Until 6123.0 generations ago, the population of deme B was 2913. At that point, it grew to 5292, where it has stayed up to now.
time_units: generations
demes:
  - name: B
    start_time: .inf
    epochs:
      - start_size: 2913
        end_time: 6123.0
      - start_size: 5292
        end_time: 0