The animated sci-fi series Scavenger’s Reign takes viewers to the strange planet of Vesta, where womb-like sacks hang from trees and floating fluff balls stick to skin. It’s a hostile and merciless world, and the show’s protagonists — five stranded space travelers — have to fight off danger after danger as they journey towards their fallen ship.
Contributing to the strange otherworldliness is the fact that the planet itself sometimes feels as alive as its organisms. That’s intentional. “I was thinking a lot about the Gaia theory with this planet, of just that everything on it is sort of a bacteria,” said co-creator Joe Bennett to Collider. “It's all one living organism and even the humans are sort of an invasive bacteria, but they're just a part of everything.”
While humans are, of course, not bacteria, nor “invasive,” the idea that all living things on our planet work together has long been debated in the earth science and ecology worlds. The Gaia theory (or the Gaia hypothesis, as it’s often called) was invented back in the 1970s by chemist James Lovelock and biologist Lynn Margulis. The theory’s central idea is still debated amongst philosophers of science, who might sound a bit more like Bennett in their conversations than other scientists. But in the ecology world, Gaia evolved into more evidence-based perspectives about the interconnectedness of Earth and the life within it, Bruno Travassos-Britto, an ecologist at the University of Toronto Mississauga, told Inverse. And Lovelock never suggested that the Earth was alive (even though his naming the hypothesis after a goddess is a little confusing). Rather, he proposed that Earth might have life-like properties — in particular, self-regulation.
According to the Gaia hypothesis, the actions of living things help to self-regulate Earth’s non-living things, like the atmosphere and ocean, and that life acts in ways to keep the planet’s environment habitable. For example, it’s the idea that trees draw down carbon dioxide to maintain the planet’s temperature not for their own individual benefits, but because it helps maintain livable conditions for a wider community of organisms.
The concept is meant to explain why and how Earth’s conditions have remained viable for life for so long (3.7 billion years!) despite massive perturbations (like asteroids). We tend to take it for granted that the planet has stayed habitable over all that time, says Toby Tyrrell, an earth system scientist at the University of Southampton and author of On Gaia. “But there's lots of reasons why that is actually really surprising.”
Does the Gaia hypothesis explain how Vesta maintains its life-sustaining conditions? Maybe! “It's not impossible that in a planet evolving things, it will evolve an organism who has a clear goal of preserving the world as it is because it wants to keep life stable,” Travassos-Britto says. But since the hypothesis hinges on working towards an end (i.e. organisms act a certain way in order to maintain livable conditions), we’d need more information about the planet’s conditions, what’s considered livable for the creatures, and how their actions affect those conditions to know for sure.
What about in real life, here on Earth? While the idea still floats around, and has some interesting components worth considering, “it just doesn't really stack up” as a way to explain how the Earth’s systems work, Tyrrell says.
There are some examples where feedback loops between living and nonliving things do help to maintain planetary conditions. For example, photosynthesis in plants and algae fills the atmosphere with oxygen, which is essential for the survival of most organisms. In this case, plants are helping to self-regulate planetary conditions. But the real question is whether plants are performing photosynthesis in order to keep the planet habitable, or if they’re doing it for their own survival.
Scientists argue that it’s likely the latter, because life also functions in ways that harm its ability to thrive. A long time ago, the atmosphere lacked oxygen, until unicellular organisms evolved that could metabolize oxygen. In a short few million years, the atmosphere shifted to contain lots of oxygen, which was toxic to most living things at the time. The change caused a massive extinction event, wiping out almost all living organisms. “Where is the homeostasis there?!” Travassos-Britto says.
It’s tempting to compare Earth’s properties to those of an organism, to imagine that Earth could also self-regulate for survival, like a living thing does — especially because it can provide some comfort as we face the climate crisis. A fever in a living thing indicates that the immune system will help to stabilize the body; a fever on the planet suggests no such thing. “The earth will not care,” says Travassos-Britto. “It’s not fighting to keep a homeostasis to preserve the species.”
There are so many fundamental differences between Earth and living organisms that making that comparison is “confusing” as a model for scientists, and thus not very useful, he says. “Maybe Gaia is also a very complex system, like an organism. But I think this is the extent of the usefulness of the Gaia model.”
Still, the Gaia hypothesis continues to be influential in scientific fields. Back in Lovelock’s time, it wasn’t well accepted that life could impact the planet’s functions, says Tyrrell. Whereas now, thanks in part to the ideas in the hypothesis, “there’s no question life has had a major influence on the nature of the environment over time.” And one of the prominent theories in ecology today — ecological succession — posits that life leads to other life, which shares some concepts with the Gaia hypothesis.
That life might influence the planet to keep itself alive is a “beguiling idea,” says Tyrrell. “People want to think it’s true.” There are some scientists who still discuss it. But in many cases, serious discussions of the Gaia hypothesis are happening over animators’ desks as they invent strange, self-regulating alien worlds, which may exist out there, somewhere.
