Prevalence of Genetic versus Environmental Factors in Human Female Temporal Organization: Preliminary Analysis

Genetic diversity among ethnic groups is studied by comparing the genetic fingerprint of the examined groups. This index is constructed by aggregating the differential frequencies of various marker characteristics. Recent advances in the study of human biological rhythms may provide new indexes that will complement the genetic profile of a population. One of the rhythm parameters that is especially useful for this purpose is the acrophase (peak time location). The aim of the present study is to construct a rhythm profile based on acrophase distribution for various human groups and to estimate the contribution of genetic and environmental factors to that profile. The rhythm profiles were constructed by comparing the acrophases of 11 plasma hormones in women from three different ethnic-geographic populations (North Americans, Romanians, and Japanese) with reference to three age groups (adolescence-early postpuberty, young adulthood, and postmenopause). Genetic distances of these ethnic groups were determined by 14 genetic markers. Cluster and principal coordinates analyses were used to define the variation of the two parameters (genetic distances and acrophase dispersion). The analyses show that North Americans and Romanians are closer to each other with regard to both parameters and far apart from the Japanese. However, there was a difference between the variation presented by the first eigenvalue of the genetic profiles (94.5%) and that of the first eigenvalue of the acrophase pattern (69.1%), which means reduction in the variability (increased similarity) among the three ethnic groups according to the acrophase profiles. Therefore it is assumed that the reduction in the variability among the ethnic groups is influenced by the major compatible entraining signals (awakening time, sleep time, and meal time).