Sibling similarity in annual growth increments in schoolchildren from a rural community in Oaxaca, Mexico

Sibling similarity in annual growth increments was analysed in schoolchildren, aged 6-13 years, from a Zapotec-speaking, subsistence agricultural community in the Valley of Oaxaca in southern Mexico. Sibling correlations for 44 brother-brother, 44 sister-sister, and 110 unlike sex pairs were computed for 17 dimensions holding constant environmental effects, age difference between siblings, and the growth status of each sibling for the dimension. Correlations are negative or close to zero. The lack of similarity between siblings in annual growth increments perhaps reflects age-specific variation in a genotype-environment interaction with chronic undernutrition, the important mediating environmental variable.