I am quite intrigued by the news stories based on a paper that just came out in Nature on the early history of oxygen producing bacteria (e.g., see the Canada.Com story Thank oxygen-producing bacteria for your existence
and the National Geographic Story Nickel "Famine" Led to Oxygen-Breathing Life?). In short, the paper suggests that about 2.5 billion years ago, the amount of nickel in oceans (and presumably elsewhere) began to decrease, possibly due to changes in volcanism. Furthermore they suggest the reduction in nickel harmed methanogenic microbes which require nickel for multiple processes. Thus the term "nickel famine." As the methanogens declined, many changes occurred including an increase in the oxygen concentration in the atmosphere (with the oxygen coming from cyanobacteria). And presto, the world became just so much more hospitable for many of us and our relatives. Anyway, the term "nickel famine" really stuck with me, so I am making it my evolution phrase of the week.