Figure 1. Buildup of atmospheric O2 in geological time (PAL is present atmospheric level). From Swenson, (1989a), p. 71. Copyright 1989 IEEE. Reprinted by permission

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,