INTERNATIONAL JOURNALOF ANTHROPOLOGY Vol. 7 - N. 2 (41-51)- 1992 G. Livshits Research Unit - Human Population Biology, Division of Anatomy and Anthropology Z. Cohen I. Otremski Department of Traumatology and Orthopedics, Ichilov Municipal Hospital, Sackler Faculty of Medicine Tel Aviv University Ramat Aviv 69987, Tel Aviv Israel Key words: motor traits, siblingresem- blance. Interrelations between early child develop- ment, gestational age and birth weight Five traits of early child development were studied in 656 infants from the day of birth till 2 years of age. The infants selected for follow-up were born at 26-42 weeks of gestational age and with a birth weight accordingly ranging from 860 to 4560g. Analysis of variance was carried out for each of the following five traits which entailed the age at which a child: 1) turned himself over (turned); 2) sat unsupported for a few seconds (sat); 3) stood up (stood); 4) walked unsupported (walked); and 5) cut its first tooth (tooth). The results of this survey show no significant sex differences in the age of initial occurrence of any of the studied traits. Comparison with older siblings of the surveyed infants indicated a significant sibling resemblance component for all 5 traits, with the respective intraclass correlation coefficients ranging between 0.34 and 0.53. Gestational age and birth weight, but not "tooth", appeared to be important messages of an infant's motor development, insofar as onset of the studied traits. The separate correlations of "turned", "sat", "stood" and "walked" with gestational age or weight were all negative and statistically highly significant. Introduction Studies of human growth and development during infancy and childhood have been pivotal to the development of human biology as a scientific discipline. Although the literature on human growth is extensive and diverse (vide Falkner and Tanner, 1986), quantitative studies of motor development in early childhood are still very limited. It is obvious however, that motor abilities must be analysed for adequate therapy. Early detection of abnormality may be made by the physiotherapist, who is well familiar with the normal patterns of child development. Therapy in such cases could prove partly beneficial to motor development apart from providing an index of the child's progress (Levitt, 1986, Ch. 2), and thus for example, may be able to identify spinal muscular atrophies associated with various motor disorders, such as inability of the child to stand or sit, etc. (Hyde, 1986). Yet, despite the fact that traits of early child development are widely relied upon in child health clinics and are deemed highly important for predicting future growth and development (Illingworth, 1987; 1988), only very few studies have been undertaken to determine the period for motor learning in recent years (Scott, 1986; Livshits, 1988). It thus becomes imperative to establish adequate standards for the various characters of early child development, especially since recent generations of neonates have been characterized by a considerable proportion (upto 18%) of low birth weight as well as preterm deliveries (Glasgow and Overall, 1983; Kramer, 1987). One of the most likely reasons for the paucity of publications in this field is that such studies