Eric Drexler has written a paper entitled Biological and Nanomechanical Systems: Contrasts in Evolutionary Capacity that explores the differences between biological organisms and artificial machines, specifically why some products of intelligent design (i.e. design by humans) could never be created by natural selection. Drexler has written a short preface summarising his argument here:
The basic argument is as follows:
- Evolvable systems must be able, with some regularity, to tolerate (and occasionally benefit from) significant, incremental uncoordinated structural changes.This is a stringent contraint because, in an evolutionary context, “tolerate” means that they must function — and remain competitive — after each such change.
- Biological systems must satify this condition, and how they do so has pervasive and sometimes surprising consequences for how they are organized and how they develop.
- Designed systems need not (and generally do not) satify this condition, and this permits them to change more freely (evolving in a non-biological sense), through design. In a design process, structural changes can be widespread and coordinated, and intermediate designs can be fertile as concepts, even if they do not work well as physical systems.
As I read it (and I could be wrong) the basic notion underlying Drexler’s argument is that the kind of mechanical precision demanded by human engineers is not present in the products of natural evolution. Artificial technologies are not yet fungible. If you remove any part of your CPU it will not work. If you remove some parts of someone’s brain then it still works. If you make a small alteration to an organism’s genome it may still work.
In order for evolution to work the replicator needs to function even when it has some small mutation. Artificial technologies generally don’t work when there is some small error in the manufacturing process.