Comment by storus

Melanin is used as a solar panel, capturing gamma rays and then passing the resulting consistent flow of excited electrons over to the Krebs cycle with the help of CO2; like in photosynthesis. Humans run on electrons resulting from Krebs cycle as well, just the input is different. By using it as shielding, you'd simply decrease the amount of ionizing radiation hitting humans inside the spaceship. In other words, it would be better than some static material as it consumes part of incoming radiation for its own existence.