The "creator" would be random chance. So I'd say the creation is a bit better.
If you speak of a creation on the genetic level (a mutation), than you could say whatever the cause of a mutation should be (often radiation) could be the creator. But evolution is based on the principle of natural selection, that individuals with favorable genetic traits will tend survive, so in that sense you can say nature creates new species. By nature, of course, I mean one or more specific agent(s) of selection, which could be anything from a predatory species to an entire eviornment or ecosystem.
Radiation caused genetic mutations billions of years ago? Weird.
Mutations are random switches or duplications or deletions of nucleotides in a DNA sequence. These mutations cause mistakes in the amino acid chains that the DNA sequence codes for proteins, which causes the synthesis of different proteins. The proteins give an organism its characteristics, if a protein is changed and the change it causes is desirable, that organism will survive to reproduce. It goes on from there, don't feel like explaining anymore.
Absolutely, for instance, strong radiation such as UV or simmilar can cause a thiamine-thiamine dimer to form (between two adjacent thiamine base pairs), making a section of genetic code unreadable, or a DNA Polymerase may excise that section of code from the genome. Radiation causes a multitude of different DNA damages. Addition of DNA could be cause by things other than rad though, for instance a lysogenic virus can be the vector of mutation, or coud be a mistake in the transcription process (usually a missense mutation, rarely nonsense), then come large scale chromosomal abberations such as fusions or deletions of whole parts.
Certain chemicals cause rearrangement in genetic codes, even high temperature can damage DNA. But radiation does happen to be a leading cause of DNA damage (UV). In fact, the body has polymerases that regularly repair or replace code damaged by radiation. Some people who cannot be in the presense of UV light lack a functioning version of this enzyme.
I am a biochem student so I should know a little about some of this stuff...
Edit: IN case anyone is interested, the name of this condition is xeroderma pigmentosum, and these people are very succeptable to skin cancer if they don't wear protective clothing outside (Because of their lack of the functioning excision/repair enzyme).