Whether for spiritual, scientific, or ontological purpose, the matter of defining life is an ancient and serious quest. The Gaian theory of earth science – so named for Gaia, the Greek goddess of the Earth – proposes that the physical Earth upon which we live is just as alive as we animals and the plants are. The scientist James Lovelock proposed in the mid 1960s that the Earth, far from being just a mobile mass in space hospitable to animal and plant life, is a self-regulating ecosystem that calls on the fields of geology and physiology to explain its potential status as a live organism.
Essentially, Lovelock’s hypothesis is that the physical planet Earth is active in response to the organisms living in and on it. These organisms evolve in tandem with the Earth in a process that yields homeostasis for the planet. The Earth regulates its own climate and chemical state in a way that promotes and sustains biodiversity while subscribing to the Darwinian truth of natural selection. Should we define life, we could say that something that has life is in a bounded forma and has something close to a survivalist instinct, whereby it distinguishes between predator and prey, and can identify potential mates. As Lovelock colorfully summarizes this principle, “We all know intuitively what life is. It is edible, lovable, or lethal.”
The science of Gaia has gained in popularity since its conception, but it is not exactly mainstream. Biologists and botanists alike have criticized Lovelock’s theory as clever and teleological, but not entirely scientifically plausible. While the idea that the Earth is physically alive may be quite jarring to think about, Gaia explains, in a way that is more holistically satisfying than any hypotheses to date, how our Earth functions and continues to exist. Homeostasis in the Earth’s climate and chemical composition, as predicted and proven by Gaian theory, allows us to view the Earth and the living organisms on it as part of a sunlight-dependent system that is self-regulatory in terms of temperature and chemical composition of the crust. This very crust, along with the Earth’s oceans and air are geochemically composed of historical organisms, such as ancient sea creatures with limestone shells. The limestone we have no on Earth is a remnant of these creatures, and it affects the environments and habitats of the organisms that are alive now. The four basic principles of Gaia take for granted that living organisms will use their environments to benefit their own survival and reproduction rates, in agreement with Darwinian theory of evolution. These organisms affect their own physical and chemical environment in both beneficial and detrimental ways. For example, in the interest of agriculture, humans have been clearing forests for at least hundreds of years, if not thousands. While forest-clearing technology may be viewed as a useful tool contributing to human sustenance and self-sufficiency, it has also contributed to a greater amount of carbon dioxide in the atmosphere because of the absence of photosynthesizing trees in spaces where trees once flourished. In this way, humans have both positively and negatively impacted their environment. However, Gaia is not a passive, static being. The Earth controls environmental hospitality for living organisms by adapting to the impact these organisms make on the Earth.
NASA voyages into outerspace encouraged Lovelock to examine why life is successful on Earth but not on other planets, specifically Mars and Venus, which share essentially the same elements as Earth and in relatively similar proportions, but do not support life. From the beginning of these space voyages, Lovelock took a different tack than his colleagues, assuming that the instruments that measure life on Earth are inadequate for measuring or even finding life on other planets. We must go into foreign territory expecting nothing familiar, Lovelock presumed, somewhat obviously yet still somehow in opposition to his peers at NASA. He concluded that the elements that make up Earth – air, ocean, soil, etc. – are as much a part of life as the organisms that we classify as living. These elements are essential to the survival of organisms on Earth, and thus can be considered parts of a living system. We humans need air to breathe and also to regulate the inhospitable temperatures of space. Air is not so much a part of our life-sustaining environment as it is a part of life itself.
What we can take from the Gaia hypothesis is a holistic model of the Earth and its ecosystems that may also be broken down to the human level for a different and interesting analysis. Human bodies are on average 70% water, roughly the same proportion as water on earth. The Earth has an interest in maintaining a hospitable salt proportion in its waters. The process of seawater evaporation in the water cycle allows for salt to precipitate out of the seawater. Our bodies have the same interest in removing perceived impurities from themselves, or elements that, in excess, are inhospitable to life; the kidneys are effective in removing waste from our blood via its own purifying system.
Gaia is a beautifully comprehensive theory of life. In the ageless struggle to define life, we can include in our definition those systems and elements that allow us and other living things to be alive. The water that I drink to hydrate my body’s cells is more than just an agent to keep me alive; rather, it is a part of my body’s life. The Earth that affords me a hospitable habitat is part of my life cycle, and part of life itself.
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