What Once-in-an-Eon Event Gave Earth Its First Plants Around 1.5 Billion Years Ago? — Here’s What Scientists Believe

On today’s planet, you can see plants everywhere. A moss on a rock, grass in parks, tall trees in forests, and even algae on ponds and oceans. But Earth was not always like that, and there was actually a time over 1.5 billion years ago when it had no plants anywhere.

The land was just barren and made up of rocks and dirt. Back then, the only life was in the waters, a thin layer of microbial organisms. However, did you know that scientists think that the origin of all plants could be traced back to a once-in-an-eon event more than a billion years ago? Let’s dive deep into the history of this planet to explore more.

The Day a Cell Swallowed a Bacterium and Kept It

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Long before there were any trees or grass, the oceans on the planet were filled with simple microbial lifeforms like bacteria. Among these were cyanobacteria. This is a tiny organism that can perform photosynthesis, producing oxygen by using sunlight, carbon dioxide, and water to make sugar and then releasing the oxygen as a byproduct.

Then, at some point around 1.5 billion years ago, a eukaryote or a larger single-celled organism did something that it had probably done many times in the past. But there was something different this time; the cyanobacterium it had swallowed survived. It likely ate it as food, but this time the bacteria were not digested but instead formed a tight partnership with the host.

The cyanobacterium provided the sugar and the oxygen from photosynthesis, while the host cell gave protection and nutrients to the bacteria. Then, over time, slowly, the cyanobacterium became a permanent part of the host cell, losing some of its genes and becoming a new kind of structure that will later become the chloroplasts in plants we now observe. This whole process is often referred to as endosymbiosis.

Read more: Paleontological Research Institution | Unilad

Why Scientists Call It a “Once-in-an-Eon” Event

The Evolution of early Plants

Studies suggest that this process seems to have happened only once in the ancestor of a group called Archaeplastida, which includes algae and land plants. Their chloroplasts could all be traced back to this single merger between a host cell and a cyanobacterium.

This is why sometimes, scientists refer to this moment as once-in-an-eon, because if that one ancient eukaryote had digested this cyanobacterium as it probably always had done, there might never have been any forests, any grasses or flowers, and the evolution of animal species may have also been completely different, including us, humans.

Author's Final Thoughts

A single-celled organism ate a cyanobacterium, but instead of it becoming a meal, they lived in partnership, which over time gave us plants. So, whenever you see a big tree, a small patch of moss on rock, or algae floating in water, you’re probably looking at a result of this once-in-an-eon event, an ancient partnership that set the stage for almost every ecosystem that we could see today.

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