The number of individuals in deme O remained at 4530 until 3985.682 generations ago, at which time it changed to a new stable size of 4274.
time_units: generations
demes:
  - name: O
    start_time: .inf
    epochs:
      - start_size: 4530
        end_time: 3985.682
      - start_size: 4274
        end_time: 0