Hi KBC, how are you liking the boards?
My point was that with an infinite set of possible forms it would be impossible for random mutation to code for a selectable mechanically functional form.
When a sauropod produces offspring they don't have a random genome attached to them, and evolutionists don't state that this is needed for evolution to work. The offspring inherits the parent's genome. This often comes with small variations. Some of the organisms variation comes from a non-hereditable influence (such as available diet), but some variation can come from these minor variations in the genome.
Some coding DNA did not copy correctly and this results in a
slight variation in the phenotype (for example shorter legs). It might turn out that given the environment the young 'en finds themselves in that shorter legs are a good thing. They increase his chances of passing on the 'shorter legs' gene to his little 'ens. If the variation isn't slight, the chances increase dramatically that they will jump of their island (see below) and bigger the variance the bigger the chance that the poor new organism will be drowning.
Since shape can be anything how does random mutation find the specific limited functional form combinations in a sea of infinite possibilities?
One of the wonderful things we have found with genetics is that the sea might be vast, but there are islands in the gene-sea that represent functional forms. Navigating around the island is like examining all the possible functional forms of a given species. Imagine for example every form of something that can be called a brachiosaur, in the gene-sea they will be very close to each other (Where distance is measured in number of single mutations it would take to get from one form to another).
An amazing discovery in genetics is that many of the 'islands' that currently live on earth are connected by thin bridges (in some cases via other living islands). The bridges themselves are interspersed with small islands.
The theory of evolution, combined with other sciences connected with natural history has shown that in the cases where currently 'living islands' cannot be connected via other living islands they
can be connected via now extinct islands.
For example the human island has a thin bridge with several quite large islands along it leading back to a certain now extinct primate island. That same island has a bridge that leads to chimpanzee island.
We have learned that we can mutate certain proteins, quite massively yet still have them perfectly functional. A yeast's cytochrome c can be entirely replaced with the comparitively mutated human cytochrome c and it will continue yeasting about happily.
Evolution is the process whereby populations change, sometimes members of a population will be pushed down a bridge across the treacherous gene-sea by the force that is selection. If an organism is born so that it has effectively fallen off the bridge, it doesn't reproduce. Therefore only organisms that are fortunate to be born 'on the bridge' survive long enough to create more organisms. Once again only those that are born on a bridge manage to create more organisms.
If the selection pressure continues, and the bridge does not lead to a dead end, the population 'parting the gene-sea' or travelling on an exodus might find itself at another island. Its size then tends to increase to encompass many of the functional forms that the island allows. And there they stay - until another subset is pushed once again into the fray.
Incidentally this has the unusual effect that generally it is only islands are large enough to stand a chance of leaving evidence of their existence. This has come to be known as Punctuated Equilibrium, but it is the same way that Darwin had originally seen.