Hormone-transfer theory proposes that the hormonal milieu of one twin may influence the other. In opposite-sex twins it has been proposed that hormonal transfer may produce a masculinizing effect in females. The second-to-fourth-finger ratio (2D:4D) has been proposed as an index of the level of prenatal androgens and could, theoretically, be used to detect hormone transfer. Previous examination...

CONTEXT Despite restrictive social norms, there is increasing evidence that youth in India engage in premarital romantic and sexual partnerships. However, information on how they initiate and build these relationships is scarce, even though it is vital for addressing the needs of young people. METHODS Attitudes toward and behavior within romantic partnerships were examined using data collecte...

BACKGROUND Sexual and reproductive health of young people has become a major health problem in recent decades. Recent and rapidly increasing Human Immune Deficiency Virus (HIV) rates show an urgent need for Sexually Transmitted Infections (STIs) and HIV prevention interventions in Nepal. OBJECTIVES This paper attempts to assess knowledge, attitude and behaviour on STIs/HIV/AIDS in the context...

BACKGROUND Knowing one's interpersonal relationship preferences can be tremendously helpful for medical students' lives. The purpose of this study was to examine the interpersonal needs in medical students. METHODS Between 2010 and 2015, a total of 877 students from four Korean medical schools took the Korean version of the Fundamental Interpersonal Relations Orientation - Behaviour (FIRO-B) ...

Separate sexes have evolved repeatedly from hermaphroditic ancestors in flowering plants, and thus select taxa can provide unparalleled insight into the evolutionary dynamics of sex chromosomes that are thought to be shared by plants and animals alike. Here we ask whether two octoploid sibling species of wild strawberry--one almost exclusively dioecious (males and females), Fragaria chiloensis,...

It has been proposed that selection has shaped the human mind to be predictably biased in domains where the costs of false-positive and false-negative errors have been asymmetrical throughout human evolutionary history. Using this logic, the current study predicts that men and women systematically overestimate the degree to which members of the opposite sex find their same-sex mating competitio...

Lummaa et al. (2007) presented historical data collected from twins born in Finland between 1734 and 1888 which suggested that females (N = 31) born as part of an opposite sex (OS) twin pair were 25% less likely to reproduce than female twins (N = 35) born as part of a same sex (SS) pair. They hypothesized that this reduction in fitness was due to masculinization of the female fetus via prenata...