time_units: generations
defaults:
  deme: {start_time: 1000, ancestors: [X]}
  epoch: {start_size: 1000}
demes:
  - name: X
    start_time: .inf
    ancestors: []
    epochs:
      - end_time: 1000
  - name: alpha
  - name: beta
  - name: gamma
  - name: delta
    epochs:
      - end_time: 500
      - start_size: 200
        end_time: 0
migrations:
  - demes: [alpha, beta, gamma, delta]
    rate: 1e-4