Originally, deme S had a population size of 9076, which changed to 5009 around 268.8 generations ago and has not changed since.
time_units: generations
demes:
  - name: S
    start_time: .inf
    epochs:
      - start_size: 9076
        end_time: 268.8
      - start_size: 5009
        end_time: 0