Up until 1837.591 generations ago, the count of Z deme was 6874. Following that period, it changed to 8313, where it has persisted until now.
time_units: generations
demes:
  - name: Z
    start_time: .inf
    epochs:
      - start_size: 6874
        end_time: 1837.591
      - start_size: 8313
        end_time: 0