|
The Problem of the Population of One
Life as a Planetary Process. One of the most important empirical facts recognized in recent decades is that the Earth at the planetary level evolves as a single global entity (e.g., Cloud, 1988; Margulis & Lovelock, 1974; Schwartzman, et al., 1994; Swenson &Turvey, 1991; Vernadsky, 1986/1929). The present oxygen rich atmosphere, put in place and maintained by life over geological time, is perhaps the most obvious prima facie evidence for the
existence and persistence of the planetary entity. With the shift
of the Earth's redox state from reducing to oxidative some two
billion years ago evolution undeniably became a coherent planetary
process. Figure 1 shows the redox state shift and theincrease
in atmospheric oxygen over evolutionary time that followed until
it reached its present atmospheric level. Figure 1 also shows
the progressive emergence of more highly ordered forms as a function
of increasing levels of atmospheric oxygen. Studies with shapes
of things and their metabolic and respiration capacities (e.g.,
Runnegar, 1982) suggest that order, as noted above, seems to
come into being as soon as minimal thresholds, in this case oxygen,
are reached. Both the progressive increase in atmospheric oxygen
and the production
|
of increasingly more highly
ordered states constitute an increasing departure of the global
system from equilibrium, again, as Fisher noted, running opposite
to that generally assumed to be the predicted direction for physical
evolution according to the second law.
The Problem for Darwinian Theory. The fact that the evolution
and persistence of all the higher-ordered living states that
have been the typical objects of evolutionary study (e.g., sexually
reproducing animals) are dependent on a rich and steady supply
of atmospheric oxygen makes them dependent upon the prior evolution
and persistence of life at the planetary level for their existence.
More precisely, they are internal productions of the larger planetary
process or, in Vernadsky's (1929, p. 489) words they are regular
"functions" of the biosphere. This suggests that the
study of evolution at the planetary level is the study of the
most fundamental entity of terrestrial evolution without an understanding
of which all the other living things that are effectively component
productions will never be understood. Yet this poses a major
problem for Darwinian theory because the planetary system as
a whole cannot, by definition, be considered a unit of Darwinian
evolution (Maynard-Smith, |
