"Children of mixed spirits", as the Cro-Magnons call them, are mis-matched combinations of both Cro-Magnon and Neanderthal phenotypes physiologically as they are genetic hybrids, with some traits (like facial features) appearing blurred or distorted when compared side-by-side. Of the five mixed-race people depicted in the series, only one has had the restricted vocal range of the Clan (Rydag, from "The Mammoth Hunters"), and all but one has been seen using Clan sign language, the sole exception being the difficult and disconsolate self-loathing Brukeval (who is in clear psychological denial about his ancestry), in "The Shelters of Stone".The vocal range of one of the mixed-race persons is as of yet unknown because she was only a baby when we meet her in "The Clan of the Cave Bear".