For the J deme, the population size remained at 5500 until 6900.0 generations ago, at which point a linear change took place until 2924.7 generations for size 5403. Afterward, the population saw an linear reduction to 2615 by 1984.139. From 1984.139 generations ago to today, there's been a linear growth from 2615 to 4478.
time_units: generations
demes:
  - name: J
    start_time: .inf
    epochs:
      - start_size: 5500
        end_time: 6900.0
      - start_size: 5500
        end_size: 5403
        end_time: 2924.7
        size_function: linear
      - start_size: 5403
        end_time: 1984.139
        end_size: 2615
        size_function: linear
      - end_time: 0
        start_size: 2615
        end_size: 4478
        size_function: linear