Title: Living together as a factor in family-line resemblances.
Abstract: Since people who live together tend to share a common diet and habits of energy expenditure it is reasonable to expect similarities in serum and urinary vitamin levels, in hemoglobins and hematocrits, blood lipids, fatness levels and over time in selected outer dimensions. This expectation is confirmed by dietary, biochemical and anthropometric comparisons of genetically-unrelated individuals who live together, i.e. parents and children, siblings, spouses, adoptive parentchild pairs and unrelated siblings. Such similarities are notable for vitamins A and C, serum cholesterol, outer fatness and for long-term fatness changes (A fat) of both geneticallyrelated and genetically-unrelated family members. Even stature suggests a long-term effect of living together. Collecting these similarities as examples of the cohabitational effect , it is suggested that many family-line resemblances are inflated by the results of living together, and that resemblances between contiguous populations may also reflect similarities in energy intake, energy expenditure, diet and nutrition. It is common observation that dimensional similarities between human beings decrease as the degree of relationship becomes less. Thus, dizygotic twins are less alike dimensionally than monozygotic twins, cousins resemble each other less than do full siblings, and populations that are more remote are also less alike than are contiguous groups. Provided that the samples are large enough to yield valid estimates of r and provided that age-effects are minimized by using residuals from segmented regressions or age-specific correlations, this general statement holds within acceptable limits. Indeed, the strength of dimensional similarities and the decrease with decreasing relationship follows expectation, nature obligingly agreeing with mathematical art. From such observations, which progress along regular and lawful lines, it has been possible to infer that geographic distance and distance reasonably agree, with major taxonomic and evolutionary implications. Clines of stature or head size have been accorded taxonomic meaning in some classificatory systems. Gradients running from equator to pole and following the mean annual temperature have been attributed to climatic selection. It is reasonable to assume that closely-related people 1Center for Human Growth and Development and Department of Anthropology, University of Michigan, Ann Arbor, Michigan 48109. Human Biology , December 1979, Vol. 51, No. 4, pp. 565-587. ® Wayne State University Press, 1979 This content downloaded from 157.55.39.94 on Sun, 17 Apr 2016 06:09:22 UTC All use subject to http://about.jstor.org/terms 566 Stanley M. Garn, Patricia E. Cole and Stephen M. Bailey are subject to the same selective pressures, helping to keep them dimensionally alike, and that more remote groups are exposed to selective forces that make them more different. But it is also true that people who live together share energy and nutrient intakes in common, levels of energy expenditure in common and that their share a comparably high or comparably low caloric surplus, then available for both growth and storage as fat. To the extent that people who live together share a common diet, they also share minerals, trace-elements and micro-nutrients. As particular, polar, examples we Americans derive more than half of our calories from fat but the Bundi derive a scant ten percent. It has not escaped notice that the tallest and heaviest of human groups simultaneously enjoy a high caloric intake, a high protein intake, a high fat intake, a large gross national product (G.N. P. ) and a high per-capita income. It has not escaped notice that the little people of the world are also low in these same comparative measures. To some extent, therefore, dimensional similarities among related individuals may reflect more than genes held in common. To some extent both parent-child and sibling similarities in both outer and inner measurements may be inflated by common patterns of eating and working and exercising. To some extent genetic distance and geographical distance may correspond, in anthropometric similarity, simply because people in the same household, the same city and the same state (or district) share access to calories, attitudes toward eating, habits of exercise and reductions in absorptive efficiency. Newborn infants are not immune from these same strictures. Sibling neonates have enjoyed the same mothers as sources of nutrients and calories, placentas of comparable size, and maternal habits of eating and exercising. They may have been programmed in utero to become large or small in extra-uterine life. We even now know that size at birth is a determinant of subsequent size, reiterating the previous paragraphs but retreating further back in developmental time, and including maternal size and fatness as determinants of later dimensional resemblances. Now all of these statements, however reasonable, would be purely speculative without hard data to cite. To quote Charles Darwin, Any fool can speculate. What is needed is hard data, on successive levels of dietary and nutrient similarity, on serum and urinary values in parents and children, and other indications that people who live together do resemble each other (as might be expected). What is needed, further, is evidence that genetically-unrelated individuals living together do resemble each other in what they eat, in blood and urinary variables, and This content downloaded from 157.55.39.94 on Sun, 17 Apr 2016 06:09:22 UTC All use subject to http://about.jstor.org/terms Living Together and Family -Line Resemblances 567 ultimately in a variety of anthropometric diameters. What is needed is evidence that genetically-unrelated men and women, parents and children and brothers and sisters do come to resemble each other dimensionally because of what may be called the cohabitational effect. In discussing, describing and also documenting the cohabitational effect, let one point be totally clear. This is no essay on genetics versus environment. As Human Biologists we know both to be important. Nor is it any attempt to separate one from the other, in human beings, where only a fraction of the environmental sources of dimensional variance can be exploited in usual family-line context, or in a community or in a county. Rather it is an attempt, supported by very considerable data (most of it newly presented here) to provide some indication of resemblances in dietary intakes, serum and urinary values, fatness levels and dimensions that come about through living together. Elsewhere we have described the strategies of using geneticallyunrelated individuals living together husbands and wives, parents and their adopted children, genetically-unrelated siblings and others. Elsewhere we have explored family-line similarities or synchronies in fatness-gain or fatness loss, using the living-together model. The purpose here is to present largely unpublished data of massive size showing and documenting the cohabitational effect. (See also Garn et al. 1976a, 1979a, b, c, d). Dietary Similarities Among People Who Live Together The first point to document, then, is the extent of dietary similarity between individuals who are living together. Though cognizant of many factors that should make for similarity (such as meals shared in common) and factors that may reduce dietary similarity (such as individual food preferences) actual data merit priority over deliberation. So the first set of data (Table 1) involves husband-wife comparisons, using complete 7-day dietary diaries, and detailed analyses (Garn and Pao, 1968; Garn, 1970). These comparisons, for calories, protein, calcium and alcohol in 104 husband-wife pairs, reveal systematic positive correlations for all variables considered from milk as a percent of calories, to total calories, to alcohol consumption (expressed as calories and percent of total calories). Without attempting to over-interpret the data, involving more than 1400 persondays, two generalizations are immediately possible. First there is reasonable husband-wife agreement in caloric intake (r = 0.45) for an average of 18 out of 21 meals shared in common. Second, and of major interest to This content downloaded from 157.55.39.94 on Sun, 17 Apr 2016 06:09:22 UTC All use subject to http://about.jstor.org/terms 568 Stanley M. Garn, Patricia E. Cole and Stephen M. Bailey
Publication Year: 1979
Publication Date: 1979-12-01
Language: en
Type: article
Indexed In: ['pubmed']
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Cited By Count: 101
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