OBJECTIVES This study examined the changes in running performance and the sex differences between women and men in 24-hour ultra-marathons held worldwide from 1977 to 2012. METHOD Changes in running speed and ages of the fastest 24-hour ultra-marathoners were determined using single- and multi-level regression analyses. RESULTS From 1977 to 2012, the sex differences in 24-hour ultra-maratho...

The aim of this study was to describe the annual activity cycle, the sex ratio, and the relationship between the weather variables and activity density of the 16 most abundant carabid species of a typical southeastern region of Pampasia, Argentina. The study focused on the southernmost Celtis ehrenbergiana (Klotzsch) Liebmann ( = C. tala Guillies ex Planch) native forest of the region, from Mar...

Skews in the human sex ratio at birth have captivated scientists for over a century. The accepted average human natal sex ratio is slightly male biased, at 106 males per 100 females or 51.5 per cent males. Studies conducted on a localized scale show that sex ratios deviate from this average in response to a staggering number of social, economical and physiological variables. However, these patt...

Social learning provides an effective route to gaining up-to-date information, particularly when information is costly to obtain asocially. Theoretical work predicts that the willingness to switch between using asocial and social sources of information will vary between individuals according to their risk tolerance. We tested the prediction that, where there are sex differences in risk toleranc...

Few sex differences in regret or counterfactual thinking are evident in past research. The authors discovered a sex difference in regret that is both domain-specific (i.e., unique to romantic relationships) and interpretable within a convergence of theories of evolution and regulatory focus. Three studies showed that within romantic relationships, men emphasize regrets of inaction over action (...

OBJECTIVE The higher incidence of man-to-woman transsexuals compared to woman-to-man transsexuals varies markedly from country to country. This is the first survey of the sex ratio to be made in Germany. METHOD It covers 1785 patients who between 1964 and 1998 were diagnosed as transsexual at the four largest German centres offering treatment. RESULTS From 1970 to 1994 the sex ratio remaine...

This paper has the three objectives of attempting to replicate a previous study in which it was found that males have substantially greater general knowledge in most fields or domains than females, and of determining how far sex differences in general knowledge are a function of differences in either Gf (fluid intelligence), or experience. The results confirmed the previous study to the effect ...

Mothers that experience different individual or environmental conditions may produce different proportions of male to female offspring. The Trivers-Willard hypothesis, for instance, suggests that mothers with different qualities (size, health, etc.) will use different sex ratios if maternal quality differentially affects sex-specific reproductive success. Condition-dependent, or facultative, se...

Under many circumstances, it might be adaptive for parents to bias the investment in offspring in relation to sex. Recently developed molecular techniques that allow sex determination of newly hatched offspring have caused a surge in studies of avian sex allocation. Whether females bias the primary brood sex ratio in relation to factors such as environmental and parental quality is debated. Pro...

New findings in the platypus and Drosophila pseudoobscura illustrate, yet again, that the sex chromosomes seem never to stop evolving. Degeneration processes lead to a continual loss of genes and gene activity on the Y chromosome, and complete loss of Y-linked genes is possible if autosomal genes take over control of male fertility - though addition of new material to the sex chromosomes may st...