Originally, deme B had a population size of 6439, which changed to 1114 around 6760.0 generations ago and has not changed since.
time_units: generations
demes:
  - name: B
    start_time: .inf
    epochs:
      - start_size: 6439
        end_time: 6760.0
      - start_size: 1114
        end_time: 0