Deme J maintained a population of 8739 until there was a shift 2704.26 generations ago that decreased its numbers to 6440, a figure that has remained the same since.
time_units: generations
demes:
  - name: J
    start_time: .inf
    epochs:
      - start_size: 8739
        end_time: 2704.26
      - start_size: 6440
        end_time: 0