The Mushmen/MushWomen have lived on the mushroom Islands for a long time, they lived there before the dinosaurus!
they mostly eat mushroom stew.

They have found out that the mycelium that the grass was made of, has a lot of good minerals for their skin.
after discovering this, they mixed the mycelium and milk, to make a kind of cream that they smeared all over their bodies.
after centuries of evolution their cream simply became a part of their skin.

The Mushmen have also discovered that the mushrooms growing on the island is very hard on the outside, but soft and warm on the inside.
This led them to using the mushrooms as gloves, hats and shoes.

Entry for Biome Dependent Event.