Is a birth month dependence of human longevity influenced by half yearly changes in geomagnetics?

About-daily and about-yearly variations in organisms are commonly viewed as evolutionary adaptations to changes in the proximate environmental temperature and illumination. There is now ample evidence that a much broader time structure (chronome), long known to characterize the environment, is built into biological variables, from the level of an ecological niche revealed by demographic statistics to that of molecular genetics. While a molecular basis has been established for circadian rhythms, indirect evidence for some endogenicity had long been available by the persistence of rhythms with a period differing from the environmental cycle under constant conditions (free-running) (1, 2). Natural environmental factors have also been shown to play a critical role, notably in terms of synchronizing built-in rhythms (1-3). As reviewed elsewhere (4), non-photic as well as photic effects of the sun may play a role in shaping the element of multifrequency rhythms currently, and may have done so in the past, resulting in even broader chronomes with added elements of chaos and trends (4, 5). Non-photic signatures include, with the biological week (5), the about 10.5-year solar activity cycle, the about 21.0-year Hale bipolarity variation, and a prominent about half-year rhythm peaking at the equinoxes. This natural physical half-year characterizes various indices of geomagnetic activity (6-15) and may relate to the tilt angle of the earth's dipole axis toward and away from the sun, which reportedly is not constant according to Robert L. McPherron. It is particularly prominent when analyzed in Kp (5, 16, 17) by the population-mean cosinor method (18, 19).