A Genetic Study of the Vibrato

The question of whether or not the vibrato, which is found in the singing voice of all vocal artists and of some untrained adults, and occasionally in the speaking voice, is learned, or is due to some inborn physiological characteristic is one which has been the subject of considerable speculation. Upon this question rest the answers to such questions as these: Will there come a day when voices with vibrato will not be considered beautiful? Should the vibrato be expected to appear automatically when a student of singing learns to vocalize properly or is there a special technique to be acquired