The number of individuals in deme Z remained at 8851 until 5130.08 generations ago, at which time it changed to a new stable size of 7991.
time_units: generations
demes:
  - name: Z
    start_time: .inf
    epochs:
      - start_size: 8851
        end_time: 5130.08
      - start_size: 7991
        end_time: 0