FunNature & AnimalIs the Earth a living organism?

Is the Earth a living organism?

In the year 1969, the meteorologist James Lovelock developed one of his most revolutionary ideas. In it, he argued that the earth as a whole is a self-regulating system that tends towards homeostasis . He called it the Gaia hypothesis , after the Greek deity.

According to this hypothesis, the most superficial part of the earth, together with the atmosphere and the hydrosphere and the biosphere itself, form a group capable of self-regulation , through feedback between its different parts, in a constant search for physical and chemical balance, which results optimal for life.

daisy world

To make the hypothesis understandable, James Lovelok and Andrew Watson designed the daisy world simulation. A hypothetical world, deserted and frozen, that orbits around a sun that provides it with more and more heat. In this world there are only two daisies, some black, which live better when it’s cold, and others white, which prefer warm environments.

By planting daisies on the deserted and frozen planet, initially only black ones grow . But these daisies collect heat from the sun due to their pigmentation, warming your world, and allowing white daisies to grow . However, when they begin to abound, the albedo causes them to reflect more sunlight, which cools the planet.

Throughout the simulation, a bare planet would be getting warmer and warmer due to the action of the sun; the paradox is that the temperature remains stable on the planet of daisies, in equilibrium , during most of the simulation, thanks to the interaction between the daisies and the temperature.

Throughout the history of life, episodes have been observed in which life shapes the environment to, apparently, make it more appropriate for life itself. For example, for billions of years, countless numbers of cyanobacteria have been altering the composition of the Earth’s atmosphere , from a reducing form, based on carbon dioxide, to the atmosphere we know today, oxidizing and with 21% carbon dioxide. oxygen approx.

The problem of purpose

However, there is one aspect that conflicts with this idea, which we can deduce from the example of cyanobacteria. They did not expel oxygen to make the earth a more suitable place for life. That was not their purpose, if they had any. At that time respiration did not yet exist, heterotrophic organisms were fermenters and oxygen was extraordinarily toxic. The cyanobacteria were, in fact, making the world a more uninhabitable place for the life forms that coexisted with them.

But life makes its way . And it was biological evolution itself that developed ways to defend against the massive oxygen pollution that threatened to wipe out all life. The breathing process arose, and the organisms capable of tolerating that oxygen and taking advantage of it to obtain their energy, turned out to be more apt than those that did not have that property. The world was populated with life capable of breathing.

The result looks the same, but the nuance is important. Not that cyanobacteria promoted a more habitable world. There was no such purpose, they only discarded what was not useful to them, what was toxic, and it was biological evolution that, by mere chance, and without any purpose , gave rise to life forms capable of surviving.

This creates a new dilemma. At what moments in the history of life has the Gaia hypothesis worked? Of course, the interaction between living beings and their environment is an undeniable fact. However, whether this interaction is constructive and in favor of optimal conditions is highly debatable. There are situations in which living beings have been responsible for interactions contrary to the interest of life in general, and in which life has managed to survive thanks, not to a balance achieved by following a purpose, but to biological evolution itself.

The dilemma with evolution

Some evolutionary biologists have strongly opposed the Gaia hypothesis . As biological evolution is understood, there is nothing in the genome of living beings that can provide the feedback mechanisms proposed by Lovelock. Furthermore, the evolutionary process is not teleological, that is, it does not act with foresight, planning, or purpose.

Even the operation of the daisy world simulation can be a trap: it works because it is designed to work, and it can’t not work . The simulation is based on premises such that its operation is unavoidable, however, if the premises are changed —for example, that black daisies prefer heat and white daisies prefer cold—, the results are very different and break the predictions of the hypothesis.

Different degrees of Gaia hypothesis strength have been differentiated. At one extreme would be the weak Gaia , according to which feedbacks have no purpose and are the result of ecological dynamics and interactions between organisms and their environment, and even at an evolutionary level.

At the opposite extreme would be the strong Gaia , in which the biota obeys a principle with a determined purpose, and works together to optimize the land.

The extreme of the weak Gaia, that level of ecological interaction, with a feedback influence between the environment and living beings, and with a system of co-evolution, have already been accepted and explained by ecosystem dynamics, natural selection and adaptation, and do not represent any scientific novelty. . At this low-strength level it is often stated that the Gaia hypothesis works, but it is unnecessary .

The strongest forms of the Gaia hypothesis, however, have not yet found sufficient scientific footing, and it is not something that accepts scientific consensus; to the point that many scientists consider Gaia to be a dead end .

If supporters and detractors of the Gaia hypothesis agree on something, however, it is in its contribution to the change of point of view. A launch pad towards knowledge , which although based on ideas with little foundation or contrary to certain knowledge, opens the door to very interesting questions that science can answer .


Dawkins, R. 1983. The extended phenotype: the long reach of the gene. Oxford University Press.
Free, A. et al. 2007. Do evolution and ecology need the Gaia hypothesis? Trends inEcology & Evolution, 22(11), 611-619. DOI: 10.1016/j.tree.2007.07.007
Tyrrell, T. 2013. On Gaia: a critical investigation of the relationship between lifeand Earth. Princeton University Press.

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