time_units: generations
defaults:
  epoch: {start_size: 1}
demes:
- {name: A}
- {name: B}
- {name: C}
migrations:
- {rate: 0.6, source: C, dest: A, start_time: 100, end_time: 50}
- {rate: 0.6, source: B, dest: A, start_time: 200, end_time: 100}