On the issue of directionality and determinism in biologic evolution, I
generally agree with Jim Farmelant. Teleology implies goal-seeking.
Massive stars evolve deterministically to supernovas, but I wouldn't call
this example of self-organization teleological. With respect to
biotic/biospheric evolution, I offer the following excerpt from my book
(from chapter 1, Life, Temperature, and the Earth, 1999, Columbia
University Press):
"A theory of biospheric evolution
... Both the beginning and end of life on this planet are determined by
purely non-biological conditions, the beginning by the hydrothermal
activity on the ocean floor, where the origin of life took place, the end
by the rising radiant energy flux from the sun. But between these times,
predetermined by the initial conditions of our solar system, the
biosphere evolves in its overall patterns deterministically, going from a
hothouse with surface temperatures near 100 deg
C to an icehouse, with intermittent glacial periods, then in the future
back into a hothouse regime before its destruction. A progressive
increase in the diversity of habitats for life and a concomitant biotic
evolutionary explosion has occurred in the last 4 billion years, only to
be reversed in the future with a return to the hothouse. ...Surface
temperature is a critical constraint on the tempo of major events in
biotic evolution, while itself being determined by a progressively
increasing role of biota in climatic change over geologic time, within
the context of abiotic evolution (solar and terrestrial). The
temperature constraint has occurred because each major innovation in
biological evolution, such as oxygenic photosynthesis (emergence of
cyanobacteria), has an inherent biochemical and biophysical upper
temperature limit for its metabolism. Thus, with the long term cooling
of the Earth's surface, new metabolisms and cell types became possible as
their upper temperature limit was reached. Cooling occurred because of
the combined effects of abiotic variations, such as volcanic outgassing
rates and rising solar luminosity, and the progressively powerful effect
of land biota on the sequestering of carbon from the atmosphere by the
chemical weathering process in soils. ...
The biosphere has evolved deterministically as a self-organized
system, given the initial conditions of the Sun-Earth system. The origin
of life and the overall patterns of biotic evolution were highly probable
outcomes of this deterministic process. These overall patterns include
the emegence of oxygenic photosynthesis, and the history of
endosymbiogenesis that resulted in the emergence of Eukarya ("complex"
life) and its Kingdoms. Evolution of procaryotes and complex life on
terrestrial planets around Sun-like stars are expected to have similar
geochemical and climatic consequences. The width of the habitable zone
for Earth-like planets around Sun-like stars for complex life may be
substantially smaller than that for the appearance of biota, constrained
by the presence of liquid water. Surface temperature history on
terrestrial planets may be critical to the time needed to evolve complex
life and intelligence. Biotically-mediated cooling increases the width
of the habitable zone for the possible occurrence and evolutionary time
frame of complex life. For Earth-like planets within the habitable zone
of stars less massive than the Sun, the earlier emergence of complex
life is expected, all other factors being the same."
Finally, on the question of contingency, if I might make an analogy to
the possibility of nuclear war aborting human historical development, a
big enough impact, though improbable, could have sterilized the Earth's
surface at any time between now and the origin of life, thereby cutting
off further biotic/biospheric evolution. Of course the difference between
nuclear war and impact is that our own lifeform can influence the chances
of the former, but not the latter except perhaps in the future (e.g., by
using nuclear weapons to divert the course of an Apollo object heading to
Earth, an option not available to any other lifeform in the history of
the Earth). I would not of course argue that every detail of
biotic/biospheric evolution has been deterministic (e.g. at species
level, or this message!). Readers might like to look at the chapter of my
book "Self-Organization of the Biosphere', especially my attempt to
summarize some theses in a dialectical theory with explicit reference to
Marxist philosophy of science (Like Levins and Lewontin, I too dedicate
my book to Fred Engels, among others including Vernadsky, Lovelock and
Margulis). Well that's enough for my first intervention on this list.
David Schwartzman
Department of Biology
Howard University
Washington, DC 20059
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