Evolutionary Information

Do you wake up sensing vastness?

Compared to the Hindu and Buddhist cultures, the mythic cosmologies of the West lack a sense of vastness until our sciences supplied them. In the East images like Indra’s Net have been used to illustrate existence by likening it to a vast net of diamonds, all reflecting one another just as mirrors in a fun house, where every diamond is a whole universe unto itself. It is a common eastern understanding of existence that whole universes are endlessly born and die in vast cosmological cycles. When your eyes blinked open this morning, according to this way of interpreting the experience of being alive and awake, surrounded by mystery, you found yourself again consciously aware in the midst of this vastness of both time and space. The vastness exceeds human thought and imagination in a way not that dissimilar to the vastness we in the West can appropriate by studying astronomy and the ecology of deep time.

I don’t think we properly appreciate the preciousness of what we are putting at risk. A truly heart-felt gratitude for the biosphere and all it offers us requires a sense of just how vast the biological deep time of our planetary evolution actually is. It is important to try and understand viscerally that of the approximately 4 billion years in which life has been evolving, approximately 3 billion of those years were taken up with the evolution of microorganisms, which are still by far the most dominant life form on the planet. It is important to try and understand viscerally that more than 99% of all species that have ever lived are currently extinct, that all the overwhelmingly diverse biological forms we see about us today represent nothing more than the slightest tip of the iceberg.

I see the study of life in the fields of evolution and ecology somewhat like the symbols in the Tarot deck. All the symbols are there and the terms are accurate but like the neophytes yet to be initiated we are prone to misunderstand what they mean. We are blind to the real implications of these symbol systems, these sciences, for our lives. Contemplation is our initiatory methodology by which the understandings of the adepts can be acquired. Less poetically: if you really get it, you live it. Climate change is not just a political football and green marketing opportunities. The eco-crises are not just for our entertainment. Something much more powerful is going on here for our species, something involving planet wide forces across deep time and its dream time. Dream time, as I understand it, is like Jung’s collective unconscious or our shared consciousness, or the summation of all that is conscious.  Something like this exists emergent among us since human consciousness is not separate and isolated from the rest of life’s awareness in which it is rooted. In order to tune into that, the small worldview of consumerism needs to be left far, far behind. The heart is noble, yet it remains a choice for each and every one of us whether or not to heed the wakeup call in the age of limits. With evolution and ecology we are in the temple’s Holy of Holies where it would be wise to take off our shoes, for we are treading on sacred ground.

We have been looking into the ins and outs of evolutionary mechanisms the past few weeks. The recommended contemplations have been around the extent of evolution’s reach, its all-encompassing nature. This has been offered to try and provide us with some felt sense of just how vast the living network of our planetary biosphere really is. Earlier we looked at how easy it is for our minds to form abstractions and generalizations which while helpful in some contexts also blind us to the actual. In nature we find everything is unique and at least a little bit different than its neighbor; every blade of grass, every leaf, every mouse and every elephant. These are the differences that are all important from the evolutionary perspective. To really appreciate what is involved requires, it seems to me, a concomitant appreciation of the vastness of the forms and forces involved. Otherwise our understanding is threatened by an overly simple generalization of the subject which leaves the impression of the biosphere as an unthinking machine.

The metaphor of the biosphere as a machine is a popular one in our culture; it all has to exist for some purpose like a machine and was designed for achieving that purpose like a machine and uses energy to engage flows of inputs to produce transformed outputs like a machine. Enamored as we are with gadgets and machines, when we encounter something like the DNA molecule our default interpretive context for it naturally involves machine-like characteristics. We see abstractions and generalizations where in fact the products are all concrete and specific; there is no turtle, there is only this turtle here, and that turtle over there, indeed it is specific, individual turtles all the way down. Because we see abstractions instead of the particulars which are the abstractions referents these machine like characteristics seem dominant among the evolutionary and ecological processes.

That organisms are the antithesis of machines is of course a bit of a problem for these models. Machines do not learn nor reproduce yet these are the very characteristics defining evolution. Machines do not grow and move through lifecycle stages yet this is the very characteristics defining evolutionary development, evo-devo. With these antimonies in mind what, we might ask, is the reason a machine-like model has been dominant in the biological fields? The answer is doubtless many faceted and complex. The cynic will point out how a model of nature as machine holds out the promise of mankind one day completely understanding and controlling it. Knowledge is power in this model and a machine is theoretically transparent to the understanding. There is some truth in that analysis and it is worth developing. However, there is another similarity I propose is more relevant, namely computing. To appreciate it will require a bit of history.

