Three Big Bangs Page 8
Plants develop steadily on the land masses, with species turnover resulting in increased diversity. Andrew H. Knoll graphs (fig. 2.4) this record for local ecosystems over evolutionary time. In the Paleozoic there is a general rise, and after that a plateau. “The history of diversity within floras from subtropical to tropical mesic floodplains is marked by several periods of rapid increase separated by extended periods of more or less unchanging taxonomic richness.” After the mid-Mesozoic, with the rise of the angiosperms (flowering plants), there is a steady climb in regional floras. Knoll concludes “that species numbers within subtropical to tropical communities have been rising continually since the Cretaceous and that a plateau has yet to be established” (Knoll 1986:140, 132; Wilson 1992:195).
In the composition of the floras and faunas, certain forms can later be less numerous than before; but, climatic conditions permitting, overall biodiversity gradually and sometimes rather spectacularly rises, as seen in graphs illustrating the composition of vascular plants (fig. 2.5, Niklas 1986) and vertebrate orders (fig. 2.6; Niklas 1986). Here too the later-coming forms are often more complex than the earlier ones they replace. Mammals with their warm blood and higher energy requirements develop metabolisms and behavioral skills not present in cold-blooded reptiles and amphibians. Angiosperms advance over, and may displace, gymnosperms. Fortunately for overall biodiversity, these earlier groups, in reduced numbers (and with species turnover), often continue to enrich present faunas and floras.
Figure 2.4 Average number of plant species found in local floras (Wilson 1992, adapted from Knoll 1986)
Figure 2.5 Species diversity changes in vascular plants (Niklas 1986)
Figure 2.6 Changes in the composition of vertebrate orders and numbers of insect genera (Niklas 1986)
Consider a series of graphs in land plant diversification (Niklas, Tiffney, and Knoll 1985:193, 107, 112). The first graph (fig. 2.7), Silurian through Devonian times, escalates up, then down. The second (fig. 2.8), Carboniferous to Lower Cretaceous, shows escalation, then stagnation in total numbers, but with erratic shifts in the kinds of plants—ferns, lycopods, cycads, conifers. The third (fig 2.9), Lower Cretaceous to recent times, shows steady rise, dominated by angiosperms, and older forms declining.
Figure 2.7 Changes in species diversity in Silurian-Devonian times (Niklas, Tiffney, and Knoll 1985)
Figure 2.8 Changes in species diversity in Carboniferous-Lower Cretaceous times (Niklas, Tiffney, and Knoll 1985)
Figure 2.9 Changes in species diversity in Cretaceous-Tertiary times (Niklas, Tiffney, and Knoll 1985)
But if we watch the scales of the graphs and align them for an overall record, the result is a rather striking graph of exploding plant life, with overall increases in biodiversity, as much because of as despite fluctuations in kinds (fig. 2.10). (Subgroups are placed differently in the three graphs.)
Turning to animals, consider a graph of increasing diversity of orders in vertebrates (fig. 2.11, Padian and Clemens 1985:50). Again the graph, in the first half, has a jagged look, but the overall impression is strikingly of increasing vertebrate diversity over geological time.
E. C. Pielou concludes a long study of diversity: “Thus worldwide faunal diversification has increased since life first appeared in a somewhat stepwise fashion, through the development and exploitation of adaptations permitting a succession of new modes of life” (Pielou 1975:149). Life appears in the seas, moves onto the land, then into the skies. Terrestrial communities developed from the Silurian onward. In the Tertiary there was a marked increase in diversity due to the rise of warm-blooded vertebrates (mammals and birds), more than making up for the decrease in reptiles and amphibians. When vertebrates took to the air, there was introduced an entirely new mode of life.
There were setbacks, notably in the Permian-Triassic and again in the wave of mammal extinctions in the middle (pre-Pleistocene) Quaternary. But there was recovery. Many factors figure in, including climates and continental drift. Sometimes, the change due to organic evolution is overwhelmed by the change due to climatic cooling or drying out. The change due to organic evolution may be accelerated or decelerated by continental drift; continents fused together may provide a bigger area that supports more species, or they may provide more competition that eliminates species that previously evolved on separated continents. If the tectonic plates drift together and form a supercontinent, the supercontinent may saturate (some think), and if afterward the continents drift apart, this may add to the provinciality of the world and facilitate by isolation the evolution of diversity. On the whole organic evolution has “the result that the present diversity of the world’s plants and animals is (or was just before our species appeared) probably greater than it has ever been before” (Pielou 1975:150).
Figure 2.10 Changes in species diversity in Silurian-Tertiary times
Figure 2.11 Diversity of fossil vertebrates (Padian and Clemens 1985)
John Bonner, in a detailed study of the evolution of complexity, summarizes his findings:
There has… been an extension of the upper limit of complexity during the course of evolution…. There has also been an increase in the complexity of animal and plant communities, that is, there has been an increase in the number of species over geological time, and this has meant an increase in species diversity in any one community…. One can conclude that evolution usually progresses by increases in complexity…. As evolution proceeded on the surface of the earth, there has been a progressive increase in size and complexity. (Bonner 1988:220, 228, 245)
Life’s big bang explodes in an extravaganza, in both diversity and complexity.
