Radiation itself hasn't "evolved" in the way we understand evolution to occur in living organisms. Radiation has always existed, as it's a fundamental part of the universe.

Here's what we can say about radiation on Earth:

* Early Earth: Earth was bombarded with radiation from the sun and other cosmic sources. This radiation was much more intense than it is today.

* Radioactive Elements: Radioactive elements like uranium and thorium were present in the early Earth, contributing to the overall radiation environment.

* Life's Evolution: Early life forms evolved in this high-radiation environment, developing mechanisms to cope with it. Some organisms even utilize radiation in their processes, like certain bacteria.

So, while we can't pinpoint a specific date for the "evolution" of radiation, it's safe to say that radiation has been a constant presence on Earth since its very beginning, and life has adapted and evolved alongside it.