Colour blindness and natural selection: studies in four nomadic tribal groups from Andhra Pradesh, India

438 males and 369 females from four endogamous nomadic groups of the Yerukala viz. Suvvi, Badda, Uppu and Kunchapuri of Andhra Pradesh (India) were examined for red-green colour blindness using the 15th edition of Isihara's colour blindness chart. The absence of defective colour vision in the Badda Yerukala and very low frequencies among the other groups agree not only with the hypotheses of Post (1962) and Pickford (1963) concerning the operation of natural selection, but corroborates, too, the opinion of Malhotra (1978) that nomads by virtue of their life-style demand good colour vision.