time_units: generations
defaults:
  deme:
    proportions: [0.1, 0.9]
demes:
- name: a
  proportions: []
  epochs:
  - {start_size: 1}
- name: b
  proportions: []
  epochs:
  - {start_size: 1}
- name: c
  ancestors: [a, b]
  start_time: 100
  epochs:
  - {start_size: 1}