Z deme's population was steady at 2011 before it changed to 5665 4952.0 generations ago, maintaining that number to the present.
time_units: generations
demes:
  - name: Z
    start_time: .inf
    epochs:
      - start_size: 2011
        end_time: 4952.0
      - start_size: 5665
        end_time: 0