The number of individuals in deme Z remained at 3384 until 3469.461 generations ago, at which time it changed to a new stable size of 4054.
time_units: generations
demes:
  - name: Z
    start_time: .inf
    epochs:
      - start_size: 3384
        end_time: 3469.461
      - start_size: 4054
        end_time: 0