First of all, I think you exaggerate the amount of mutation required to alter body plans, particularly when starting from a relatively undifferentiated plan.
Second, evolution is a road with no easy way back. When looking to the future, the only requirement for a mutation is that it not kill the individual before reproduction. there is no preferred direction and no specification or goal. Going backwards is unlikely for the very reason that ID claims evolution is impossible. If you try to evolve backwards (say as a deliberate laboratory experiment in which humans control selection) you run into all the improbabilities that are bandied about in the phrase, specified complexity. You would need specific mutations to occur in a specified sequence.
If you want to understand what evolution is, you must abandon the practice of starting with what has happened in history and trying to calculate the odds of reaching this destination. This was never the destination. There never was a destination. What happened, happened. The only necessity for evolution to occur is that enough individuals reproduce to avoid extinction. There is no necessity to evolve in any particular direction.
So what is my point? It is simply that when you start from something relatively simple, there are many directions towards greater complexity. Start with a sphere and everything is a non-sphere. Start with a cylinder and every lump is an appendage. But onde you have appendages, you no longer have the option of starting from a sphere or cylinder. Once a branch has begun it is not going to unbranch. Large scale body plans become more differentiated and more specialized, but they cannot return to the simple form that would allow a radically new body plan.
Do you mean to explain the Cambrian explosion as reducible to mutating body plans? It looks to me that there were no "body plans" prior to the Cambrian explosion -- at least not of any of the higher phyla. Then, suddenly -- bang! -- there were body plans. How long would it take a process of mutation to get from a "relatively undifferentiated body plan" to the body plans of all the great phyla -- which all erupted in a single relatively short time-frame, and all over the world? And after which, no new phyla have emerged? Did the process of mutation stop after the CE?
These are real questions, js1138, not figments of someone's imagination.
I have a bump on my neck. I'm evolving into a bumpy mutant!
What would be the “undifferentiated body plan?”
Second, evolution is a road with no easy way back. When looking to the future, the only requirement for a mutation is that it not kill the individual before reproduction. There is no preferred direction and no specification or goal.
So a mutation effectively is a purposeless event? It’s just something that happens, and assures improved reproduction prospects provided it doesn’t kill the organism undergoing mutation in the first place? And mutation seems rather indifferent even to reproduction prospects, for that’s just a matter of chance also (i.e., surviving the mutation). So mutation is indifferent, has no preferred direction as in, e.g., a "life direction?"
Going backwards is unlikely for the very reason that ID claims evolution is impossible.
I wasn’t aware that “ID claims evolution is impossible.” I thought ID’s claim is that Darwin gives only a partial account of it.
If you try to evolve backwards (say as a deliberate laboratory experiment in which humans control selection) you run into all the improbabilities that are bandied about in the phrase, specified complexity. You would need specific mutations to occur in a specified sequence.
I think you need a bit more than “specified sequence” or a particular progression in time. For when a mutation “hits,” it will affect one part of the organism and change it in such a way that many different other functionalities within the organism would have to change to accommodate it. It seems mutation pertains to the modification of one particular organic functional space. Does the mutation itself contain the information that the other bodily functions would need in order to achieve their own appropriate modifications in response to it? It seems that if all the other relevant functions cannot do that, then the mutation would lead to death, not to improved survival fitness or enhanced reproductive prospects. So, what is the information source that enables such synergized global cooperation and integration in response to the mutated “part?”
If you want to understand what evolution is, you must abandon the practice of starting with what has happened in history and trying to calculate the odds of reaching this destination. This was never the destination. There never was a destination.
Can you give me any evidence that “there never was a destination?” What is the point of an evolutionary process that is not evolving from something, toward something? Isn’t this the very meaning of the word “evolution?” You yourself suggest evolution is ultimately about reproductive success. But what would be the meaning of “success” if there is no purpose that nature seeks to fulfill by which we might judge whether a process is successful or not?
What happened, happened. The only necessity for evolution to occur is that enough individuals reproduce to avoid extinction. There is no necessity to evolve in any particular direction.
The past is an accident, and the future is an accident looking for a place to happen. If this isn’t a philosophic statement then I don’t know what it is. Again, can you test and falsify this hypothesis? Can you make any prediction from it? If not, then it isn’t science.
So what is my point? It is simply that when you start from something relatively simple, there are many directions towards greater complexity. Start with a sphere and everything is a non-sphere. Start with a cylinder and every lump is an appendage. But once you have appendages, you no longer have the option of starting from a sphere or cylinder. Once a branch has begun it is not going to unbranch. Large scale body plans become more differentiated and more specialized, but they cannot return to the simple form that would allow a radically new body plan.
I get this, js1138: Evolution as irreversible process. I wholly agree with the insight. But we need more than “cylinders with lump appendices.” For as noted above, when the new “lump” appears, this is not an event taking place in isolation. All other parts of the organism are affected and must undergo suitable modifications to accommodate the new lump in order for it to take hold and not kill the cylinder. So to speak.
With the Cambrian explosion, it isn’t all that clear really what the process was starting from. The scanty prior fossil record isn’t particularly eloquent on this point. And with the CE, there was an explosion of new phyla globally in a relatively compressed time period. PatrickHenry says that 50 million years is not a short time period. But from the standpoint of the evolution of the Universe, it is a drop in the bucket.
Well js1138, hope I have understood what you wrote. I probably haven't explained this very well; but I did try. Thank you for writing!