Our planet, shaped by life

By | November 18, 2022

Olivia Judson writes:

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.

Yet the idea that lifeforms might alter Earth is not new.

In his encyclopaedic Histoire naturelle, générale et particulière (1749), the French natural philosopher Georges-Louis Leclerc, Comte de Buffon remarked on the prodigious heaps of fossil shells that make up many rock formations, and stated that substances such as limestone, chalk and marble, despite their inanimate nature, are the result of the activities of lifeforms. In Hydrogéologie (1802), Buffon’s protégé Jean-Baptiste, Chevalier de Lamarck took the point further, suggesting that the activities of lifeforms had shaped the mineral composition of Earth. But as far as I have been able to discover, the person who first attempted to measure the changes that lifeforms have wrought, and who had the clearest sense of why they have an impact, was none other than Charles Darwin. In thinking about the Anthropocene – the age of human impacts upon Earth – the lessons of his work have never been more important.

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. [Continue reading…]

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