Skinfold measurements (triceps, subscapular, suprailiac and medial calf) in four samples (376 boys, 352 girs, 338 men and 380 women from rural Colombia) were subjected to principal components analysis to identify components of obesity and relative fat patterning. Three components emerged which were similar in the four samples: a first component of fatness explaining 70-80% of the variance and two fat pattern components each explaining 10-15% of the variance: trunk-extremity and upper-lower body. Fatness and the trunk-extremity pattern components changed with age in children (7-12 years), but none of the components changed with age in adults (25-60+). The fatter tended to be more patterned in both age groups. Canonical correlation analysis revealed that socioeconomic status was more related to fatness than to patterning. With the exception of brothers, all first degree relatives (sib, parent-off-spring) and spouses were correlated in fatness. Some of the correlations between relatives--usually sibs, but not spouses--were also significant for the pattern components, suggesting a genetic basis for the known stability of this characteristic (Garn, '55a). Principal components analysis is a useful multivariate alternative for quantitative studies of anthropometric patterning.

Geophagia, the eating of dirt, usually clay, has been recorded in every region of the world both as idiosyncratic behavior of isolated individuals and as culturally prescribed behavior of particular societies. The behavior has long been viewed as pathological by the medical profession, and it has been claimed to be both a cause and a consequence of anemia. While there is now reason to believe that the consumption of some clays may interfere with the absorption of elemental iron, zinc, and potassium, there is little evidence for the position that geophagia, especially its culturally prescribed form, is caused by anemia. These and other maladaptive consequences of clay consumption may be offset by the adaptive value of its antidiarrheal, detoxification, and mineral supplementation potentials.

A matrix is called persymmetric (Golub and Van Loan, Matrix Computations, The Johns Hopkins University Press, 1989) if it is symmetric across its lower-left to upper-right diagonal, with similar definitions for per-antisymmetric and per-Hermitian matrices. This note shows some useful eigenvalue and eigenvector properties of matrices with two symmetries, such as matrices which are symmetric and persymmetric.

No abstract