Life had a small surprise just after the end-Cretaceous mass extinction

Earthworms survived C-T extinctionYou may have felt really lonely walking the face of Earth. Until you looked closer. [Btw: who needs peer-reviewed literature when you've got the annual festival of presentations at the Geological Society of America?]

Understanding Earth’s historic mass extinction events is crucially important considering the current biodiversity crisis. But once you start reporting from the front of paleoecology and paleoclimatolgy there’s no end to it. Isn’t it strange, after all these millions of years, everyday there is something new?

Three days ago we looked at the ecological aftermath of the Permian-Triassic mass extinction – the reappearance of reef systems. Today researchers from the University of Colorado at Boulder report on the aftermath of the Cretaceous-Tertiary mass extinction – the one that wiped out the dinosaurs and even those cheerful abundant ammonites.

It is an aftermath that is of particular interest to us, because [considering the PETM extinction 10 million years later was mostly marine] we are ourselves a product of it. Life on Earth moved to a phase were birds flock the skies, mammals rule the land (and even oceans) – …and after 66 million years one primate puts everything in place to once again end one of our planet’s geological chapters.

The Cretaceous aftermath, page 1

Anyway, it’s not the last page of this chapter we’re discussing, it’s the first. It’s in a way imaginable to walk across the face of the Earth a few weeks after that hard-to-trace asteroid struck.

It must have looked miserable. No one is sure, but think of something as dramatic as pitch-black skies, blown over smouldering forests, swamped coastlines, dry river beds, and depending on where you look lots of dead, wounded and even unharmed animals – some of whom must have thought it a real feast, for as long as carcasses remained.

It’s much harder to imagine coming back in a thousand years or so. We know a nice chunk of Earth’s biodiversity did survive, however these plants and animals had to regroup and balance out into entirely new ecosystems. It must have still been a desolate place – and you can be sure, walking the soil, there was nothing big and scary that you would encounter.

If you kneeled down however you’d have a chance to see something familiar to cheer you up: an earthworm – right about how you know them.

The Colorado researchers have found fossil remains of its burrows very close to the Cretaceous-Tertiary boundary, within a few thousand years. Evolution isn’t that fast – coral creatures need 1.5 million years to ‘re-evolve’ from a distant relative after they die out. Worms it seems were survivors, always there. Think of that next time you see one trying to cross a bicycle lane – and help it across.

© Rolf Schuttenhelm | www.bitsofscience.org

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