Conversation so far:
when did the first primates appear on earth
Genetic studies show that primates diverged from other mammals about 85 million years ago, in the Late Cretaceous period.
when did the first birds appear on earth
Fossil records suggest that modern birds originated 60 million years ago, after the end of the Cretaceous period about 65 million years ago when dinosaurs died off.

Question: when did the first fish
Self-contained rewrite: when did the first fish appear on earth