Indeed, the image of Gaia as a sentient being was the main implicit argument for the rejection of the Gaia hypothesis after its publication. Scientists expressed it by claiming that the hypothesis was unscientific because it was teleological—that is, implying the idea of natural processes being shaped by a purpose. “Neither Lynn Margulis nor I have ever proposed that planetary self-regulation is purposeful,” Lovelock protests. “Yet we have met persistent, almost dogmatic, criticism that our hypothesis is teleological.” 67
This criticism harks back to the old debate between mechanists and vitalists. While mechanists hold that all biological phenomena will eventually be explained in terms of the laws of physics and chemistry, vitalists postulate the existence of a nonphysical entity, a causal agent directing the life processes that defy mechanistic explanations. 68 Teleology—from the Greek telos (“purpose”)—asserts that the causal agent postulated by vitalism is purposeful, that there is purpose and design in nature. By strenuously opposing vitalist and teleological arguments, the mechanists still struggle with the Newtonian metaphor of God as a clockmaker. The currently emerging theory of living systems has finally overcome the debate between mechanism and teleology. As we shall see, it views living nature as mindful and intelligent without the need to assume any overall design or purpose. 69
The representatives of mechanistic biology attacked the Gaia hypothesis as teleological, because they could not imagine how life on Earth could create and regulate the conditions for its own existence without being conscious and purposeful. “Are there committee meetings of species to negotiate next year’s temperature?” those critics asked with malicious humor. 70
Lovelock responded with an ingenious mathematical model, called “Daisyworld.” It represents a vastly simplified Gaian system, in which it is absolutely clear that the temperature regulation is an emergent property of the system that arises automatically, without any purposeful action, as a consequence of feedback loops between the planet’s organisms and their environment. 71
Daisyworld is a computer model of a planet, warmed by a sun with steadily increasing heat radiation and with only two species
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growing on it—black daisies and white daisies. Seeds of these daisies are scattered throughout the planet, which is moist and fertile everywhere, but daisies will grow only within a certain temperature range.
Lovelock programmed his computer with the mathematical equations corresponding to all these conditions, chose a planetary temperature at the freezing point for the starting condition, and then let the model run on the computer. “Will the evolution of the Daisy world ecosystem lead to the self-regulation of climate?” was the crucial question he asked himself.
The results were spectacular. As the model planet warms up, at some point the equator becomes warm enough for plant life. The black daisies appear first because they absorb heat better than the white daisies and are therefore more fit for survival and reproduction. Thus in its first phase of evolution Daisyworld shows a ring of black daisies scattered around the equator (figure 5-5).
Figure 5-5
The four evolutionary phases of Daisyworld.
As the planet warms up further, the equator becomes too hot for the black daisies to survive and they begin to colonize the subtropical zones. At the same time, white daisies appear around the equator. Because they are white, they reflect heat and cool themselves, which allows them to survive better in hot zones than the black daisies. In the second phase, then, there is a ring of white daisies around the equator and the subtropical and temperate zones are filled with black daisies, while it is still too cold around the poles for any daisies to grow.
Then the sun gets hotter still and plant life becomes extinct at the equator, where it is now too hot even for the white daisies. In the meantime white daisies have replaced the black daisies in the temperate zones, and black daisies are beginning to appear around the poles. Thus the third phase shows the equator bare, the temperate zones populated with white daisies, and the zones around the poles filled with black daisies with just the pole caps themselves without any plant life. In the last phase, finally, vast regions around the equator and the subtropical zones are too hot for any daisies to survive, while there are white daisies in the temperate zones and black daisies at the poles. After that it becomes too hot
on the model planet for any daisies to grow and all life becomes extinct.
These are the basic dynamics of the Daisyworld system. The crucial property of the model that brings about self-regulation is that the black daisies, by absorbing heat, warm not only themselves but also the planet. Similarly, while the white daisies reflect heat and cool themselves, they also cool the planet. Thus heat is absorbed and reflected throughout the evolution of Daisyworld, depending on which species of daisies are present.
When Lovelock plotted the changes of temperature on the planet throughout its evolution, he got the striking result that the planetary temperature is kept constant throughout the four phases (figure 5-6). When the sun is relatively cold, Daisyworld increases its own temperature through heat absorption by the black daisies; as the sun gets hotter, the temperature is lowered gradually because of the progressive predominance of heat-reflecting white daisies. Thus Daisyworld, without any foresight or planning, “regulates its own temperature over a vast time range by the dance of the daisies.” 72
Feedback loops that link environmental influences to the growth of daisies, which in turn affect the environment, are an essential feature of the Daisyworld model. When this cycle is broken so that there is no influence of the daisies on the environment, the daisy populations fluctuate wildly and the whole system goes chaotic. But as soon as the loops are closed by linking the daisies
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back to the environment, the model stabilizes and self-regulation occurs.
Since then Lovelock has designed much more sophisticated versions of Daisyworld. Instead of just two, there are many species of daisies with varying pigments in the new models; there are models in which the daisies evolve and change color; models in which rabbits eat the daisies and foxes eat the rabbits; and so on. 73 The net result of these highly complex models is that the small temperature fluctuations that were present in the original Daisyworld model have flattened out, and self-regulation becomes more and more stable as the model’s complexity increases. In addition, Lovelock put catastrophes into his models, which wipe out 30 percent of the daisies at regular intervals. He found that Daisyworld’s selfregulation is remarkably resilient under these severe disturbances.
All these models generated lively discussions among biologists, geophysicists, and geochemists, and since they were first published the Gaia hypothesis has gained much more respect in the scientific community. In fact, there are now several research teams in various parts of the world who work on detailed formulations of the Gaia theory. 74
MODELS OF SELF-ORGANIZATION
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In the late 1970s, almost twenty years after the key criteria of selforganization were discovered in various contexts, detailed mathematical theories and models of self-organizing systems had been formulated, and a set of common characteristics became apparel continual flow of energy and matter through the system, the stable state far from equilibrium, the emergence of new patterns of order, the central role of feedback loops, and the mathematical description in terms of nonlinear equations.
At that time the Austrian physicist Erich fantsch, then at the University of California at Berkeley, presented an early synthesis of the new models of self-organization in a book titled The Self- Organizing Universe, which was based mainly on Pngogine’s theory of dissipative structures. 75 Although Jantsch’s book is now largely outdated, because it was written before the new mathematics of complexity became widely known and because it did not include the full concept of autopoiesis as the organization of living systems, it was of tremendous value at the time. It was the first book that made Prigogine’s work available to a broad audience, and it attempted to integrate a large number of then very new concepts and ideas into a coherent paradigm of self-organization. My own synthesis of these concepts in the present book is, in a sense, a reformulation of Erich Jantsch’s earlier work.
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