Until a shift occurred 1041.19 generations ago, deme D's population was consistently 604. Since then, it grew to 2045, a number that has remained unchanged to the current time.
time_units: generations
demes:
  - name: D
    start_time: .inf
    epochs:
      - start_size: 604
        end_time: 1041.19
      - start_size: 2045
        end_time: 0