For deme Y, the population count was 1311 until a change 5647.0 generations ago, where it increased to 3259, remaining steady thereafter.
time_units: generations
demes:
  - name: Y
    start_time: .inf
    epochs:
      - start_size: 1311
        end_time: 5647.0
      - start_size: 3259
        end_time: 0