When and how do scientists think sponges evolved?

Scientists think sponges evolved from protists very early in the Cambrian period. In fact, the flagellated collar cells in sponges bear a striking resemblance to the cells in a group of colonial protists. this similarity has led scientists to hypothesize that sponges evolved from such colonial protists.

They are stuck to the floor in the oceans, sea, and rivers. They are known as Porifera. The Poriferans are simple multi cellular animals. Sponges are very primitive creatures that scientist think evolved around 500 million years ago