Stimulated by the nth discussion with Zachriel on this point, I would like to offer here some thoughts about the difference between Natural Selection and Artificial Selection.
First of all, the dramatic limitation of NS is the following: it works on one functional specification, and one functional specification only: reproductive advantage.
In a sense, that specification is the byproduct of the system: biological beings that reproduce, that use limited resources to do that, and that compete for those resources. So, NS is a selection made possible by the existence of a complex functional system, and it selects for improvement in a function critically predefined in that system: reproductive success. So, it is a byproduct of the functional complexity already existing in the system.
Now, the functional specification: “reproductive success” is rather generic. It can certainly include many sub-functions. That’s the point that neo-darwinists stress. They say: OK, NS can select only for reproductive success, but reproductive success can include any function, and everything which goes in that sense can be selected.
Well, this is a false reasoning, which takes into no account the nature of complex information. The simple fact is: the search engine to which NS can be applied is random variation, and only random variation (I exclude for the moment possible algorithmic adaptation mechanisms). So, NS works on variation that is random, and not purposeful. Can that mechanism build complex functional information?
The simple answer is: no. Simple functional variation can certainly be generated by random variation, and therefore selected by NS. Why? because a few bits of variation are in a search space small enough to be explored, even many times, by biological RV. Those rare instances where the variation can give an advantage, with a bit of luck, can certainly be selected. That is the case of simple forms of antibiotic resistance. We can call those cases “molecular microevolution”. The few examples we have of that are the only empirical examples of NS at work in biology.
But what about some function which can give reproductive advantage, but which appears only if at least, say, 500 bits of specific information are found?
Such a result is definitely beyond any resource of RV. Therefore, it will never be achieved, and therefore never be selected.
Neo-darwinists, like Zachriel, argue that gradual pathways exist that will build those 500 bits of specific information in small steps. That is simply a fairy tale, existing only in their imagination. Information does not work that way. If I need 100 specific aminoacids to make something work (a case very common), then there is obviously no pathway which goes to that sequence step by step. Why? Because those 100 AAs are specific to the function. Fragments of the sequence have no special meaning and function, unless the complete sequence is achieved.
What about AS? Let’s take the case of the ATP binding protein, quoted by Zachriel (IOWs the Szostak paper).
This is AS, as many times argued by me here. The designer starts by conceiving and defining a function: “I want a protein which can effectively bind ATP”. That is the functional specification, and it is a form conceived in the consciousness of the designer.
As anyone can see, the function is very different from the single function available to NS: reproductive success.
Then, the designer uses his cognitive understanding of protein biochemistry and lab techniques to devise a strategy to implement his goal.
First of all, he sets a system that measures and extracts those molecules which bind ATP.
This point is very important, and it shows one of the main reasons why AS is so effective, while NS is not.
AS can measure the function defined by the designer at any desired level of sensitivity. Instead, NS has a definite threshold, under which no selection happens: reproductive success must be present, and enough of it to ensure the fixation of the trait.
That means that our designer, if interested in ATP binding, can select molecules which bind ATP with any level of affinity. There may be practical limitations due to the technology used, bu in principle any level of binding can be detected.
The reason is simple:
1) In NS, the coupling between the new function and the selection is direct: it is due to the reproductive success conferred by the function itself.
2) In AS, the coupling between the new function and the selection is indirect and symbolic: it’s the designer of the procedure who connects two events completely unrelated, for example ATP binding and the selection and expansion process. (UB, are you there? 🙂 )
In our example of ATP binding, then the designer chooses to use some form of artificial RV (in that case, mutagenic PCR), and to apply it in rounds coupled to artificial selection again and again.
The results are powerful: he obtains, in a short time, a protein with strong affinity for ATP.
The important point is: while that protein satisfies well enough the functional definition for which it was artificially selected (ATP binding), in no way it confers a reproductive advantage. So, even at the end of the artificial selection procedure, still the protein is not in the range of NS.
So, to sum up, the main differences between NS and AS are:
1) AS can define any function, and select for it. NS works only on one function: reproductive success.
2) In NS, the coupling between function and selection is direct: it’s the function itself which confers the reproductive advantage, which is the reason for the selection itself. In AS, the coupling between the defined function and the selection process is indirect and symbolic: the connection is established by the designer, by definite procedures designed by him.
3) NS has a definite threshold of measurement: it can only act if enough reproductive success is present as to ensure the fixation of the trait. AS can measure and select any desired level of the defined function.
4) In NS, the only selecting procedure is tied to the reproductive success, and is in essence differential reproduction. In AS, any intelligent procedure can be used to isolate, expand and fix the desired function.