Y deme's population was steady at 1739 before it increased to 8711 5447.3 generations ago, maintaining that number to the present.
time_units: generations
demes:
  - name: Y
    start_time: .inf
    epochs:
      - start_size: 1739
        end_time: 5447.3
      - start_size: 8711
        end_time: 0