Human populations differ in height. Recent evidence suggests that social networks play an important role in the regulation of adolescent growth and adult height. We further investigated the effect of physical connectedness on height. We considered Switzerland as a geographic network with 169 nodes (district capitals) and 335 edges (connecting roads) and studied effects of connectedness on height in Swiss conscript from 1884 - 1891, 1908 - 1910, and 2004 - 2009. We also created exponential-family random graph models to separate possible unspecific effects of geographic vicinity. In 1884 - 1891, in 1908 - 1910, and in 2004 - 2009, 1(st), 2(nd) and 3(rd) order neighboring districts significantly correlate in height (p < 0.01). The correlations depend on the order of connectedness, they decline with increasing distance. Short stature districts tend to have short, tall stature districts tend to have tall neighbors. Random network analyses suggest direct road effects on height. Whereas in 1884 - 1891, direct road effects were only visible between 1(st) order neighbors, direct road effects extended to 2(nd) and 3(rd) in 1908 - 1910, and in 2004 - 2009, also to 4(th) order neighbors, and might reflect historic improvements in transportation. The spatial correlations did not significantly change when height was controlled for goiter (1884 - 1889) and for median per capita income (2006), suggesting direct road effects also in goiter-allowed-for height and income-allowed-for height. Height in a district depends on height of physically connected neighboring districts. The association decreases with increasing distance in the net. The present data suggest that people can be short because their neighbors are short; or tall because their neighbors are tall (community effect on growth). Psycho-biological effects seem to control growth and development within communities that go far beyond our current understanding of growth regulation.

We test the hypothesis that differences in social status between groups of people within a population may induce variation in insulin-like growth factor-1(IGF-1) levels and, by extension, growth in height. This is called the community effect in height hypothesis. The relationship between IGF-1, assessed via finger-prick dried blood spot, and elite level sport competition outcomes were analysed for a sample of 116 undergraduate men and women. There was a statistically significant difference between winners and losers of a competition. Winners, as a group, had higher average pre-game and post-game IGF-1 levels than losers. We proposed this type of difference as a proxy for social dominance. We found no evidence that winners increased in IGF-1 levels over losers or that members of the same team were more similar in IGF-1 levels than they were to players from other teams. These findings provide limited support toward the community effect in height hypothesis. The findings are discussed in relation to the action of the growth hormone/IGF-1 axis as a transducer of multiple bio-social influences into a coherent signal which allows the growing human to adjust and adapt to local ecological conditions.