BBFBLBRBSBTBVBXCSDDADCDDDGDKDSDTEFGHBHDHFHGJKJXKFLBMLNNonePAPCPEPNPQPRPSPTPZQAQCQEQHQLRCSBSFTXZ1850185518601865187018751880188518901895190019051910191519200.10.20.30.40.50.60.70.80.9123456789102030405060708090100Usage of natural selectionper Million Words02000000004000000006000000008000000001000000000Total words in corpus