The emergence of complexity

Carl Zimmer has a nice piece on the development of limbs in the Science section of today's New York Times. He has the space to go into much more detail than Lewis Wolpert was able to on The Forum the other day, and what he describes illustrates the basic principles we've discussed, if not in so many words. He talks about the essential role of the signaling that goes on between cells to tell them what to do next, of contingency, the fact that what a cell does next depends on what it has just done, of cooperation at many levels, of modularity and chance. A pretty simple description of how complexity arises.