The population of deme Y held at 3206 until 824.9 generations back, when it increased reaching 8137, which has been constant since then.
time_units: generations
demes:
  - name: Y
    start_time: .inf
    epochs:
      - start_size: 3206
        end_time: 824.9
      - start_size: 8137
        end_time: 0