How did the earliest organisms on Earth most likely produce ATP?

Question

Quizplus · Accepted Answer

Glycolysis is the most ancient metabolic pathway in living organisms and is believed to have evolved early in the Earth's history. It is the process by which glucose is broken down into pyruvate, releasing energy that can be used to produce ATP. While oxidative phosphorylation and the citric acid cycle are more efficient processes for ATP production, they arose later in evolution.

How Did the Earliest Organisms on Earth Most Likely Produce