It's also good to remember that while genetic mutations may be random, the resulting phenotypes are not. The catch with the watch/monkeys anology is that, intuitively, a watch's mechanism is fragile to change: the watch will break with almost _any_ random change that comes up. If a genetic change produces a new limb in an organism, the limb will be covered in skin, enervated, vascularized, and sometimes partially muscled and connected to the rest of the skeletal system. The extra limb would not be perfect but it's not a random lump of tissue. That phenotype is something selection could act on.
In other words, if we want to explain evolution by trying to describe how random change might produce (or improve) a watch, we've already given up half the argument. Kirschner and Gerhart in 'The Plausability of Life' present the underlying concepts very nicely. Best, Krzysztof ----------------------------------------------- Krzysztof Sakrejda-Leavitt Organismic and Evolutionary Biology University of Massachusetts, Amherst 319 Morrill Science Center South 611 N. Pleasant Street Amherst, MA 01003 work #: 413-325-6555 email: [email protected] ----------------------------------------------- On Sun, Feb 15, 2009 at 2:24 AM, Barney Luttbeg <[email protected]> wrote: > Michael Harvey wrote: >> >> When I studied genetics I learned that natural mutations were largely >> random. The creationists' scorn of improving a watch by a random change is >> strong. I would like to see studies showing how environmental parameters can >> direct chromosomal changes so that they are not random and that adaptation >> will occur and makes sense. Without such demonstration, we are all asked to >> "believe" evolution. >> >> I don't work in this field and may have missed such reports but I have not >> seen them. >> > The mutations are largely randomly but selection is not. In other words the > building blocks with which evolution occurs is randomly formed, but natural > selection does not randomly select which blocks are used. > > Barney Luttbeg > --
