Has removal of excess cysteine led to the evolution of pheomelanin?

This is the authors' abstract. We don't add key points for this paper.

Pheomelanogenesis may have evolved as an excretory mechanism to remove excess cysteine, and in humans this might potentially confer a greater ability to avoid disease such as Parkinson's and Alzheimer's disease, in which excess cysteine is a contributory cause.