time_units: generations
demes:
- name: deme1
  start_time: .inf
  epochs:
  - {end_size: 100, end_time: 0, start_size: 100}
- name: deme2
  start_time: .inf
  epochs:
  - {end_size: 100, end_time: 0, start_size: 100}
migrations:
- {source: deme1, dest: deme2, start_time: .inf, end_time: 4000.0, rate: 0.00025}