Evolution: how life evolved the Earth (Evolution)

by David Turell , Friday, November 18, 2022, 15:33 (734 days ago) @ David Turell

A very poetic and dramatic essay showing how the appearance of life totally reshaped the Earth:

https://aeon.co/essays/the-insight-of-darwins-work-on-corals-worms-and-co-evolution?utm...

"I want to start with a proposition: if Earth had never come alive, it would be a profoundly different world. Conversely: the planet of today has, to a remarkable extent, been made what it is by the activities of lifeforms. Over the course of the planet’s long history, a history that extends back more than 4.5 billion years, lifeforms have shaped the rocks, the water, the air, even the colour of the sky. A Never-Life Earth would not even have as many different kinds of minerals.

"This is the portrait painted by the modern science of life and Earth, a fusion of biology and geology that seeks to understand all the planets that Earth has been, and that unites such apparently unrelated fields as the study of bacterial metabolism with the physics of atmospheres. The central observation of this undertaking is that, over time, lifeforms have profoundly altered the fabric of this planet, and this, in turn, has altered the circumstances in which lifeforms evolve.

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"Darwin, of course, is famous for his work on evolution. His book On the Origin of Species (1859) laid out a wealth of evidence that evolution occurs, and proposed a mechanism – natural selection – for how it does so. Although much has been learned since, and many of his ideas have been extended, corrected or refined, the Origin remains the founding text of modern biology, and is the pinnacle of Darwin’s work. But Darwin’s first scientific monograph and his last – the two bookends of his thoughts, so to speak – were both about how animals have, over vast spans of time, transformed the landscape.

"These two works of biogeology – one on coral reefs, the other on earthworms – were, as far as I know, the first detailed studies of the subject ever published. On casual inspection, they appear to be unrelated undertakings, just part of Darwin’s long and eclectic list of interests, along with barnacles, orchids, carnivorous plants, peacocks’ tails, the emotions of humans and other animals, the volcanoes of South America, and so on. This impression is enhanced by the fact that the two works differ greatly in style and were published almost 40 years apart – The Structure and Distribution of Coral Reefs appeared in 1842, while his book on earthworms, The Formation of Vegetable Mould, Through the Action of Worms, with Observations on Their Habits, came out in 1881, about six months before he died.

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"Long before animals or plants evolved, moreover, the planet was being sculpted by much smaller lifeforms – bacteria and archaea. (Of these, bacteria are far better known. That’s because archaea were not identified until the 1970s. Seen through a microscope, archaea superficially resemble bacteria – both are small and tend to take shapes such as rods or spheres. So it was not until the development of molecular tools that it became clear that the two groups are distinct.) I will not enumerate all the effects these lifeforms have had, as it would take too long. Instead, I will give just two examples of their impacts. First, certain species of archaea are responsible for the biological generation of methane, a greenhouse gas, which warms the climate. Second, no conversation about the impacts of lifeforms upon the planet would be complete without mention of the cyanobacteria. These lifeforms, formerly known as blue-green algae, are, in my view, the most important lifeforms in the history of the planet. At the time they evolved, more than 2.3 billion years ago, Earth had no oxygen molecules in the air to speak of. Instead, all the oxygen atoms were tied up in the water and the rocks. Cyanobacteria evolved to use the radiant energy of the Sun to split water molecules apart, a process that roughly halfway through the history of Earth would result in an atmosphere that contained oxygen molecules.

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"...if we are distinguished by the scale and speed of our impacts, we are also distinguished by our awareness. As far as anyone can tell, humans are the only lifeforms that have ever been able to study the world and know what we do – and that brings opportunity. Perhaps, together, we can reduce our impacts and develop a new ethos of planetary care.

"I would like to end on a personal note. Contemplating the entwined histories of life and Earth has changed the way I see the world. It has heightened my interest in all lifeforms, no matter how humble, and it has enhanced my sense of connection to the air, the water, the rocks. I find it majestic to think that the air I breathe and the rocks I tread have been shaped by countless lifeforms that lived and died ages ago. To me, this view of life and Earth is poignant, beautiful, and grand."

Comment: a beautifully written essay, extremely long, containing a biography of Darwin's magnificent research in many directions. It clearly shows how the appearance of life totally transformed the Earth.