J deme's population was steady at 6073 before it changed to 2896 4950.5217 generations ago, maintaining that number to the present.
time_units: generations
demes:
  - name: J
    start_time: .inf
    epochs:
      - start_size: 6073
        end_time: 4950.5217
      - start_size: 2896
        end_time: 0