Deme S maintained a population of 9396 until there was a shift 9826.0 generations ago that decreased its numbers to 644, a figure that has remained the same since.
time_units: generations
demes:
  - name: S
    start_time: .inf
    epochs:
      - start_size: 9396
        end_time: 9826.0
      - start_size: 644
        end_time: 0