The end is nigh, 2.5 billion years ago

By Minda Berbeco on June 4, 2013

Through my work in the sciences, I've found myself in some pretty cool places. Researching urban trees in Cuba (a clipboard in one hand, a cigar in the other), machete-ing my way through a tropical rainforest while being hunted by wild pigs, sipping lattes for hours and hours and hours and hours while writing all of that work up (a caffeine drip really would have been more helpful). But nowhere was as cool and interesting as my most recent position at a paleontology museum here in California, because let's be serious, dinosaurs rule.

In case you are wondering, yes it's just about as awesome as you'd think it would be. There are millions of fossils there. Warehouses. Multiple warehouses of bones. Cabinets, shelves and boxes filled with toes, tibias, skulls, teeth.

You need a wolf jaw from the La Brea tar pits? We've got those.

Mammoth skulls? Of course. Mastodon? Well, you can't have a mammoth without a mastodon, it's like having an incomplete set.

T-Rex teeth? D'uh. Diplodocus pelvis? Archaeopteryx? Pterodactyls? Sure!

And of course petrified wood and leaves and shells and racks and racks and racks of microfossils plated on slides.

To say the least, I'm a tiny bit impressed.

Sitting in the museum with overflowing boxes of fossils you have to be amazed at the abundance of life, and then you have to ask where it's all come from and where is it going?

Most of all, though, you have to stop and think, where and when did it all start? What was the beginning and what came before? Before the toes and the hips and the bones, before the leaves and the bark, before even those tiny little shells and microfossils.

Before all of them, everything that is warehoused in the museum dating back millions of years….before all that, what was there? There was nothing.

Well, that's a lie. There was something, there was lot's, I suppose. It just wasn't really nearly as impressive.

You see over 2.7 billion years ago the earth was way different (1). I mean the atmosphere was different. And I'm not talking LA on a smoggy day different. I mean there was no oxygen in the air. So everything that was living on earth couldn't be oxygen-lovers like us. No instead anaerobes ruled (those are organisms that live without oxygen) living in thick microbial mats.

These microbes were living the good life. They were slow to grow, slow to divide, slow to do everything, because without oxygen, organisms are actually not incredibly efficient. But what does it matter, living too slow a life? Who's gonna care?

But then cyanobacteria arrived on the scene, which were the first oxygen-making bacteria.

The other bacteria were like, "whoa, way weird", but mostly it was ok because the oxygen they produced got sequestered through chemical reactions and nothing really changed too much for the anaerobic microbes (2). Life was still good. As good as it can be for a methane farter.

But then something happened – and it's not really known what – and oxygen started accumulating in the atmosphere. The bummer thing is that oxygen is actually way toxic for you if you are an anaerobic bacterium. So essentially cyanobacteria became these horrible polluters, releasing toxic oxygen into the atmosphere, and antagonizing the anaerobic bacteria (3).

Can you imagine the fallout? Anaerobic bacteria running through the streets screaming, "The end is near! The end is near!" That is if there were streets, which there weren't, and bacteria could run and scream, which they can't. So, this is really a metaphorical running and screaming through the streets.

And then things got even worse. I mean worse for people like me who would have loved that toasty pre-photosynthesis, methane-rich environment (aside from the not being able to breathe bit). As oxygen rose in the atmosphere, methane went down and since methane is a greenhouse gas which helps warm the earth, the earth got way cool. I mean really cold. This is what people call "snowball earth", so you can guess how cold I'm talking. And it lasted forever….until it ended, eventually.

So what was the fallout of the great oxidation event? Well, life. I mean life as we know it. It took a while, a couple billion years, and earth was turned into a giant snowball, but eventually oxygen rose to near-modern levels, and we start to see oxygen loving organisms developing in the seas (1).

From there came toes, and noses, and hips and wings and all the things that we know and love and stock into museums to hide away and study. Along came life. You see, it turns out that all that life on earth that we know and love didn't start at the beginning as we like to believe. It started, with the end. The end of days.

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