Mass Extinctions and Evolution

Again, at www.wired.com/wiredscience/2010/09/mass-extinction-dynamics/ this story is a repeat – but worth repeating. A reappraisal of the fossil record, it is thought, reveals that global mass extinction events are not actually short term diversions along life’s uniformitarian course but such events send life careering down wholly new avenues. The speed at which groups adapt and fill open ecological niches is made possible by mass extinction events (or catastrophes) and these actually change the dynamics of evolution. The winners and losers at any given time cannot be predicted from what went before – which is often diametrically different to what follows. Groups that diversifed rapidly flourished but each group has fixed dynamics – evolution is not an endless stream of new life forms. This is why we don’t have trillions of species – and the future is unpredictable. J Alroy, The Shifting Balance of Diversity among major marine animal groups, in ‘Science’ 329 (No 5996) sSept 3rd, 2010.