In Ages Long Ago…

Not the opener to “Voltron”, but the latest synthetic palaeo-news.

First, appropriately enough, the first tracks of the First Crawling Things…

Found: The first ever animal trails …reported by “New Scientist”, some rock-hounds have discovered 565 million year old anemone trails. Well… they look like anemone trails at least. Older ‘trackways’ are known, but they’re not obviously animal tracks since things like gas-bubbles under algal mats can leave similar markings. These are the real deal.

But why then? The Ediacaran/Vendian came just after the last Big Glaciation (Snowball Earth) and a multitude of squishy, shelly Things appeared and left fossils. Why not earlier?

The next news item answers that…

First breath: Earth’s billion-year struggle for oxygen
…seems cyanobacteria, the oxygen-making variety, didn’t appear until c.2.7 billion years ago, took 300 myr to oxygenate the air, then collapsed during the subsequent Ice Age, caused by oxidation of the methane greenhouse of the time. The first series case of climate change due to Life’s by-products, perhaps. An earlier one might’ve been caused by the methanogens themselves, who warmed the Archean Earth.

After the end Archean Ice Age, the Earth languished in an epoch of smelly oceans – hydrogen sulphide and sulfate dominated – but finally something shifted, probably the Greening of Rodinia about 800 mya. This mass erosion event caused by lichens and terrestrial algaes, set the Earth for the Snowball Earth events and the subsequent explosion of animal Life. Or so the story goes as told by Nick Lane. Like all such Proterozoic Tales, there’s a lot we just don’t know.

The implications are interesting. Where did the oxygen making bacteria come from? Could they have drifted in from Venus as its oceans were wafted into the stratosphere and photolysed? That’s my pet theory – we’re all Venusians. Of course Panspermia implies all the suitable solar planets and moons are really one common biosphere.