Morphological and population genomic evidence that human faces have evolved to signal individual identity.

Facial recognition plays a key role in human interactions, and there has been great interest in understanding the evolution of human abilities for individual recognition and tracking social relationships. Individual recognition requires sufficient cognitive abilities and phenotypic diversity within a population for discrimination to be possible. Despite the importance of facial recognition in humans, the evolution of facial identity has received little attention. Here we demonstrate that faces evolved to signal individual identity under negative frequency-dependent selection. Faces show elevated phenotypic variation and lower between-trait correlations compared with other traits. Regions surrounding face-associated single nucleotide polymorphisms show elevated diversity consistent with frequency-dependent selection. Genetic variation maintained by identity signalling tends to be shared across populations and, for some loci, predates the origin of Homo sapiens. Studies of human social evolution tend to emphasize cognitive adaptations, but we show that social evolution has shaped patterns of human phenotypic and genetic diversity as well

Late Fathers\u27 Later Children: Reconceiving the Limits of Survivor\u27s Benefits in Response to Death-Defying Reproductive Technology

When Congress instructed the Social Security Administration to begin paying a social insurance benefit to widows and orphans in the 1930s, it simplified the process of determining an applicant\u27s relationship to an insured decedent in two significant ways: First, Congress ordered the agency to honor the intestate laws of each state when determining whether an applicant was actually the child of a decedent, and second, it ordered the agency to treat any child who could qualify as an intestate heir as if that child actually depended on the parent financially at the time of the parent\u27s death. Three-quarters of a century later, advances in reproductive technology make it possible for a child to be born decades after the death of one or both of her genetic parents. As the law begins to explore the rights and responsibilities of the parents who choose postmortem reproduction and the children whose lives come into being through those procedures, the heuristics that facilitated efficiency in the 1930s may yield unintended consequences. This Note explores some of those consequences and suggests minor alterations to the rules governing survivor\u27s-benefits eligibility intended to preserve the program\u27s social insurance function as reproductive technology transforms life after death from a hope or a fear into a choice

Evaluating circadian dysfunction in mouse models of Alzheimer\u27s disease: Where do we stand?

Circadian dysfunction has been described in patients with symptomatic Alzheimer\u27s disease (AD), as well as in presymptomatic phases of the disease. Modeling this circadian dysfunction in mouse models would provide an optimal platform for understanding mechanisms and developing therapies. While numerous studies have examined behavioral circadian function, and in some cases clock gene oscillation, in mouse models of AD, the results are variable and inconsistent across models, ages, and conditions. Ultimately, circadian changes observed in APP/PS1 models are inconsistent across studies and do not always replicate circadian phenotypes observed in human AD. Other models, including the 3xTG mouse, tau transgenic lines, and the accelerated aging SAMP8 line, show circadian phenotypes more consistent with human AD, although the literature is either inconsistent or minimal. We summarize these data and provide some recommendations to improve and standardize future studies of circadian function in AD mouse models

A single-nucleotide polymorphism in a Plasmodium berghei ApiAP2 transcription factor alters the development of host immunity

The acquisition of malaria immunity is both remarkably slow and unpredictable. At present, we know little about the malaria parasite genes that influence the host\u27s ability to mount a protective immune response. Here, we show that a single-nucleotide polymorphism (SNP) resulting in a single amino acid change (S to F) in an ApiAP2 transcription factor in the rodent malaria parasit

Coherent control of photocurrent in a strongly scattering photoelectrochemical system

A fundamental issue that limits the efficiency of many photoelectrochemical systems is that the photon absorption length is typically much longer than the electron diffusion length. Various photon management schemes have been developed to enhance light absorption; one simple approach is to use randomly scattering media to enable broadband and wide-angle enhancement. However, such systems are often opaque, making it difficult to probe photo-induced processes. Here we use wave interference effects to modify the spatial distribution of light inside a highly-scattering dye-sensitized solar cell to control photon absorption in a space-dependent manner. By shaping the incident wavefront of a laser beam, we enhance or suppress photocurrent by increasing or decreasing light concentration on the front side of the mesoporous photoanode where the collection efficiency of photoelectrons is maximal. Enhanced light absorption is achieved by reducing reflection through the open boundary of the photoanode via destructive interference, leading to a factor of two increase in photocurrent. This approach opens the door to probing and manipulating photoelectrochemical processes in specific regions inside nominally opaque media.Comment: 21 pages, 4 figures, in submission. The first two authors contributed equally to this paper, and should be regarded as co-first author

Device for dispersal of micrometer- and submicrometer-sized particles in vaccum

A simple, versatile device for dispersing micrometer‐ and submicrometer-sized particles in vacuum is described. The source allows control of particle size (0.5 μm≤l≤200 μm) and particle flux density up to roughly 107 cm−2 s−1. Several types of microparticles were successfully dispersed