seven cervical vertebrae for starters. We've inferred quite a lot about the Cretaceous extinction from the fossil record and particularly from the strange observation about Iridium made by Luis and Walter Alvarez in 1980. Luis was a Nobel Prize winning particle physicist and his son Walter was a professional geologist who discovered a thin band of Iridium-rich rock at the geological boundary between Cretaceous and Tertiary rocks. That was weird because Iridium is heavy, has an affinity for Iron and is rarely found in the Earth's crust. Alvarez and Co [there were other collaborators who tend to get washed out of the story] suggested that the Iridium came from an extraterrestrial source as a massive asteroid collided with the Earth scattering debris from itself and the impact crater far and wide. Being scientists they could estimate the size of the asteroid and the size of the crater and part of the scepticism with which their hypothesis was
In contrast, he little furry creatures, scurrying about between the dinosaur's legs and happy-as-larry in the dark, started to grow and diversify so that in a geological eye-blink all 20ish Orders of mammals were strutting a fretting their hour on the stage: bats, rodents, carnivores, cetartiodactyla, elephants, armadillos and uncletomcobblios. Why is this event important? Because I am, even at this moment, using electricity to whack out another post on The Blob and so cranking up my carbon footprint for 2015. Shoving up the temperature a couple of degrees centigrade doesn't sound like much to us - sounds pretty good in drizzly Ireland - but may knock out a single over-sensitive species in our complex of inter-locking ecosystems. Because it is system, that loss will have unpredictable and cascading effects on the members of the ecosystem who remain.