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A new research revealed that tiny creatures living in complete darkness have once dominated our planet

Posted July 18, 2018

We tend to think that dinosaurs were dominating life on Earth for a long time. However, that would be a wrong statement. In fact, you cannot say that about any land-walking creatures, including humans. A new study from the Universities of Edinburgh and Aberdeen suggests that tiny creatures that lived in the dark underground or in the sea were the dominant life forms on Earth for much of the planet’s history.

Before plants took over, tiny microorganisms living in complete darkness under water or ground were dominant in our planet by weight. Image credit: 0x0077BE via Wikimedia

Evolution of life on Earth is a fascinating subject that has attracted scientific attention for a very long time. We don’t know for sure how life in our planet looked several million years ago, but we can try to figure it out by the signs that it left behind itself. Now scientists think that for from about 2 billion years ago until 400 million years ago, tiny microorganisms, including bacteria, were the most abundant forms of life on Earth, weighing around 10 times as much as all other life on the planet combined. This is what scientist figured out by analysing data on the current make-up of life on the planet to work out how this has changed over billions of years.

Our planet is ready to tell its history to us. The best example is that rocks have records of chemical composition changes of the atmosphere and oceans through time. Scientists can use this information to estimate condition changes through the time to see what kind of life would thrive in a particular time. Life on Earth probably started 3.8 billion years ago with single-celled organisms while dinosaurs appeared 230 million years ago. Earliest mammals appeared even later. And so it allows scientists to estimate that tiny microorganisms living in the dark were dominant species on Earth for a long time until plants began to spread across the land.

Plants are now dominating the planet. Yeah, we are killing them at an alarming rate, but their combined weight is still the greatest, accounting for about 500 billion tonnes of carbon. Bacteria are still in the second place, contributing to the planet with a combined weight of about 100 billion tonnes of carbon. Dr Sean McMahon, one of the authors of the study, said: “Prehistoric life on Earth was like an iceberg – most of it was found below the surface. The total mass of life on the planet was far smaller before plants took over”. Humans are nowhere near domination in terms of our weight, but at least we are smart enough to figure out the lineage of the history of life on Earth.

We are still learning about our planet – we still don’t know so much. Plants are dominant right now, but before them it was tiny microorganisms living in complete darkness. Up until recently the biggest and most important habitat was underground.


Source: University of Edinburgh

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