time_units: generations
demes:
- name: deme2
  start_time: .inf
  epochs:
  - {end_size: 1200.0, end_time: 0, start_size: 1200.0}
- name: deme1
  start_time: 4.0
  epochs:
  - {end_size: 1200.0, end_time: 0, start_size: 1200.0}
  ancestors: [deme2]
migrations:
- {source: deme1, dest: deme2, start_time: 4.0, end_time: 0.0, rate: 0.0025}
- {source: deme2, dest: deme1, start_time: 4.0, end_time: 0.0, rate: 0.0025}