Expanding Neuro-sentience: Felt Experience
With the emergence of neurons, arranged in neural networks, this exploding complexity reached sentience. This continued the life explosion, deepening and transcending the cybernetic dimensions. A neuron is functionally “for” information detection and transfer. Neurons make possible acquired learning, acquiring information and storing it for future use in the lifetime of the individual. Behavior is more labile, less stereotyped. With neuronal nets of increasing complexity, a new threshold is crossed; there appears felt experience. As with everything else in evolutionary development, this takes place gradually, but that ought not to obscure the fact that there is momentous emergent novelty. With increasing neuronal complexity, there appears inwardness. With still more, there appear what philosophers call qualia, consciously entertained experiential mental states such as sensations, feelings, perceptions, desires. Increasingly, there is “somebody there”; objects evolve into subjects with psyche. There is “something it is like” to be that subject-organism. There appears phenomenology of experience, as when a person (or a rat?) smells strong cheese.
Analyzed at the molecular level, neurons involve the flow of various ions, electric currents, often across membranes, as with synaptic connections. These processes can as well be considered complex chemistries. Living organisms, from the start of life, have been doing non-nervous metabolisms interacting with ions and their bonding chemistries, including some signaling and stimulus-response perceiving. Plants detect and act upon signals within their environments. A protozoan may move up a gradient toward light or food. Sometimes biologists and philosophers have wondered whether low-grade felt awareness might accompany such perceiving even in non-neuronal organisms (Bray 2009; Jennings 1906:336–337), but most hold that felt experience, psyche, requires neurons.
Just when and how what might be a precursor to neurons appeared is not known, although there is some evidence this was about 700 million years ago. The diversity of existing nervous systems is enormous. Some scientists have wondered if nerves evolved independently more than once, although recent opinion, based on genetic and molecular analysis, indicates a single (monophyletic) origin (Hirth and Reichart 2007). The most primitive organisms to possess a nervous system are cnidarians, a phylum of mostly marine animals. In their diffuse nervous systems (as found in jellyfish, sea anemones, corals
), nerve cells are distributed throughout the organism, often organized into nerve nets with synapselike connections, perhaps with ganglia, local concentrations of neurons. Sensory neurons connect with effector neurons without central integration. Presumably there is present some diffuse experience of feeling; it is difficult to know.
Central nervous systems evolved later. It is not known when they first appeared in animal evolution nor what their earliest function was. The presumed earliest ancestors are identified as “urbilateria,” of which there are fossil traces (Arendt et al. 2008). Flatworms exhibit bilateral symmetry, breaking previously radial symmetry. This more is different. The nervous system evolved to consist of longitudinal nerve cords, with peripheral nerves connecting to sensory cells, and at one end a “brain,” as for instance in the two joined cephalic ganglia in Planaria. There does appear to be present felt experience, though such mental states are simple, without capacity for introspection (Tye 1997). There are endorphins (natural opiates) in earthworms, which indicates both that they suffer and that they are naturally provided with pain buffers (Alumets et al. 1979).
Alain Ghysen finds that central nervous systems probably originated in a single species with a sophisticated enough nervous system to be both conserved in basic features and dramatically elaborated in the myriads of brained species that have characterized evolutionary history. “The appearance of very different life forms, lifestyles and habitats requires the previous attainment of a neural circuitry that is sufficiently robust to cope with large changes without losing its overall coherence” (Ghysen 2003:555). So nerve cells appear, and radically elaborate and escalate capacities across evolutionary history. There is a sense, however, in which calling this elaboration and escalation obscures the radical momentous innovation of subjectivity appearing where before was only objectivity.
It may seem that the evolutionary account is delivering subjectivity and felt experience bit by bit, incrementally rather than swiftly, but it is also true that felt experience appears where absolutely none was before. Incremental qualities joined and rejoined are also reformed and transformed into novel qualities. One gets, at length, pleasure and pain by organizing millions of unfeeling atoms. Slowing things down and putting together molecular parts does not really alleviate the lack of theory explaining how inwardness comes out of outwardness. It only spreads the inexplicable element thin, rather than asking us to swallow it in one lump.
We do not know how, much less why, there emerges out of the neural electronics and chemistry this capacity for conscious experience and caring. The molecular accounts of currents and chemistries in neurons describe the technical conditions necessary for the production of subjective experience, with no account of the necessary or intelligible derivation of what emerges. “Nobody has the slightest idea how anything material could be conscious. Nobody even knows what it would be like to have the slightest idea about how anything material could be conscious” (Fodor 1992:5).
The physical world that resulted from the first big bang could not feel pain or pleasure. But with advancing formational and informational levels, life crossed another singularity: increasing capacity for felt experience. A planet moves through an environment, but only an organism can need its world, a feature simultaneously of its prolife program and of the requirement that it overtake materials and energy. But if the environment can be a good to it, that brings also the possibility of deprivation as a harm. To be alive is to have problems. Things can go wrong just because they can also go right. In an open, developmental, ecological system, no other way is possible. All this first takes place at insentient levels, where there is bodily duress, as when a plant needs water.
