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

(Non)Parallel Evolution

Parallel evolution across replicate populations has provided evolutionary biologists with iconic examples of adaptation. When multiple populations colonize seemingly similar habitats, they may evolve similar genes, traits, or functions. Yet, replicated evolution in nature or in the laboratory often yields inconsistent outcomes: Some replicate populations evolve along highly similar trajectories, whereas other replicate populations evolve to different extents or in distinct directions. To understand these heterogeneous outcomes, biologists are increasingly treating parallel evolution not as a binary phenomenon but rather as a quantitative continuum ranging from parallel to nonparallel. By measuring replicate populations’ positions along this (non)parallel continuum, we can test hypotheses about evolutionary and ecological factors that influence the extent of repeatable evolution. We review evidence regarding the manifestation of (non)parallel evolution in the laboratory, in natural populations, and in applied contexts such as cancer. We enumerate the many genetic, ecological, and evolutionary processes that contribute to variation in the extent of parallel evolution

The Population Genetic Signature of Polygenic Local Adaptation

Adaptation in response to selection on polygenic phenotypes may occur via subtle allele frequencies shifts at many loci. Current population genomic techniques are not well posed to identify such signals. In the past decade, detailed knowledge about the specific loci underlying polygenic traits has begun to emerge from genome-wide association studies (GWAS). Here we combine this knowledge from GWAS with robust population genetic modeling to identify traits that may have been influenced by local adaptation. We exploit the fact that GWAS provide an estimate of the additive effect size of many loci to estimate the mean additive genetic value for a given phenotype across many populations as simple weighted sums of allele frequencies. We first describe a general model of neutral genetic value drift for an arbitrary number of populations with an arbitrary relatedness structure. Based on this model we develop methods for detecting unusually strong correlations between genetic values and specific environmental variables, as well as a generalization of $Q_{ST}/F_{ST}$ comparisons to test for over-dispersion of genetic values among populations. Finally we lay out a framework to identify the individual populations or groups of populations that contribute to the signal of overdispersion. These tests have considerably greater power than their single locus equivalents due to the fact that they look for positive covariance between like effect alleles, and also significantly outperform methods that do not account for population structure. We apply our tests to the Human Genome Diversity Panel (HGDP) dataset using GWAS data for height, skin pigmentation, type 2 diabetes, body mass index, and two inflammatory bowel disease datasets. This analysis uncovers a number of putative signals of local adaptation, and we discuss the biological interpretation and caveats of these results.Comment: 42 pages including 8 figures and 3 tables; supplementary figures and tables not included on this upload, but are mostly unchanged from v

Human bony labyrinth is an indicator of population history and dispersal from Africa.

The dispersal of modern humans from Africa is now well documented with genetic data that track population history, as well as gene flow between populations. Phenetic skeletal data, such as cranial and pelvic morphologies, also exhibit a dispersal-from-Africa signal, which, however, tends to be blurred by the effects of local adaptation and in vivo phenotypic plasticity, and that is often deteriorated by postmortem damage to skeletal remains. These complexities raise the question of which skeletal structures most effectively track neutral population history. The cavity system of the inner ear (the so-called bony labyrinth) is a good candidate structure for such analyses. It is already fully formed by birth, which minimizes postnatal phenotypic plasticity, and it is generally well preserved in archaeological samples. Here we use morphometric data of the bony labyrinth to show that it is a surprisingly good marker of the global dispersal of modern humans from Africa. Labyrinthine morphology tracks genetic distances and geography in accordance with an isolation-by-distance model with dispersal from Africa. Our data further indicate that the neutral-like pattern of variation is compatible with stabilizing selection on labyrinth morphology. Given the increasingly important role of the petrous bone for ancient DNA recovery from archaeological specimens, we encourage researchers to acquire 3D morphological data of the inner ear structures before any invasive sampling. Such data will constitute an important archive of phenotypic variation in present and past populations, and will permit individual-based genotype-phenotype comparisons

Probabilidades Variacionales y Propensiones del Desarrollo: Un Estudio Filosófico del Azar en la Variación Evolutiva

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Filosofía, leída el 09/11/2020The ongoing debate over a possible extension of the explanatory corpus of evolutionary biology touches many aspects of philosophical interest, among which is the role that chance plays in its models and explanations. In particular, how evolutionary variation relates to chance seems to differ under the classical and the evo-devo perspectives. While some tools of the philosophy of probability and chance have been incorporated into important aspects of evolutionary biology, this discrepancy has not been considered from this perspective. In this dissertation, Iintend to bridge part of this gap by endorsing a conception of chance in the generation of evolutionary variation that is the result of incorporating several conceptual tools from the philosophy of probability and chance into different views over the nature of evolutionary variation. My aim is to clarify the distinct roles that chance in variation plays in the field of evo-devo as compared with classical evolutionary genetics. I depart from the construction of a suitable philosophical framework about the representative role of probabilities in evolutionary disciplines and the type of explanatory causes that are responsible for them...El actual debate sobre una posible extensión del corpus explicativo de la biología evolutiva recoge muchos aspectos de interés filosófico, entre los que se encuentra el rol del azar en sus modelos y explicaciones. En particular, la relación entre la variación evolutiva y el azar parece ser muy distinto bajo las perspectivas clásica y dela evo-devo. Mientras que algunas herramientas de la filosofía de la probabilidad y el azar han sido incorporadas en aspectos importantes de la biología evolutiva, esta disparidad no ha sido considerada desde esta perspectiva. En esta tesis, mi intención es aliviar parcialmente esta carencia defendiendo una noción de azar en la generación de la variación evolutiva que es el resultado de incorporar varias herramientas conceptuales de la filosofía de la probabilidad a distintas perspectivas sobre su naturaleza. Mi objetivo es clarificar los distintos roles que el azar en la variación juega en el campo de la evo-devo en comparación con la genética evolutiva clásica. Comienzo con la construcción de un marco filosófico que considera el rol representativo de la probabilidad en las disciplinas evolutivas y el tipo de causas explicativas que son responsables de ella...Fac. de FilosofíaTRUEunpu

Escaping Satiation in an Evolutionary Model of Structural Economic Dynamics

This paper presents the problem of satiation in relation to a model of evolutionary endogenous growth. The model represents an attempt to provide an evolutionary economic micro foundation to Pasinetti's scheme of the structural economic dynamics of a labour economy. Like this scheme the model deals with an economic system with a varying number of sectors, each of which is producing a consumption good. The goods are produced within consumer-producer firms which organise both production and consumption for their workers. Through innovative activities firms increase their productivity with respect to individual goods. The long-run consequence of this is that labour becomes available for the production of new consumption goods. If such goods are not provided to a sufficient degree, "technological unemployment" will emerge. If there is slow productivity development in the production of new goods, the overall rate of growth will slow down irrespectively of productivity growth in old sectors. Thus, to enhance long-term growth there is a need of "anticipatory R&D", i.e. R&D which produces designs for novel consumption goods and increases productivity in the production of these goods.Evolutionary modelling, endogenous growth and development, structural economic dynamics, satiation of demand, Robinson Crusoe.