Stay or stray? Evidence for alternative mating strategy phenotypes in both men and women

In all comparative analyses, humans always fall on the borderline between obligate monogamy and polygamy. Here, we use behavioural indices (sociosexuality) and anatomical indices (prenatal testosterone exposure indexed by 2D : 4D digit ratio) from three human populations to show that this may be because there are two distinct phenotypes in both sexes. While males are more promiscuous and display higher prenatal testosterone exposure than females overall, our analyses also suggest that the within-sex variation of these variables is best described by two underlying mixture models, suggesting the presence of two phenotypes with a monogamous/promiscuous ratio that slightly favours monogamy in females and promiscuity in males. The presence of two phenotypes implies that mating strategy might be under complex frequency-dependent selection.     

Secretion of glucagon and insulin in hypophysectomized rats: effect of tolbutamide.

Normal and hypophysectomized (hypox) rats, fed ad libitum, received intraperitoneal injections of tolbutamide (75 mg/kg/day) or of saline for 6 weeks. 24 h after the last injection, blood samples were taken for glucose, insulin and glucagon determinations. In normal rats, tolbutamide treatment did not alter serum glucose, insulin and glucagon, although it suppressed the secretion of insulin and glucagon by the pancreatic islets. In hypox rats, tolbutamide decreased serum glucose and insulin, elevated serum glucagon and stimulated the secretion of glucagon, but not that of insulin by the pancreatic islets. In addition, tolbutamide treatment increased the glucagon response to arginine in normal, but not in hypox rats. The serum glucose response to arginine was decreased by tolbutamide treatment and by hypophysectomy and, thus, appeared independent of the glucagon rise or preexisting glucagon level. We conclude that tolbutamide treatment decreased the secretion of glucagon and insulin in normal rats and stimulated that of glucagon in hypox rats, perhaps because of the low levels of insulin in the serum and in the pancreas of the latter. Our results are compatible with the hypothesis that the pancreatic action of tolbutamide is influenced by the pituitary.     

Size and structure of freely forming conversational groups

Data from various settings suggest that there is an upper limit of about four on the number of individuals who can interact in spontaneous conversation. This limit appears to be a consequence of the mechanisms of speech production and detection. There appear to be no differences between men and women in this respect, other than those introduced by women’s lighter voices. Robin Dunbar, formerly Professor of BiologicalAnthropology at University College London, is currently Professor of Psychology at the University of Liverpool, where he carries out research on the behavior and ecology of human and nonhuman primates. Neil Duncan M.D. has recently qualified as a medical practitioner. Dan Nettle is carrying out doctoral research on the evolution of language.     

The site of active uptake of atmospheric water in larvae of Tenebrio molitor

Larvae starved and desiccated for 8 days will then take up water from 93% r.h., the gain ceasing by 7 days. The rate and amount of uptake were the same in those starved at 0% r.h. as in those starved at 53% r.h. Tying off the last abdominal segment prevents uptake while tying off the first abdominal segment allowed one-third as much gain as controls. This supports the theory that active uptake of atmospheric water is by way of the rectum and not the body cuticle. Because of the time taken to reach equilibrium, of the same uptake after exposure at 53% as after 0% r.h., and of a large overshoot in uptake, it is suggested that the phenomenon in this species is a by-product of drying the faeces and not a vital aspect of the physiology of water balance.     

Outward Extension of Spinules in Exine of Centrolepis aristata (Centrolepidaceae)

Spinules extend outwards 0.2 to 0.3 μm into the plasmodial tapetum during periods of rapid growth of microspores of Centrolepis. Before and after these intervals spinules commonly protrude only ca 0.05 μm above the surface of the tectum. The extended spinules have a rod shaped core ca 40 nm in diameter. The surface of the core is surrounded by loops ca 30 nm in diameter arranged in a regular pattern.     

Environmental determinants of intraspecific variation in body weight in baboons (Papio spp.)

Mean body weights of baboons differ considerably between populations for both males and females. This paper examines possible environmental causes of these differences. Mean annual rainfall and mean annual temperature are shown to be the two main factors responsible. Mean body weights for both sexes are a quadratic function of rainfall. Possible reasons why this might be so are examined.