The latest in chinology

Our PLoS One paper on geographic variation in chin shape has received a bit of media attention. Here are some of the highlights.

Do Hollywood chins drive sexual selection? - LA Times

Leading man's chin: universally hot or not? - NPR

Chin up! Strong jaws are not the only type of chin people find attractive (bad news for Brad Pitt) - DailyMail UK

Thanks Ben!

My new project is funded by a Franklin Research Grant from the American Philosophical Society. The title of the project is "Genetic basis of facial expression in female rhesus macaques (Cayo Santiago, Puerto Rico)." Here is a brief description of what we plan to do.

We propose to investigate the genetic basis of facial expressiveness in female rhesus macaques (Macaca mulatta). We will test the hypothesis that facial expressiveness is a genetically heritable trait by focusing on two main predictions. First, if individual differences in facial expressiveness are heritable, then closely related females will be more similar in expressiveness than distantly related females. Second, if facial expressiveness is influenced by genetics, then differences in genotype will be associated with individual differences in expressiveness. We will focus on two candidate genes associated with emotion regulation in humans, a length polymorphism within the promoter region (5-HTTLPR) of the serotonin transporter gene (SLC6A4), and a variable insertion in the gene encoding tryptophan hydroxylase (TPH2).

This project will be carried out in collaboration with Lauren Brent and Michael Platt (Duke U.).

An open mouth threat display from a female rhesus macaque

Evolving insular cortices

I am coauthor of a forthcoming paper in the Journal of Human Evolution entitled "A volumetric comparison of the insular cortex and its subregions in primates." The lead author Amy Bauernfeind is a student in Chet Sherwood's lab. Here's the abstract:

The neuronal composition of the insula in primates displays a gradient, transitioning from granular neocortex in the posterior-dorsal insula to agranular neocortex in the anterior-ventral insula with an intermediate zone of dysgranularity. Additionally, apes and humans exhibit a distinctive subdomain in the agranular insula, the frontoinsular cortex (FI), defined by the presence of clusters of von Economo neurons (VENs). Studies in humans indicate that the ventral anterior insula, including agranular insular cortex and FI, is involved in social awareness, and that the posterodorsal insula, including granular and dysgranular cortices, produces an internal representation of the body's homeostatic state. We examined the volumes of these cytoarchitectural areas of insular cortex in 30 primate species, including the volume of FI in apes and humans. Results indicate that the whole insula scales hyperallometrically (exponent = 1.13) relative to total brain mass, and the agranular insula (including FI) scales against total brain mass with even greater positive allometry (exponent = 1.23), providing a potential neural basis for enhancement of social cognition in association with increased brain size. The relative volumes of the subdivisions of the insular cortex, after controlling for total brain volume, are not correlated with species typical social group size. Although its size is predicted by primate-wide allometric scaling patterns, we found that the absolute volume of the left and right agranular insula and left FI are among the most differentially expanded of the human cerebral cortex compared to our closest living relative, the chimpanzee.

UPDATE (3/13/13): The article is available online here (subscription required). Email me if you would like a PDF (seth dot dobson at dartmouth dot edu).