Optimization of two-joint arm movements: a model technique or a result of natural selection?

The fossil record of early hominids suggests that their Arm length, and presumably stature and weight, had a tendency to increase. Using the minimum jerk principle and a related formulation of averaged specific power, ASP, with regard to selected two-joint Arm movements, the current paper explores relationships between ASP, hand trajectory length (or Arm length, or body mass) and mean movement speed, deriving relationships which indicate that ASP is proportional to cubic mean movement speed, but inversely proportional to hand trajectory length (or Arm length, or 1/3 power of body mass). Accordingly, an ;ecological niche' is modeled in a three-parameter space. Either ASP maximization for fixed movement time, or ASP minimization for fixed mean movement speed, taken as selective optimization criterion, allows the increasing of human Arm length during evolution, regardless of the arm-to-forearm length ratio.

Relevance of lunar periodicity in human spontaneous abortions.

The effect of the moon on human reproduction has been scarcely investigated and with controversial results. The present analysis describes a significant effect of extreme perigeal lunar positions on the number of hospitalized spontaneous abortions (n = 1,329) recorded at two university clinics and a public hospital at Padova, Italy, during the years 2000-2003. Spectral analysis evidenced a 205-day period which appears to be correlated with the 206-day periodicity in extreme lunar distances. Circa-septan and circa-annual periodicities were also observed. Peak significances were determined by a Monte Carlo approach (circa-septan and 205-day periodicities: p < 0.001; circa-annual periodicity: p < 0.05). Our study indicates that the occurrence of human abortions displays suggestive periodicities that may be of relevance for gynecological and obstetrical practice.