The 1960s and 1970s were a time of explosive creativity in music and the arts. That’s what we remember most about that period. We still listen to ‘golden oldies’ of Santana, the Beatles, and others. But it was also a creative time in other fields, such as engineering. With the growing importance of computers, the systems concept became more widely known. Soon flowcharts and system-speak like “input”, “output”, and “feedback” were showing up almost everywhere.

Whether organic, mechanical, or electronic, a system is composed of interrelated and interacting parts. In biology, systems analysis can be applied to a single cell or to an entire organism. Ecologists recognized that the addition or subtraction of a single species could affect all of the life in a region, and in that sense, the ecology of a place is also a system.

James Lovelock took the system idea even further and applied it to the whole world. Originally from England, with a Ph.D. in medicine, Lovelock worked for NASA during the 1960s studying the possibility of life on Mars. He was struck by the differences between the Martian atmosphere and that of Earth. During this period he began writing articles about what he called “the earth feedback hypothesis”. Back in England, a neighbor, novelist William Golding [best known for his book The Lord of the Flies], suggested he name it for the Greek mother goddess. The name, Gaia Hypothesis, gave Lovelock’s idea more appeal to environmentalists. He published the first full length book on the topic in 1979.

So what is the Gaia Hypothesis? It proposes that both physical and organic processes work together to produce an environment favorable to life on Earth. Lovelock noted that Earth’s atmosphere maintains a relatively constant composition; the salinity of the ocean should be increasing but remains stable; and the surface temperature stays constant within certain boundaries suitable for life. The reason for this homeostasis is that life is constantly reacting to feedback and adjusting itself and the environment to suit its own needs. The process is unconscious but effective, and so Gaia functions like a super organism.

Our present atmosphere is 78% nitrogen, 21% oxygen, and the remainder is carbon dioxide, water vapor and other gases. The early atmosphere of Earth held little free oxygen. Like our sister planets, Mars and Venus, Earth’s atmosphere was probably almost entirely carbon dioxide for roughly the first two billion years. We know this because in today’s atmosphere iron rusts, but in those early times only partly oxidized iron was deposited on ocean floors. Other minerals also formed then that cannot form today.

By 3.5 billion years ago cyanobacteria were common in shallow parts of the oceans. Through photosynthesis they stripped the carbon from carbon dioxide and released oxygen. As a result of their actions, by 750 million years ago the oxygen levels on Earth were about 10% of what they are now, and they continued rising to the present level. More oxygen could produce great wildfires, and there is evidence that this happened during the Carboniferous Period, when oxygen may have been 35% of the air. Some oxygen went into the ozone layer about 2.4 billion years ago; ozone is a different molecular form of oxygen. Life on land would be impossible without the ozone layer because it blocks ultraviolet radiation from the sun.

In addition, the volume of carbon dioxide was reduced by organic actions that created limestone, [calcium carbonate]. The remainder of carbon dioxide in the atmosphere maintains surface temperature. Too much, the world warms; too little, it freezes.

I never paid much attention to the Gaia HypothesisypoHH. It struck me as more of a metaphor than a scientific theory. And some of the proponents of the idea write about it as though Gaia were a conscious entity. This seems like mysticism or neo-paganism. There are plenty of other critics, including Richard Dawkins and the late Stephen Jay Gould, some of whom are comfortable with the systems analysis but not the personification of the system, or the idea that our planet as a whole is a living being.

In 2009, Peter Ward, author of many books on paleontology for the general reader published The Medea Hypothesis, opposing Gaia theory. Who was Medea? There are many stories about her; ancient authors were seldom consistent in telling the myths. For our purposes, she was a bad mother. The best known version is that she was a princess of Colchis, who eloped with Jason, the Argonaut. When Jason abandoned her for a princess of Corinth, Medea got revenge by killing their two children. Ward’s point is that Mother Earth sometimes kills her children. We are especially cognizant of this right now with the earthquake in Haiti on our minds. But that devastation was caused by tectonic forces; Ward contends that life can cause its own destruction.

All species compete for resources, and unthinking reproduction can exceed the carrying capacity of a habitat. The main villains in Ward’s mind are the original form of life, the prokaryotes – bacteria and archaea. Although this group was responsible for giving Gaia her oxygen, some of them cannot live with the gas. Instead, they process sulfur for metabolism and give off hydrogen sulfide, a gas lethal to oxygen breathers. Ward believes that prokaryotes are implicated in several of the fifteen or more big die-offs in geologic history. The greatest mass extinction occurred at the end of the Permian, 251 million years ago. Here’s Ward’s scenario: The eruption of the Siberian Traps [massive flood basalts] filled the atmosphere with carbon dioxide, which warmed the Earth. That slowed the oceanic currents, causing the waters to become depleted of oxygen. These conditions allowed sulfur bacteria to bloom and fill the atmosphere with hydrogen sulfide, which killed both plants and animals worldwide. Where was Gaia then?

Ward does give the Gaia Hypothesis some credit. He says that an offshoot of the Gaia idea was the creation of a new field of study called Earth System Science, which has greatly enriched our understanding of the world we live on.

The Gaia hypothesis is comforting – life will react to feedback and adjust the world system to maintain a comfortable environment for life – but even Lovelock is not sanguine about our future. As we continue disrupting the natural processes, by burning fossil fuels and deforestation, we are destroying the intricate balance of Gaia. He has called humanity “an infection” and predicted that global warming will cause the Sahara Desert to cross the Mediterranean Sea, degrading living conditions as far north as Paris. Yes, eventually Gaia would adjust living conditions, but in a geologic time frame much to long for civilization as we know it to survive.