Which type of organism most likely evolved first?

Answer: Prokaryotes.

Explanation:

Prokaryotes are the type of the organism that evolved first. They have the simplest body organization and the lacked main cell organelle that is responsible for the replication.

The prokaryotes means primitive and they lacked nucleus and many other cell organelles that complex structures have.

They are single celled organism adaptive of living in earth older environment.

it is simple prokaryotes