Up until 6078.0 generations ago, the count of B deme was 2146. Following that period, it increased to 4990, where it has persisted until now.
time_units: generations
demes:
  - name: B
    start_time: .inf
    epochs:
      - start_size: 2146
        end_time: 6078.0
      - start_size: 4990
        end_time: 0