Originally, deme Z had a population size of 1947, which decreased to 836 around 1736.0 generations ago and has not changed since.
time_units: generations
demes:
  - name: Z
    start_time: .inf
    epochs:
      - start_size: 1947
        end_time: 1736.0
      - start_size: 836
        end_time: 0