[Frumious Bandersnatch]

I quite understood what you are saying.  I disagree with your thesis, because things which happened before are not available for use if random chance is the deciding factor.  That's because each chance development, by itself, means nothing without the others to create an organism.  For example, the odds of each individual part of a cell being created by chance are astronomically high, but for all the parts of the cell being created simultaneously and in the right order by chance are absolutely mind-boggling.

Even after an organism is established, what has been created before is not necessarily available, because without any context, it is useless.  Which is why, perhaps, DNA contains so much junk.

[js1138]

Even after an organism is established, what has been created before is not necessarily available, because without any context, it is useless. Which is why, perhaps, DNA contains so much junk.

"Junk" is simply stuff currently in disuse. In a changed context it is available for repair and re-use.