Evidence of directional and stabilizing selection in contemporary humans

Abstract

Modern molecular genetic datasets, primarily collected to study the biology of human health and disease, can be used to directly measure the action of natural selection and reveal important features of contemporary human evolution. Here we leverage the UK Biobank data to test for the presence of linear and nonlinear natural selection in a contemporary population of the United Kingdom. We obtain phenotypic and genetic evidence consistent with the action of linear/directional selection. Phenotypic evidence suggests that stabilizing selection, which acts to reduce variance in the population without necessarily modifying the population mean, is widespread and relatively weak in comparison with estimates from other species.

An evolutionary compass for detecting signals of polygenic selection and mutational bias

“…; Sanjak et al. ), polygenic adaptation (Turchin et al. ; Berg and Coop ), background selection (Charlesworth ; McVicker et al.…”

“…), but there is a need for models and inference tools integrating signatures of positive and negative selection on complex traits (Sanjak et al. ). Indeed, a natural way to model polygenic adaptation is to view stabilizing selection as a null process, with punctuated changes in the fittest trait value (herein called the “optimal trait value” or “trait optimum”) driving brief periods of adaptation (Barton ; Jain and Stephan ).…”

“…Natural selection and mutation shape variation within and between populations, but the evolutionary mechanisms shaping causal variation for human traits remain largely unknown. Studies of selection in humans have often focused on classic selective sweeps (Sabeti et al 2002(Sabeti et al , 2006Voight et al 2006;Hernandez et al 2011;Enard et al 2014), but other processes such as stabilizing selection (Gilad et al 2006;Sanjak et al 2018), polygenic adaptation (Turchin et al 2012;Berg and Coop 2014), background selection (Charlesworth 1994;McVicker et al 2009), negative selection (Boyko et al 2008), and soft sweeps (Messer and Petrov 2013;Schrider and Kern 2017) may also play an important role in shaping human diversity. Methods to detect selection under these more complex models are needed if we are to fulfill the promise of genomics to explain the evolutionary mechanisms driving the distribution of heritable traits in human populations (Pritchard et al 2010).…”

Cross-sex genetic correlations for fitness and fitness components: Connecting theoretical predictions to empirical patterns

“…These data provide clear evidence of sexually antagonistic selection in cases where female and male selection gradients of a trait exhibit opposite signs ( β f β m < 0; e.g., Cox and Calsbeek ; Morrissey ; Sanjaka et al. ), or when the angle between multivariate vectors of sex‐specific selection gradients is greater than orthogonal (i.e., θ > 90°; Lewis et al. ; Gosden et al.…”

“…Second, an even larger number of studies have published empirical estimates of female-and male-specific selection on homologous traits that both sexes express (Cox and Calsbeek 2009;Morrissey 2016;De Lisle et al 2018;Singh and Punzalan 2018). These data provide clear evidence of sexually antagonistic selection in cases where female and male selection gradients of a trait exhibit opposite signs (β f β m < 0; e.g., Cox and Calsbeek 2009;Morrissey 2016;Sanjaka et al 2017), or when the angle between multivariate vectors of sex-specific selection gradients is greater than orthogonal (i.e., θ > 90°; Lewis et al 2011;Gosden et al 2012;Stearns et al 2012). Note that sexually antagonistic genetic variation should be present under a broader set of conditions, as even minor misalignment between female and male directional selection (i.e., θ > 0°) should cause a fraction of standing genetic variation to have sexually antagonistic fitness effects (Connallon and Clark 2014).…”