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The growth in height of 1,202 Quechua and Mestizo children aged 6 to 19 years of the province of Lamas in the Peruvian Eastern Lowlands was studied. As shown by evaluations of ABO, Rh systems, and skin reflectance measurements, the Quechuas are genetically different from the Mestizos. The heights of Quechuas and Mestizos were matched for nutritional status based on measurements of subcutaneous fat and body muscle. The study indicates that: (1) during childhood, Quechuas and Mestizos matched for the same nutritional status attain similar heights; (2) during adolescence (or after the age of 11 years), the Mestizos are significantly taller than the Quechuas of the same nutritional status; 3) during childhood, the relative difference in height between Quechuas and Mestizos matched for the same nutritional status is less than the difference between Quechuas (or Mestizos) of the same genetic composition characterized by good and poor nutritional status. These findings suggest that the influence of environmental factors, such as nutrition, have a greater influence in producing differences in body size during childhood than during adolescence. Conversely, the present findings support the hypothesis that the influence of genetic factors on body size are greater during adolescence than during childhood. However, comparison of adolescent samples of similar genetic composition (whether they be Quechuas or Mestizos), characterized by good and poor nutritional status, reveal large differences in height, suggesting that under conditions of malnutrition, the genetic control of growth is diminished.

Male advancement in the developing hand was evidenced by 66 grossly and microscopically normal embryos in the 15-75 mm crown-rump range. Male advancement was particularly pronounced in the younger (15-30 mm) embryos, both in the proximal hand region including the round bones of the wrist and in the distal hand region, comprising the metacarpals and phalanges. Thirty-four additional embryos, abnormal in implantation or development or representing spontaneous abortion similarly evidenced male advancement in the early hand skeleton.

As shown in 15 male and 17 female developmentally-normal, 6-9 week (15-47 mm crown-rump length) embryos, intercorrelations (communalities) involving both mesial and distal deciduous teeth and proximal and distal segments of the developing hand were systematically higher in female embryos than in male embryos, without exception, a finding in surprising accordance with postnatal dimensional and temporal development of the dentition and of the appendicular skeleton.