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.
when did the first fish appear on earth
The evolution of fish began about 530 million years ago during the Cambrian explosion.
when did the first reptile appear on earth
The origin of the reptiles lies about 320–310 million years ago, in the swamps of the late Carboniferous period, when the first reptiles evolved from advanced reptiliomorph labyrinthodonts.

Question: what was the first creature
Self-contained rewrite: what was the first creature to appear on earth