Men's Attraction to Women's Bodies Changes Seasonally

Association between meteorological variables and semen quality: a retrospective study

Spermatogenesis is a temperature-dependent process, and high summer temperatures have been linked to lower sperm concentration and count. However, reports describing the association between other meteorological variables and semen quality are scarce. This study evaluated the association between semen quality and temperature, humidity, pressure, apparent temperature (AT), temperature-humidity index (THI), simplified wet-bulb global temperature (sWBGT), and sunshine duration. Semen samples were obtained at the Laboratorio de Andrología y Reproducción (LAR, Argentina), from men undergoing routine andrology examination (n=11657) and computer-assisted sperm analysis (n=4705) following WHO 2010 criteria. Meteorological variables readings were obtained from the Sistema Meteorológico Nacional. Sperm quality parameters were negatively affected in summer when compared to winter. Additionally, there was a significant decrease in sperm kinematics between winter and spring. Branch and bound variable selection followed by multiple regression analysis revealed a significant association between semen quality and meteorological variables. Specifically, changes in sunshine duration and humidity reinforced the prognosis of semen quality. Highest/lowest sunshine duration and humidity quantiles resulted in decreased sperm concentration, count, motility, vitality and membrane competence, nuclear maturity, and sperm kinematics associated to highest sunshine duration and lowest humidity. Findings from this report highlight the relevance of environmental studies for predicting alterations in male reproductive health associated to variations in meteorological variables, especially considering the current climate changes around the planet due to global warming and its consequences for human health.

Like a jar of flies? A study of self-control in an organizational social dilemma with large stakes

We study the practice of self-control in an organizational social dilemma when the stakes are large, using 47 years of vital census data from 18^th century Sweden. From 1750 to 1800, eighty percent of Sweden lived in a simple-structure organization called a bytvång or village commons. The amount of resources a village family received was a function of their size. During this period, crop failures left the population facing starvation. Using autoregressive time-series modeling, we test whether the people of Sweden continued to take steps toward increasing the stress on the commons by marrying and birthing children or practiced self-control. We find evidence that the peasantry–with little education, archaic agricultural practices, strong barriers to abortion and infanticide, and pressures by the Church and State to procreate–were less likely to marry and birth children (in or outside of wedlock) when the quality of the previous year’s harvest was poor compared to when it was bounteous. Post hoc analyses support the idea that the reason behind declining fertility after a famine was human decision rather than human physiology. Our findings are consistent with the idea that human population growth is not a social dilemma called a collective trap–which has been the assumption for 50 years. Rather, human population growth may be an individual dilemma–suggesting that members of simple-structured organizations can unilaterally exercise self-control and manage resources through self-organizing.

The relationship of female physical attractiveness to body fatness

Aspects of the female body may be attractive because they signal evolutionary fitness. Greater body fatness might reflect greater potential to survive famines, but individuals carrying larger fat stores may have poor health and lower fertility in non-famine conditions. A mathematical statistical model using epidemiological data linking fatness to fitness traits, predicted a peaked relationship between fatness and attractiveness (maximum at body mass index (BMI) = 22.8 to 24.8 depending on ethnicity and assumptions). Participants from three Caucasian populations (Austria, Lithuania and the UK), three Asian populations (China, Iran and Mauritius) and four African populations (Kenya, Morocco, Nigeria and Senegal) rated attractiveness of a series of female images varying in fatness (BMI) and waist to hip ratio (WHR). There was an inverse linear relationship between physical attractiveness and body fatness or BMI in all populations. Lower body fat was more attractive, down to at least BMI = 19. There was no peak in the relationship over the range we studied in any population. WHR was a significant independent but less important factor, which was more important (greater r (2)) in African populations. Predictions based on the fitness model were not supported. Raters appeared to use body fat percentage (BF%) and BMI as markers of age. The covariance of BF% and BMI with age indicates that the role of body fatness alone, as a marker of attractiveness, has been overestimated.