Hello I'm Justin Rollout. Welcome to episode 2 of a geochemical history of life on Earth here on the BBC World Service.

I'm exploring how our planet chemistry made life possible and how life has transformed our planet's chemistry, including what we humans are doing to

the atmosphere right now. This week we venture into the longest and darkest period in our planet's history, the pre-Cambrian.

It's a voyage that spans three and a half billion years,

almost 90% of the time that life has existed.

It's a world populated by bacteria and our most primitive microscopic ancestors,

but these tiny creatures revolutionized the Earth's chemistry by producing the first oxygen.

And in doing so, they laid the foundations for life as we know it today. So I've come to the Natural History Museum in London. I'm in the Hincse Hall, the main

entrance to the museum underneath this fabulous kind of blue whale skeleton. I'm a meeting Dr. Imran

Welcome. But thank you very much indeed and it's so stunning here and also so

busy, so many people back after the pandemic.

It's fantastic to have so many people back in looking at our lovely

fossils. There's more here than just fossils. You're just obsessed with the proof.

That's what I'm obsessed with.

Imran researches the origin and early evolution of life for the museum and he's invited me to see a remnant of the most catastrophic development in that early evolution.

So just walking into one of the alcoves on the side of the hall and there's this huge

huge lump I would say it's a rock but it doesn't actually look like a rock you've cut

through it and it's kind of looks like a bit of modern art and there's layers of

kind of reddish banded with darker material and it looks a little bit like

the atmosphere of Jupiter from telescopes and it's huge it is 2.5 tons and how old is 2.6 billion years old that is more than half as old as the earth itself.

Really, really old and really big.

And you do wonder how they managed to get this.

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