Twins: Genetic Effects on Physical Growth from Birth to Four Years

The shapes of the skull of the common people in Tokyo-Yokohama area have un dergone secular changes from the proto- historic age to the present day. The common people in Japan are consid ered to be the descendants of protohistoric farmers who inhabited and cultivated the same locality from generation to generation. Nevertheless, the mentioned changes can be regarded as gradual ones if skeletal ma terials of the intermediate ages (5th to 19th century A.D.) are examined. features, elevation of the other traits, such as the sum of cranial and cranial module, hori zontal circumference, and mediosagittal arc of the cranium, have undergone little change. The results of a twin study are supposed to elucidate the probable reason for these age changes. Anthropological measurements twin circumference, head; medium bizygomatic breadth; length-breadth nasal of the nasal