Irritability is universally present in life; suffering in some sense seems copresent with neural structures. Sentience brings the capacity to move about deliberately in the world, and also to get hurt by it. We might have sense organs—sight or hearing—without any capacity to be pained by them. But sentience was not invented to permit mere observation of the world. It rather evolved to awaken some concern for it. Sentience coevolved with a capacity to separate the helps from the hurts in the world. A neural animal can love something in its world and is free to seek this, a capacity greatly advanced over anything known in immobile, insentient plants. It has the power to move through and experientially to evaluate the environment. The appearance of sentience is the appearance of caring, when the organism is united with or torn from its loves. The earthen story is not merely of goings-on, but of “going concerns.” The step up that brings more drama brings suffering.
Further, pain is an energizing force. Suffering not only goes back-to-back with caring sentience but also drives life toward pleasurable fulfillment. The good presupposes concomitant evil, but the evil is enlisted in the service of the good. Individually, the organism seeks to be rid of pain, and yet pain’s threat is self-organizing. It forces alarm, action, rest, withdrawal. It immobilizes for healing. The organism is quickened to its needs. The body can better defend itself by evolving a neural alarm system. The experiences of need, want, calamity, and fulfillment have driven the natural and cultural evolution of abilities to know, and in due course abilities to think. Where pain fits into evolutionary theory, it must have, on statistical average, high survival value, with this selected for, and with a selecting against counterproductive pain. In this sense, pain is a prolife force.
The evolutionary explosion is driven by conflict and resolution. All advances come in contexts of problem solving, with a central problem in sentient life the prospect of hurt. We do not really have available any coherent alternative models by which, in a painless world, anything like the explosion of life on Earth might have taken place. The system summarizes the lives of individuals in their conflict and resolution, using this to innovate by spinning out biodiversity and biocomplexity. Adapted fit seems at first a good thing, but then the shadow side is how each organism is doomed to eat or be eaten, to stake out what living it can competing with others. Perhaps there is more efficiency than waste, more fecundity than indifference, but each organism is ringed about with competitors and limits, forced to do or die. Each is as much set against the world as supported within it.
Seen more systemically, the context of creativity logically and empirically requires this context of conflict and resolution. An environment entirely hostile would slay life; life could never have appeared within it. An environment entirely irenic would stagnate life; advanced life, including human life, could never have appeared there either. Oppositional nature is the first half of the truth; the second is that none of life’s explosive advance is possible without this dialectical stress. Muscles, teeth, eyes, ears, noses, fins, legs, wings, scales, hair, hands, neurons, brains—all these and almost everything else comes out of the need to make a way through a world that mixes environmental resistance with environmental conductance.
The system, from the perspective of the individual, is built on competition and premature death. Seen systemically, that is the generating and testing of selves by conflict and resolution, such values required to be both prolific and adapted fits. Such conflict in resolution does result in better-adapted fit, where the organism occupies a niche providing life support in an ecology of interdependent, mutually supporting species. Partnerships and symbioses too are vital in the evolutionary history of life.
The evolutionary story could be titled, “The Evolution of Caring,” positively the capacity to enjoy pleasures. Or, perversely if one prefers, “The Evolution of Suffering.” Each seeming advance—from plants to animals, from instinct to learning, from sentience to self-awareness, from nature to culture—steps up the pain. It is difficult to extrapolate to animal levels and make judgments about the extent of their suffering. A safe generalization is that pain becomes less intense as we go down the phylogenetic spectrum, and is often not as acute in the non-human as in the human world (Eisemann et al. 1984).
No doubt there was an evolutionary genesis of neurally based mind, capable of conscious plea
sures and pains. But we have no logic by which out of physical premises, one derives biological conclusions, and taking these as premises in turn, one then derives psychological conclusions. Are neurons and the consciousness they produce somehow precontained in the first big bang? Are they even precontained in the second? Nevertheless, there is no doubt that animal life gets psyche, and that higher forms of animal life get psyched up. Matter starts to get animated, spirited. Maybe we are here getting hints of headings toward the third big bang?
Escalating Co-option: Serendipity
A major feature of genetic natural history is co-option generating novel, nonlinear possibilities. An existing gene and its product are recruited to a new function, with serendipity. For example, lens crystallins used in eyes first evolved in an altogether different role, as heat-stress proteins. They happened to be transparent. Surprisingly, they get used to make eye lenses, and more than once (Wistow 1993). Darwin had already noted that this could happen: “The swimbladder in fishes… shows us clearly the highly important fact that an organ originally constructed for one purpose, namely flotation, may be converted into one for a wholly different purpose, namely, respiration” (Darwin 1968:220–221). So the movement of life from sea to land was by co-option.
There are remarkable forks off preexisting pathways. Often, though not always, there is gene duplication and one copy serves the former function while the new copy can be modified in exploratory directions. Previously disconnected parts working along unrelated pathways are co-opted off and put together to start serving a novel function, perhaps only slightly well at first. Radically different selection pressures begin to work in new directions that are completely unanticipated when they occur. Once launched, the novel functions may improve steadily and completely transform the course of natural and human history.