Friday, May 30, 2014

Plain faces are more expressive

My colleagues Sharlene Santana, Rui Diogo, and I have a new paper in Biology Letters entitled "Plain faces are more expressive: comparative study of facial colour, mobility and musculature in primates." Here's the abstract.
Facial colour patterns and facial expressions are among the most important phenotypic traits that primates use during social interactions. While colour patterns provide information about the sender's identity, expressions can communicate its behavioural intentions. Extrinsic factors, including social group size, have shaped the evolution of facial coloration and mobility, but intrinsic relationships and trade-offs likely operate in their evolution as well. We hypothesize that complex facial colour patterning could reduce how salient facial expressions appear to a receiver, and thus species with highly expressive faces would have evolved uniformly coloured faces. We test this hypothesis through a phylogenetic comparative study, and explore the underlying morphological factors of facial mobility. Supporting our hypothesis, we find that species with highly expressive faces have plain facial colour patterns. The number of facial muscles does not predict facial mobility; instead, species that are larger and have a larger facial nucleus have more expressive faces. This highlights a potential trade-off between facial mobility and colour patterning in primates and reveals complex relationships between facial features during primate evolution.
You can access the article here (Subscription required until May 2015).

Tuesday, September 3, 2013

Survival of the shortest (allele)

My colleague Lauren Brent and I have contributed a hypothesis & theory paper entitled "On the evolution of the serotonin transporter linked polymorphic region (5-HTTLPR) in primates" to a research topic in the open access journal Frontiers in Human Neuroscience. The paper has been accepted and should be online soon. Here is the abstract:

Some allelic variants of the serotonin transporter linked polymorphic region (5-HTTLPR) result in lower levels of expression of the serotonin transporter gene (SLC6A4). These low-expressing (LE) alleles are associated with mental-health disorders in a minority of humans that carry them. Humans are not the only primates that exhibit this polymorphism; other species, including some monkeys and apes, also have LE and high-expressing (HE) variants of 5-HTTLPR. We propose a behavioral genetic framework to explain the adaptive evolution of this polymorphism in primates, including humans. We hypothesize that both LE and HE alleles are maintained by balancing selection in species characterized by fluctuating levels of within-group competition. More specifically, we propose that LE carriers benefit from their hypervigilant tendencies during periods of elevated social competition, whereas HE homozygotes cope best when competition levels do not deviate from the norm. Thus, both alleles have long-term benefits when competition levels fluctuate substantially over time within a social group. We describe this hypothesis in detail and outline a series of predictions to test it. Some of these predictions are supported by findings in the current literature, while others remain areas of future research.

UPDATE (11/8/13): Our article is now online and freely available here.