The population of deme R held at 3703 until 4738.7463 generations back, when it changed reaching 9774, which has been constant since then.
time_units: generations
demes:
  - name: R
    start_time: .inf
    epochs:
      - start_size: 3703
        end_time: 4738.7463
      - start_size: 9774
        end_time: 0