Formalising the multidimensional nature of social networks

Individuals interact with conspecifics in a number of behavioural contexts or dimensions. Here, we formalise this by considering a social network between n individuals interacting in b behavioural dimensions as a nxnxb multidimensional object. In addition, we propose that the topology of this object is driven by individual needs to reduce uncertainty about the outcomes of interactions in one or more dimension. The proposal grounds social network dynamics and evolution in individual selection processes and allows us to define the uncertainty of the social network as the joint entropy of its constituent interaction networks. In support of these propositions we use simulations and natural 'knock-outs' in a free-ranging baboon troop to show (i) that such an object can display a small-world state and (ii) that, as predicted, changes in interactions after social perturbations lead to a more certain social network, in which the outcomes of interactions are easier for members to predict. This new formalisation of social networks provides a framework within which to predict network dynamics and evolution under the assumption that it is driven by individuals seeking to reduce the uncertainty of their social environment.Comment: 16 pages, 4 figure

Chemical evidence of the quantitative thiamine and riboflavin requirements of the rat during pregnancy and the development of the fetus

Two techniques have been investigated to determine more accurately the quantitative riboflavin needs of the rat during reproduction. One procedure, that of determining the deposition of riboflavin in the developing fetal and placental tissues at several intervals during pregnancy, has revealed a very rapid increase in the requirement for this factor during the last four days of pregnancy. Prior to this time, and in fact for the majority of the reproductive cycle, the full-grown rat appeared to have little need for riboflavin above that of the non-pregnant adult;The development of the placental tissue influenced the total need for riboflavin to a negligible extent;Metabolism studies conducted on pregnant and non-pregnant stock females maintained on a ration providing approximately 100 mcg. of riboflavin per day indicated that the diet provided a large surplus during the early portion of pregnancy and supplied some excess oven during the final days of gestation, as judged by the excretion of the vitamin by the kidneys. Females receiving this ration produced large litters of active young with satisfactory birth weights. The young were well stocked with riboflavin and there was no depletion of the maternal tissues during pregnancy;It was observed that stock females 92 days old were still accumulating body stores of riboflavin; those animals have a higher dietary need for riboflavin during reproduction than do older animals;Thiamine and riboflavin assays of the developing fetal tissues and those of the female rat during pregnancy indicated that the need for riboflavin was lose than that for thiamine. This quantitative relationship between the two vitamins Is particularly interesting in view of the present recommended allowances for the two vitamins during pregnancy in women;In the formulation of rations satisfactory for reproduction in rats, it appears that a daily intake of 100 mcg. of riboflavin is desirable during the last third of pregnancy when the demand for this vitamin reaches a maximum. This intake provides a considerable surplus during earlier phase of the pregnancy period;Thiamine requirements exceed those for riboflavin during pregnancy in the rat, although this relationship does not follow during maintenance of the adult female. The date from present study suggest that a daily intake of 125 mcg. thiamine is ample for reproduction during the period of maximum need. This amount supplies a large excess of the vitamin in the first half of the gestation period

The effect of various methods of extraction on the composition of fruit juice

Thesis (M.A.)--University of Kansas, Home Economics, 1930

Do Data from Large Personal Networks Support Cultural Evolutionary Ideas about Kin and Fertility?

The fertility decline associated with economic development has been attributed to a host of interrelated causes including the rising costs of children with industrialization, and shifts in family structure. One hypothesis is that kin may impart more pro-natal information within their networks than non-kin, and that this effect may be exacerbated in networks with high kin-density where greater social conformity would be expected. In this study, we tested these ideas using large personal networks (25 associates of the respondent) collected from a sample of Dutch women (N = 706). Kin (parents) were perceived to exert slightly more social pressure to have children than non-kin, although dense networks were not associated with greater pressure. In contrast, women reported talking to friends about having children to a greater extent than kin, although greater kin-density in the network increased the likelihood of women reporting that they could talk to kin about having children. Both consanguineal and affinal kin could be asked to help with child-care to a greater extent than friends and other non-kin. Overall, there was mixed evidence that kin were more likely to offer pro-natal information than non-kin, and better evidence to suggest that kin were considered to be a better source of child-care support

Why Machiavellianism Matters in Childhood: The Relationship Between Children's Machiavellian Traits and Their Peer Interactions in a Natural Setting

