Until a shift occurred 7200.1664 generations ago, deme S's population was consistently 3709. Since then, it decreased to 939, a number that has remained unchanged to the current time.
time_units: generations
demes:
  - name: S
    start_time: .inf
    epochs:
      - start_size: 3709
        end_time: 7200.1664
      - start_size: 939
        end_time: 0