Cosmologic philosophy: gaia is back (Introduction)

by David Turell , Sunday, January 22, 2017, 15:41 (2862 days ago) @ David Turell

An essay supporting the concept of a living Earth:

http://nautil.us//issue/44/luck/why-most-planets-will-either-be-lush-or-dead?utm_source...

"Studying Earth’s global biosphere together, Margulis and Lovelock realized that it has some of the properties of a life form. It seems to display “homeostasis,” or self‐regulation. Many of Earth’s life‐sustaining qualities exhibit remarkable stability. The temperature range of the climate; the oxygen content of the atmosphere; the pH, chemistry, and salinity of the ocean—all these are biologically mediated. All have, for hundreds of millions of years, stayed within a range where life can thrive. Lovelock and Margulis surmised that the totality of life is interacting with its environments in ways that regulate these global qualities. They recognized that Earth is, in a sense, a living organism. Lovelock named this creature Gaia.

"Margulis and Lovelock showed that the Darwinian picture of biological evolution is incomplete. Darwin identified the mechanism by which life adapts due to changes in the environment, and thus allowed us to see that all life on Earth is a continuum, a proliferation, a genetic diaspora from a common root. In the Darwinian view, Earth was essentially a stage with a series of changing backdrops to which life had to adjust. Yet, what or who was changing the sets? Margulis and Lovelock proposed that the drama of life does not unfold on the stage of a dead Earth, but that, rather, the stage itself is animated, part of a larger living entity, Gaia, composed of the biosphere together with the “nonliving” components that shape, respond to, and cycle through the biota of Earth. Yes, life adapts to environmental change, shaping itself through natural selection. Yet life also pushes back and changes the environment, alters the planet. This is now as obvious as the air you are breathing, which has been oxygenated by life. So evolution is not a series of adaptations to inanimate events, but a system of feedbacks, an exchange. Life has not simply molded itself to the shifting contours of a dynamic Earth. Rather, life and Earth have shaped each other as they’ve co-evolved.

"The truth is, despite its widespread moniker, Gaia is not really a hypothesis. It’s a perspective, an approach from within which to pursue the science of life on a planet, a living planet, which is not the same as a planet with life on it—that’s really the point, simple but profound. Because life is not a minor afterthought on an already functioning Earth, but an integral part of the planet’s evolution and behavior. Over the last few decades, the Gaians have pretty much won the battle.

***

"We’re realizing that it is not enough to determine basic physical properties of a planet, its size and distance from a star, in order to determine its habitability. Life itself, once it gets started, can make or keep a planet habitable. Perhaps, in some instances, life can also destroy the habitability of a planet, as it almost did on Earth during the Great Oxygenation Event (sometimes called the oxygen catastrophe) of 2.1 billion years ago. As my colleague Colin Goldblatt, a sharp young climate modeler from the University of Victoria, once said, “The defining characteristic of Earth is planetary scale life. Earth teaches us that habitability and inhabitance are inseparable.”

***

"Organisms and species do not have cosmological life spans. Gaia does, and this is perhaps a general property of living worlds. Influenced greatly by Lovelock and Margulis, I’ve argued that we are unlikely to find surface life on a planet that has not severely and flagrantly altered its own atmosphere. According to this idea, a planet cannot be “slightly alive” any more than a person can (at least not for long), and an aged planet such as Mars, if it is not obviously, conspicuously alive like Earth, is probably completely dead.

***

"When we stop thinking of planets as merely objects or places where living beings may or may not be present, but rather as themselves living or nonliving entities, it can color the way we think about the origin of life. Perhaps life is something that happens not on a planet but to a planet: It is something that a planet becomes.

***

" The earliest stages of life may be extremely vulnerable, and there may be a point where, once life becomes a planetary phenomenon, enmeshed in the global flows that support and fuel it, it feeds back on itself and becomes more like a self‐sustaining fire, one that not only draws in its own air supply, but turns itself over and replenishes its own fuel. A mature biosphere seems to create the conditions for life to continue and flourish.

***

"The scientific revolution has revealed us, as individuals, to be incredibly tiny and ephemeral, and our entire existence, not just as individuals but even as a species, to be brief and insubstantial against the larger temporal backdrop of cosmic evolution. If, however, we choose to identify with the biosphere, then we, Gaia, have been here for quite some time, for perhaps 3 billion years in a universe that seems to be about 13 billion years old. We’ve been alive for a quarter of all time. That’s something."

Comment: I agree.