Pliocene

The planet has passed a disturbing landmark, a marker on a continuing highway to climate disruption. On May 9th, the NOAA and the Mauna Loa observatory reported that atmospheric CO2 levels touched 400 parts per million. Before humans started burning fossil fuels, they were around 280 parts per million. Mauna Loa measurements of carbon dioxide. From http://keelingcurve.ucsd.edu/   The last time atmospheric CO2 was at 400 parts per million was during the ancient Pliocene Era, three to five million years ago, and humans didn’t exist. Global average temperatures were 3 to 4 degrees C warmer…
A diagram of how the skeletons of Australopithecus sediba came to be preserved in the Malapa cave deposit. From Dirks et al, 2010. A little less than two million years ago, in what is now South Africa, a torrential downpour washed the bodies of two humans into the deep recesses of a cave. Just how their remains came to be in the cave in the first place is a mystery. Perhaps they fell in through the gaping hole in the cave roof just as hyenas, saber-toothed cats, horses, and other animals had, but, however the humans entered the cave, their bones ultimately came to rest in a natural bowl…
The fail whale comes to rest; the decomposing body of a gray whale is host to a diverse array of scavengers and other deep sea organisms. From Goffredi et al., 2004. In the deep sea, no carcass goes to waste. Platoons of crabs, fish, and other scavengers make short work of most of the bodies which come to rest on the sea bottom, but every now and then the carrion-eaters are presented with a rotting bonanza; a whale fall. Muscle, viscera, blubber, and bone; it all gets broken down, but it takes so long that the whale carcass actually provides a temporary home for a variety of organisms which…