There are about 4000 species in the family Drosophilidae, or 'small fruit flies' -
Drosophilidae - Wikipedia . These species are all descended from a common ancestor. However, since none of them have changed into anything but 'small fruit flies', this diversity of species is not evolution.
There are about 6400 species of mammals -
Mammal - Wikipedia. These species have all descended from a common ancestor. I grant you that, to our eyes, a dolphin, a pipistrelle, a zebra and a lemur are less alike than any four species of fruit flies. However, since none of them have changed into anything but mammals, this diversity of species is not evolution.
Yes, humans and all other mammals evolved from fish. However, fish and humans are both vertebrates. Vertebrates have not changed into anything but vertebrates, any more than fruit flies have changed into anything other than fruit flies.