Until a shift occurred 4180.235 generations ago, deme Z's population was consistently 262. Since then, it increased to 4861, a number that has remained unchanged to the current time.
time_units: generations
demes:
  - name: Z
    start_time: .inf
    epochs:
      - start_size: 262
        end_time: 4180.235
      - start_size: 4861
        end_time: 0