time_units: generations
demes:
  - name: X
    epochs:
      - end_time: 1000
        start_size: 2000
  - name: A
    ancestors: [X]
    epochs:
      - start_size: 2000
  - name: B
    ancestors: [X]
    epochs:
      - start_size: 2000
pulses:
  - sources: [A]
    dest: B
    proportions: [0.05]
    time: 500