How is radioactive dating important for providing evidence for evolution?

Radioactive dating can only provide indirect evidence for evolution. Radioactive dating can provide supporting evidence for evolution.

The easiest form of radioactive dating to understand is Carbon 14.
Carbon 14 with a half life of 5,700 years can only be used to date the most recent fossili. 57.000 years equals 10 half lives. A fossil of 57,000 years would have # 1/2^10# = # 1/1024 = .000098 = .0098%
It would require great precision to measure such a small amount of radioactive carbon. Also any erosional loss of material or slight contamination would throw off any values.

Fossils often have no carbon in them at all. Molds, and casts are impressions in the rock containing no carbon. Others like fossilized wood have had the organic material completely replaced by minerals. Mineralization of organic material is very common in fossils. Obviously Carbon 14 can not be used in mineralized fossils.

Other forms of radioactive dating are based on rocce ignee. Since fossils are always found in rocce sedimentarie these forms of radioactive dating can not be used in sedimentary layers. Potassium and Uranium decay can not be used to directly date fossils. The rock layers below or above a sedimentary layer can be approximately dated using radioactive decay. Igneous incursions into sedimentary layers can be dated using Uranium decay.

Uranium has a have life of 4.5 billion years. Again small changes in the amount of Uranium or the amount of Lead can lead to large differences in the estimated age of the igneous layers. Also the calculation are based on assumptions that the layer started with no lead and 100% uranium and no erosion has occurred. These not only unproven assumptions but also very unlikely assumptions.

Radioactive dating then can only be used to generally support the theory of evolution.