15.5: Life and Earth as One?

By way of offering a theme to these pages, I’d like to draw inspiration from an uncharacteristic and outspoken scientist, English scientist James Lovelock (1919–2022). In the 1970s, Lovelock wrote a very controversial book called Gaia: A New Look at Life on Earth (Lovelock 1979). The book offered a speculative extension of work he started with NASA in the 1960s, in which he proposed that if a planet’s atmosphere was out of chemical equilibrium, then it probably harbored life. By his analysis, life was not present on Mars because its atmosphere appeared to be in a state of equilibrium (Lovelock 1965). His Gaia book took things a bit further—too far for some scientists at the time. Lovelock presented circumstantial evidence that life didn’t just inhabit Earth, but that Earth itself was a living organism. He called this idea the Gaia Hypothesis. In later years—and admitting that this first work was “poetic”—Lovelock modified the Gaia Hypothesis to state that the evolution of life and Earth’s environment occurred “as a single, tightly coupled process, with the self-regulation of climate and chemistry as an emergent property” (1989).

This coevolution of life and Earth’s environment forms the basis of a relatively new field of study known as geobiology, the study of life’s interactions with the Earth and their evolution over geologic time. Lovelock calls it geophysiology, but they are essentially the same thing. At the heart of geobiology are the ways in which life has shaped Earth and vice versa. Much of what we have talked about in this chapter falls under the heading of geobiology. In the introduction to their textbook Fundamentals of Geobiology, Knoll and coauthors (2012) credit Lovelock’s Gaia Hypothesis for grabbing “the attention of a broad scientific community.” While the “strong” version of Gaia—that life regulates Earth for its own survival—receives less scientific support, there is now support for and attention given to the significant role of organisms in regulating at least some aspects of the Earth system. Of course, having read this book this far, you already know that.

Lovelock’s Gaia Hypothesis provided a focal point for Earth systems science—the study of the interactions of the spheres introduced in Chapter 1—and brought greater attention to interdisciplinary studies of the Earth system as a whole. Of course, there is no greater need for this approach than today, as we increasingly recognize the negative impacts of human activities on the biosphere. Lovelock was vocal about climate change, too, but that is a story for another chapter.

Hopefully, this sweeping and admittedly imperfect summary of the history of life and our planet has provided a thoughtful perspective for understanding the world ocean and the organisms that inhabit it. We are products of our history—descendants of a drama in progress, if you will—the story of life on Earth. Next time you’re roaming around the neighborhood, camping in the woods, rock-climbing in the desert, or visiting the tidepools, take a moment to consider the life-forms that surround you. You’re here because they’re here. To borrow a quote from a famous American poet, “And that has made all the difference” (Frost 1923; first published 1916).