only species on earth.”
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I was traveling in East Africa. We were in Amboselli National Park in Kenya, on a game drive at dusk. We had stopped to watch elephants walking parallel to us in the trees. As if on cue, the elephants turned and made a path directly towards our van. They formed a straight line, with the mother and father on either end protecting two babies of different ages between them. As they progressed systematically, we backed up our van, and they passed a few feet in front of us without ever breaking stride. Their eyes looked ancient, the skin sagged off huge bodies, and the trunks uprooted turf and searched for minerals in the soil and rock. They had been around for a long time. I imagined them saying, “Move over.”
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We were in Tanzania, gazing from a dusty overlook towards Olduvai Gorge. We were amidst a small gathering of tourists from around the world all wearing safari hats and sipping sodas. It was here that noted Kenyan paleoanthropologists Mary and L.S.B. Leakey discovered fossil hominids – an Australopithecine skull, “Zinjanthropus” in 1959, and fragments from Homo habilis in 1961 – dated 1-2 million years old. Nearby, Mary found footprints preserved in volcanic ash determining that as early as 3.7 million years ago, upright, bipedal forms of the species Homo erectus lived in Eastern Africa. We listened to our guide translate this earliest history of the human heritage into various languages. There was a sense of Africa as common origin.
Just as we carry the saline solution of the ocean in our blood, our structure holds the possibilities of earlier forms of body symmetry. We can move asymmetrically, as in our early morning yawning and stretching, allowing our skin and proprioceptors to be our primary sense organs before the cerebral cortex (the newest portion of the brain) directs our awareness. Contact Improvisation and Authentic Movement are techniques which focus on stimulating and responding to all surfaces and structures of the body equally. We can move in radial symmetry, like the starfish, or the Leonardo da Vinci drawing of “geometric man” with body parts radiating from the solar plexus. Cartwheels demonstrate this symmetry. Martial arts also organize movement around the “belly brain” (autonomic nervous system) focusing on the tant’ien (in tai chi) or the hara (in karate) for “centered” energy. We can move in bilateral symmetry, undulating our segmented spine like fishes or whales. Kundalini yoga and many primitive dance forms use this powerful source of head to tail integration. Although our outer form is organized bilaterally, many of our internal organs (such
