Deme Z had an initial size of 543 until 6157.4769 generations ago. At that time, its population size changed to 8906, and has remained there till current time.
time_units: generations
demes:
  - name: Z
    start_time: .inf
    epochs:
      - start_size: 543
        end_time: 6157.4769
      - start_size: 8906
        end_time: 0