Ben Martynoga joins us today to consider the importance of water to life on earth.
Planet Earth or Planet Water?
You drink it, shower in it, cook in it, flush it down the toilet. You only notice it when you’re thirsty, or getting soaked by an unexpected downpour. Water: you probably take it for granted.
But that’s a mistake. Because water is everything. Water is the reason you’re sitting here reading these words.
Fact 1: Earth is the only planet in our galaxy where we’re certain liquid water exists on the surface.
Fact 2: Earth is the only planet where we know that life exists.
Fact 3: Facts 1 and 2 are connected. Because life’s story – which is also our story – is all about water.
Life began in water, nearly four billion years ago. Most scientists think this happened in an incredibly unpleasant place – inside a boiling hot, high-pressure deep-sea ‘hydrothermal vent’.
Eventually, from this seething cauldron, the first living cells emerged: microscopic blobs of living matter, each wrapped in a wafer-thin skin called a membrane. To this day, all life is based on cells (find out why in Explodapedia: The Cell).
Those first cells were tiny and fragile, but they had everything they needed to stay alive. Each contained a set of genes; an operating manual, written in DNA (see Explodapedia: The Gene for more). And, most crucially, each cell could multiply itself, by growing, printing out a new copy of its genes, then splitting itself in two. And multiply they did – like crazy, filling the world’s oceans with gigantic swarms of tiny living beings.
For three-quarters of Earth’s history, all living things were single-celled. Then, about half a billion years ago, some cells started working together to create bigger bodies.
The first animals were squidgy and shapeless, a bit like sea sponges. But they also happened to be YOUR ancestors! Then, thanks to the creative power of evolution (to read the full, true story, Explodapedia: Evolution publishes November 2023!), their descendants gradually turned into fish, with most of the organs and that your body still relies on today: eyes, muscles, hearts, backbones, brains, tongues, bums and more.
You might’ve heard that some of our fishy relatives eventually slithered out of sea, leaving the water behind to start a new life on dry land. It’s a good story, but it’s not strictly true. The ‘leaving the water behind’ part isn’t, anyhow. Because cells must never, ever dry out. Water is the stuff that keeps life’s chemical reactions ticking over. So, those fish had no choice but to take the water with them – inside and around their cells.
If you’re in any doubt about how essential water is to life, just take a look in the mirror. You look quite solid, but your body is actually about 65% water. Even about a quarter of the weight of your bones is water. The brain that’s reading these words is up to 85% water! Why? Because you’re entirely made of cells – about 30 trillion of them. And when they’re out of water, cells die.
Here’s something else to ponder: if the ‘dry land’ we live on really was ‘dry’, we wouldn’t be here. All land-based life forms rely on plants (even if you eat meat and dairy, farm animals eat plants). And plants need earth. But if that earth dries out completely, it turns to dust, and all the plants die.
So maybe we should start calling our lovely home planet ‘Water’ instead of ‘Earth’?
Maybe then we’d might stop taking water for granted. We’d remember to treat it like the irreplaceable, life-sustaining stuff that it is? We’d stop wasting it and pumping pollution into rivers and seas. Because we’d all remember once and for all that we are watery beings on a watery planet. We came from water and we will, forever more, need water.
Ben Martynoga is a biologist and writer, based in Cumbria. You can read more about everything in this blog, and much more besides, in the brand-new non-fiction book series, Explodapedia, stunningly illustrated by Moose Allain.
We are very grateful to Ben and the team at David Fickling for joining us to celebrate NNFN2023.
Three Explodapedia titles, ‘The Cell’, (ISBN: 9781788451918), ‘The Gene’ (ISBN: 978-1788452458) and ‘Evolution’ (ISBN: 978-1788452502) are currently available from David Fickling Books.