While Miller's landmark 1953 experiment showed how life's building blocks _may_ have formed on the early Earth, Millers experiment is not a test of, or support for, evolutionary biology. Evolution starts after the origin of life. This origin itself is a question for chemistry, geochemistry and biochemistry. The nature of the atmosphere at the time of the origin of life is still poorly understood. An atmosphere of the type Miller originally used still can't be completely excluded. However, Miller-Urey syntheses work in several other plausible atmospheres, including the best available model we have to date. Furthermore Miller-Urey mechanisms are not the only source of source of lifes building blocks for the early Earth. The origin of life is still not understood, despite significant progress over the past few decades. However, this does not affect the validity of evolutionary biology.

See also:

Ian Musgrave