The current study investigated the association between Machiavellianism and children’s peer interactions in the playground using observational methods. Primary school children (N = 34; 17 female), aged 9 to 11 years, completed the Kiddie Mach scale and were observed in natural play during 39 recesses (average observed time = 11.70 hours) over a full school year. Correlations for boys revealed that Machiavellianism was related to more time engaging in direct and indirect aggression, being accepted into other peer groups, and accepting peers into their own social group. Correlations revealed that for girls, Machiavellianism was associated with lower levels of indirect aggression, less time being accepted into other groups and less time accepting and rejecting other children into their own group. This preliminary pilot study indicates that Machiavellianism is associated with children’s observed social behaviour and aims to promote future observational research in this area

Simulating the evolution of height in the Netherlands in recent history

The Dutch have a remarkable history when it comes to height. From being one of the shortest European populations in the 19th Century, the Dutch grew some 20 cm and are currently the tallest population in the world. Wealth, hygiene, and diet are well-established contributors to this major increase in height. Some have suggested that natural selection may also contribute to the trend, but evidence is weak. Here, we investigate the potential role of natural selection in the increase in height through simulations. We first ask what if natural selection was solely responsible for the observed increase in height? If the increase in average height was fully due to natural selection on male height, then across six consecutive generations, men who were two standard deviation above average height would need to have eight times more children on average. If selection acted only through those who have the opportunity to reproduce, then reproduction would need to be restricted to the tallest third (37%) of the population in order to give rise to the stark increase in height over time. No linear relationship between height and child mortality is able to account for the increase over time. We then present simulations based on previously observed estimates of partnership, mortality, selection and heritability and show that natural selection had a negligible effect (estimates from 0.07 to 0.36 cm) on the increase in height in the period 1850 to 2000. Our simulations highlight the plasticity of height and how remarkable the trend in height is in evolutionary terms. Only by using a combination of methods and insights from different disciplines, including biology, demography, and history are we potentially able to address how much of the increase in height is due to natural selection versus other causes.</p

The Reproductive Ecology of Industrial Societies, Part I Why Measuring Fertility Matters

Is fertility relevant to evolutionary analyses conducted in modern industrial societies? This question has been the subject of a highly contentious debate, beginning in the late 1980s and continuing to this day. Researchers in both evolutionary and social sciences have argued that the measurement of fitness-related traits (e.g., fertility) offers little insight into evolutionary processes, on the grounds that modern industrial environments differ so greatly from those of our ancestral past that our behavior can no longer be expected to be adaptive. In contrast, we argue that fertility measurements in industrial society are essential for a complete evolutionary analysis: in particular, such data can provide evidence for any putative adaptive mismatch between ancestral environments and those of the present day, and they can provide insight into the selection pressures currently operating on contemporary populations. Having made this positive case, we then go on to discuss some challenges of fertility-related analyses among industrialized populations, particularly those that involve large-scale databases. These include “researcher degrees of freedom” (i.e., the choices made about which variables to analyze and how) and the different biases that may exist in such data. Despite these concerns, large datasets from multiple populations represent an excellent opportunity to test evolutionary hypotheses in great detail, enriching the evolutionary understanding of human behavior

A Natural History of Repetition

The purpose of this study was to understand typically developing children’s repetitive behavior in a free-play, daycare setting. By studying repetition in a non-Montessori setting, we tested the assumption that repetition is a characteristic behavior of all young children and not limited to the Montessori environment. Although Maria Montessori identified repetition during her observations, there is little empirical evidence to support her claim: most research has considered repetition in terms of psychopathology. We collected naturalistic observational data on 31 3- to 6-year-old children for a total of 101 hours to investigate the frequency, contexts, and structure of repetitive bouts. Multilevel model results suggest the ubiquity of repetition, as all children in the study engaged in motor repetition. Furthermore, repetition occurred throughout all free-play activities (construction, animation, fantasy play, rough-and-tumble play, and undirected activity), although repetition was not equally distributed across activities. Motor repetition was not equal across ages either; younger children engaged in more motor repetition than did older children. To understand the structure of repetition, our study also looked at the length of repetition bouts, which ranged from 2 to 19 repetitions and averaged 2.86 repetitions per bout. This natural history of repetition is an influential starting point for understanding the role of repetition in development and is informative to both Montessori and non-Montessori early childhood educators

The ‘strength of weak ties’ among female baboons : fitness-related benefits of social bonds

Thanks to Cape Nature Conservation for permission to work at De Hoop, and to all the graduate students and field assistants who contributed to our long-term data-base. LB was supported by NSERC Canada Research Chair and Discovery Programs; SPH was supported by the NRF (South Africa) and NSERC Discovery Grants during the writing of this manuscript. We are grateful to one anonymous reviewer and, in particular, Lauren Brent for invaluable feedback on earlier drafts of our manuscript.Peer reviewedPostprin