W deme's population was steady at 2191 before it changed to 4555 3599.0 generations ago, maintaining that number to the present.
time_units: generations
demes:
  - name: W
    start_time: .inf
    epochs:
      - start_size: 2191
        end_time: 3599.0
      - start_size: 4555
        end_time: 0