An acoustical analysis of the grunts, barks, wahoos, copulation calls, and yaks from baboons shows that, like people who use several vowels during speech, these nonhuman primates make five distinct vowel-like sounds, according to a study published January 11, 2017 in the open-access journal PLOS ONE by Louis-Jean Boë, Grenoble Alpes University, France, and colleagues.