The population of deme O held at 8331 until 6429.0 generations back, when it changed reaching 7839, which has been constant since then.
time_units: generations
demes:
  - name: O
    start_time: .inf
    epochs:
      - start_size: 8331
        end_time: 6429.0
      - start_size: 7839
        end_time: 0