The number of individuals in deme U remained at 768 until 7702.635 generations ago, at which time it changed to a new stable size of 2476.
time_units: generations
demes:
  - name: U
    start_time: .inf
    epochs:
      - start_size: 768
        end_time: 7702.635
      - start_size: 2476
        end_time: 0