Darwin’s 1859 publication came on the heels of what historians refer to as the industrial revolution. The discovery of evolution by natural selection occurred at a time and place where applying scientific insight through the technological design of machinery had thoroughly transformed individual lives, societies and both the urban and rural environments in which they found themselves. When Origin of the Species was published there was no clear understanding of how descent with modification happened in living things, only that undeniably it did. By the time the actual mechanism of genetic inheritance was discovered and the structure of the DNA molecule was mapped in the 1950s, the cutting edge of technological development was learning how to produce computers – information processing machines. Here is where I see a metaphorical similarity between machine and DNA processes. The amino acid pairs might be similar to Lego-like building blocks familiar to numerous technologies but it is with the information processing machines that we encounter an almost uncanny alignment of biology and engineering. From the bacterial chemical exchanges to the pulse patterns of the nerve cord we find systems that embody information and assist its exchange have been favored by evolution throughout the animal kingdom.

The evolution of eyes, wings, lungs, hands, skin, skeletal joints, and all the other features of animal physiology are fascinating and full of lessons but I want to focus our attention around the evolution of the nervous system, the information carrying stratum par excellence.PurkinjeCellThe basis of the nervous system is the neuron which is typically formed with a set of branches at one end called its dendrites, a cell body and a single axon. The dendrite tree extends a few hundred micrometers as it branches, whereas the axon of a single neuron cell can extend up to a meter in the human body. There are families of neurons specialized as sensory neurons, motor neurons and interneurons or those which connect neurons together as we find particularly in the brain and spinal cord.

The neuron is a cell specialized to transmit an action potential. The evolution of the action potential occurred in the single celled eukaryotes as they found a quick electrical pulse along their membrane a useful way to activate biochemical pathways within the cell. The details of the voltage gated ion channels which produce the action potential need not concern us here, though it is helpful to know there are two main types. In one a sodium channel is used and the action potential lasts under a millisecond and in the second a calcium channel is used and its action potentials can last 100 milliseconds or even longer. These nerve impulses or spikes travel the length of the neuron’s single axon. The interneurons typically respond to the spike by releasing neurotransmitters which in turn excite neighboring neuron’s dendrites. In this way a signal is sent across the synaptic gap and communication occurs.

The Jellyfish and similar animals use a set of neuron cells structured as a web, a nerve net. With this relatively primitive structure they are able to absorb sensory inputs, process those signals and use them to activate muscles and other physiological processes.  Already in the nerve net the fundamental capability of the nervous system is beautifully illustrated. They provide a window on the world through their ability to sense visual, chemical, tactile, taste and odor signals. There is something very magical about how the senses bridge the inner and outer worlds. These nerve nets also provide the orchestration required for numerous life support systems, from muscle contractions to the production of insulin.

Tinkering with the nerve net over deep time resulted in the development of the nerve cord, what in humans is expressed as the spinal column. With the introduction of a centralizing feature body forms take on the bilateral symmetry that is found extensively throughout the animal kingdom. The phenotype in which the left and right sides mirror each other is constructed around a tube running mouth to anus and a nerve cord with a ganglion or enlargement at each of the body segments.

Bilateral animals can be divided into two camps depending on how this nerve cord is positioned during the early stages of their embryonic development. Early evo-devo expressing the DNA information will position the nerve cord either on the front or backside of the trunk. Insects for example have the nerve cord running along the ventral midline whereas vertebrates have it running along the dorsal midline. Basically the segmented body arrangement is flipped over so where one has the cord running along the back, the other has it running along the belly. There are numerous other features of these two groups’ phenotypes that are also inverted.

HoxGeneRemember the body segments from the fruit fly we saw in this picture when we were discussing evo-devo? The segmented body plan along the trunk of an animal is laid out in the nerve cord through a series of narrow bands. The body innervation pattern follows those segmentations. It is not at all dissimilar to the classic image of the yogic chakra system with the chakras corresponding to the major ganglions.

nadisThe top three segments of the segmented body plan laid out in the nerve cord are what become in modern humans the forebrain, midbrain and hindbrain. We will begin looking into that a bit next week.

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