Palmar Creases: Classification, Reliability and Relationships to Fetal Alcohol Spectrum Disorders (FASD)

A normal human palm contains 3 major creases: the distal transverse crease; the proximal transverse crease; and the thenar crease. Because permanent crease patterns are thought to be laid down during the first trimester, researchers have speculated that deviations in crease patterns could be indicative of insults during fetal development. The purpose of this study was twofold: 1) to compare the efficacy and reliability of two coding methods, the first (M1) classifying both “simian” and Sydney line variants and the second (M2) counting the total number of crease points of origin on the radial border of the hand; and 2) to ascertain the relationship between palmar crease patterns and fetal alcohol spectrum disorders (FASD). Bilateral palm prints were taken using the carbon paper and tape method from 237 individuals diagnosed with FASD and 190 unexposed controls. All prints were coded for crease variants under M1 and M2. Additionally, a random sample of 98 matched (right and left) prints was selected from the controls to determine the reliabilities of M1 and M2. For this analysis, each palm was read twice, at different times, by two readers. Intra-observer Kappa coefficients were similar under both methods, ranging from 0.804-0.910. Inter-observer Kappa coefficients ranged from 0.582–0.623 under M1 and from 0.647–0.757 under M2. Using data from the entire sample of 427 prints and controlling for sex and ethnicity (white v. non-white), no relationship was found between palmar crease variants and FASD. Our results suggest that palmar creases can be classified reliably, but palmar crease patterns may not be affected by fetal alcohol exposure

Age-Independent Increases in Male Salivary Testosterone During Horticultural Activity Among Tsimane Forager-Farmers

Testosterone plays an important role in mediating male reproductive trade-offs in many vertebrate species, augmenting muscle and influencing behavior necessary for male-male competition and mating-effort. Among humans, testosterone may also play a key role in facilitating male provisioning of offspring as muscular and neuromuscular performance are deeply influenced by acute changes in testosterone. This study examines acute changes in salivary testosterone among 63 Tsimane men ranging in age from 16–80 (mean 38.2) years during one-hour bouts of treechopping while clearing horticultural plots. The Tsimane forager-horticulturalists living in the Bolivian Amazon experience high energy expenditure associated with food production, have high levels of parasites and pathogens, and display significantly lower baseline salivary testosterone than age-matched US males. Mixed-effects models controlling for BMI and time of specimen collection reveal increased salivary testosterone (p\u3c0.001) equivalent to a 48.6% rise, after one hour of tree chopping. Age had no effect on baseline (p=0.656) or change in testosterone (p=0.530); self-reported illness did not modify testosterone change (p=0.488). A comparison of these results to the relative change in testosterone during a competitive soccer tournament in the same population reveals larger relative changes in testosterone following resource production (tree chopping), compared to competition (soccer). These findings highlight the importance of moving beyond a unidimensional focus on changes in testosterone and male-male aggression to investigate the importance of testosterone-behavior interactions across additional male fitness-related activities. Acutely increased testosterone during muscularly intensive horticultural food production may facilitate male productivity and provisioning

Using Social Network Methods to Test for Assortment of Prosociality among Korean High School Students

<div><p>Assortative interaction among altruistic individuals is a necessary condition for the evolution of cooperation. The requirement for assortment holds regardless of whether a meta-population is subdivided into distinct and isolated subgroups or has ephemeral boundaries with a high migration rate. The assumption, however, is rarely tested directly. In this paper, we develop a method to test for assortment of prosociality in network-structured data. The method is applied to a friendship network collected from 238 Korean students attending the same high school. A mixing matrix was used to explore the presence of assortative friendship among more prosocial individuals. An exponential random graph model of network structure that accounts for additional observed relational propensities (higher-than-expected number of people nominating no friends) and sampling constraints (upper bound on friendship nominations) found that individual prosociality predicted friendship propensity, and that individuals with higher prosocial scores had a higher probability of befriending other more prosocial individuals. The results reveal that a considerable level of assortment of prosociality characterizes this population.</p></div

Contour plot for the prosocial edge covariate for ERGM 2.

<p>The numbers on the <i>x</i> and <i>y</i> axes correspond to the prosociality scores of the actors <i>i</i> and <i>j</i> and the corresponding point in the matrix represents the <i>edgecov</i> value for dyad (i, j), which equals the square root of the product of the two actors’ prosociality.</p

ERGM terms, with descriptive names and brief definitions.

<p>ERGM terms, with descriptive names and brief definitions.</p

Directed friendship network in a South Korean high school.

<p>Circles and arrows show individuals and friendship, respectively. The diameter of the circle shows relative level of individual prosociality (online version in color).</p

Types of ties when two types of individuals are present.

<p>Edges are directed and from rows to column. For example, tie type 2 includes the ties from more prosocial individuals to less prosocial ones. When our hypothesized form of assortment occurs, the number of tie type 1 should be more frequent than other types of ties.</p><p>Types of ties when two types of individuals are present.</p

Parameterization of the exponential random graph model (ERGM).

<p>* θ₁ is the default level of friendship without popularity and homophily; θ₂ is the effect of prosociality on outgoing ties (positive means individuals with higher prosociality have more numerous outgoing edges); θ₃ is the effect of prosociality on incoming edges; θ₄ is the effect of homophily (association with others exhibiting a similar level of prosociality).</p><p>Parameterization of the exponential random graph model (ERGM).</p