The number of individuals in deme U remained at 2740 until 3545.5 generations ago, at which time it changed to a new stable size of 7476.
time_units: generations
demes:
  - name: U
    start_time: .inf
    epochs:
      - start_size: 2740
        end_time: 3545.5
      - start_size: 7476
        end_time: 0