Originally, deme O had a population size of 4473, which changed to 497 around 8133.2 generations ago and has not changed since.
time_units: generations
demes:
  - name: O
    start_time: .inf
    epochs:
      - start_size: 4473
        end_time: 8133.2
      - start_size: 497
        end_time: 0