Seen many naturally occurring robotics?
By definition, I can't have. Robot's are artificial beings. (While, that really depends on the definition. Other definitions say that it is any system controlled by a virtual agent. Ie a electronical program.*)
But that isn't really the question. After all, all things must have a cause. However, those things that can make themselves happen again, will happen again. At this moment there are viruses out there that no longer look anything like the thing the programmer originally created, because they're equipped with self-modifying code. Evolving programs are already a thing, and while questionably alive (More alive than a real world virus, I would argue) they do show evolution.
We can already create self-upgrading programs, it's merely a matter of developing the technology to let them upgrade their shells as well.
*Something for which we don't qualify, as while our nerve system is electric, we also have significant chemical systems.
On a side note, the brute force approach is very useful in science nowadays. Rather than trying 1000 materials to see which one is the best, you can just have a supercomputer simulate millions of materials, and then test the top 100. Cheaper and more effective.
You can pretty much use that for every field of science.