Up until 8181.9036 generations ago, the count of R deme was 6580. Following that period, it changed to 3856, where it has persisted until now.
time_units: generations
demes:
  - name: R
    start_time: .inf
    epochs:
      - start_size: 6580
        end_time: 8181.9036
      - start_size: 3856
        end_time: 0