Friday, February 6, 2009

From cold to hot: more cool palaeo stuff.

You've heard about the Ice Ages. Ten thousand to a million years ago. Glaciers, mammoths, Raquel Welch in a fur bikini. Pshh. Big deal. A few big glaciers and what did we get out of it? Igloos? Let's go back to the real ice age. The Cryogenian period. 850-630 million years ago. The Earth got so cold that it might have frozen completely over. A global hockey rink.

As cold as it was on the surface, things were happening underneath. A new paper announces the discovery of the oldest animals yet, sponges that date back 635 million years. Fossil imprints weren't actually found, rather there were deposits of steroids (Barry Bonds was alive back then?) in the rock left behind from the sponges' tissue. It appears that all that cold may have had a hand in changing the chemistry of the oceans, introducing  more oxygen in the system, allowing single-cell organisms, who had already been around for a couple billion years, the energy to evolve into complex multicellular organisms.

Credit: Copyright Jason Bourque, University of Florida

I can't feel my toes. Let's put our shorts on and hop in the time machine to the Paleocene epoch, 65.5-55.8 million years ago, right after that big rock plowed into the Yucatan and finished the dinosaurs off. After the evolutionary party that was the Mesozoic, the earth had had about enough of thunder lizards and wanted peace and quiet while it slept off its hangover. The mammals, which had evolved while trying not to get stepped on by dinosaurs, now had the run of the place. The world was like a kid's TV show, populated by small, furry creatures. That's what I always thought, anyway.

Like anything else, just as you think it's safe.... For one thing, it was hot as fuck, smoggy from forest fires and muggy. Little mammals still had to watch out, because there were snakes 45 feet long that could swallow something as big as a cow. Stalking the underbrush were sebecosuchans; big, fast crocodiles that could run like hell. Nervous and sweaty, our ancestors in the Paleocene didn't have the post-dinosaurian kumbaya that I thought.

A few other recent goodies: New evidence that proto-whales with feet still gave birth on land, a revelation on the origin of claws in arthropods, and our ancestors had jaws of steel.

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