Plate Tectonics and Evolution

The theory of plate tectonics has been just as revolutionary as Darwin’s theory of evolution in furthering our understanding of the world we live in. In essence, plate tectonics is the idea that Earth’s outer shell is composed of plates akin to giant puzzle pieces, which glide over the planet’s hot inner mantle. Whether they’re colliding, diverging, sliding, or diving beneath one another, tectonic plates are always on the move. This movement is driven by the heating and cooling of rock in a process called convection, where molten material close to the core rises while cooler mantle rock sinks back down. The result is a sort of conveyer belt effect that keeps the plates moving. The origins of continents, oceans, mountains, volcanoes, earthquakes, and many other incredible things can be explained by plate tectonics.

But what about life? Regardless of how it first came to be, it’s clear that Earth’s ocean played the most crucial role in supporting it, especially early on; but without plate tectonics, the ocean may have been too stagnant and lacking the vital elements needed to encourage life to grow. In her article covering the research of plate tectonics and evolution, writer Rebecca Boyle describes the finding of microbial mats within the depths of the Mariana Trench (to which the location itself is a result of the movement of the Pacific Plate). The existence of these microorganisms in such a harsh environment gives us insight on how the first self-replicating cells might have grown and thrived on early Earth. These cells would have needed chemical compounds from the planet, which might have been difficult to get without the processes of plate tectonics. This is because plate movement delivers these compounds through a process called serpentinization, where previously trapped water gets released from the plate as the plate gets dragged down into the mantle and heats up. These water bubbles make their way to the surface, transforming the physical properties of the mantle as it does so. Without this process, as Boyle states, the life-giving nutrients beneath the surface of the planet would stay trapped and wouldn’t be able to foster life as a result.

Of course, underwater microbes and lifeforms like humans are very different, and it’s this development of simplistic to complex that plate tectonics may have had more of an effect on. Geologist Robert Stern suggests that life might not have needed plate tectonics in order to begin, but likely would have needed it to evolve in such intricate ways. It’s not certain whether the processes of plate tectonics themselves created the continents, but they absolutely affect them, and it’s this force of constant change that Stern argues the importance for. As the plates move, the land changes: mountains are formed and continents break apart or reconnect, isolating or integrating different species. This, Stern says, drives natural selection and competition for both land and marine communities alike and forces them to adapt to survive. Such environmental pressures can also cause extinction, which further opens up competition space. To illustrate his point, Stern asks us to compare two nearly identical hypothetical planets (with oceans, land, etc) over hundreds of millions of years, with the only difference being that one has plate tectonics and the other lacks it. He speculates that we would see a clear difference in the complexity and resilience of evolved life in the Earth-like planet. So without this added layer of evolutionary challenge, it’s hard to say whether we would have emerged as the species we are today.

The theory of plate tectonics has helped us understand the planet we call home in so many ways, but there’s still so much we don’t know about it, too; let alone other planets and other potential lifeforms. We only have one sample, Earth, so it’s hard to infer what life might be like elsewhere. But if there is life out there, it very well could be on a planet like ours: a planet with an ocean, land, and plate tectonics.