time_units: generations
defaults:
  epoch: {start_size: 1}
demes:
- {name: a}
- {name: b}
- {name: c}
pulses:
- {sources: [b], dest: a, proportions: [0.6], time: 100}
- {sources: [c], dest: a, proportions: [0.6], time: 100}