time_units: generations
defaults:
  epoch:
    start_size: 1000
demes:
  - 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