Genetic genealogy comes of age: advances in the use of deep-rooted pedigrees in human evolutionary research (video)
Author(s): Larmuseau, MHD, Van Geystelen, A, Decorte, R
Research on the recent human evolution will benefit from the implementation of extended genetic genealogical data. The approach to combine deep-rooted pedigrees with genetic information advances the understanding of changes in the human population genetic structure during the last centuries. This recent advance is mainly based on the extensive growth of whole genome sequencing data and available genealogical data of high quality. Moreover, according to the latest genetic genealogical research the historical non-paternity rate in Western Europe is estimated around 1% per generation within the last four centuries, which means that the expected relationship between the legal genealogy and the genetics of DNA donors exists. Therefore, genetic genealogical data will help with three research aims of human evolutionary studies: (I) detecting signals of (past) population stratification and interpreting the population structure in a more objective manner, (II) obtaining the time scale and impact of particular detected gene flow events more accurately and (III) determining temporal genetic differentiation within a population by combining in-depth pedigree data with haploid markers. Each of these research aims will be discussed with examples of the human population in Flanders (Western Europe). At the end, we will discuss the advantages and pitfalls of using genetic genealogy within studies on human evolutionary genomics.
Detection of polygenic selection at different evolutionary levels (video)
Author(s): Excoffier L, Daub J
Most approaches aiming at finding genes involved in adaptive events have focused on the detection of outlier loci, which resulted in the discovery of individually ´significant´ genes with strong effects. However, a collection of small effect mutations could have a large effect on a given biological pathway that includes many genes, and such a polygenic mode of adaptation has not been systematically investigated in humans or other mammals. We therefore propose to evidence polygenic selection by detecting signals of adaptation at the pathway or gene set level instead of analyzing single independent genes. Using a gene-set enrichment test, we identify genome-wide signals of recent adaptation among human populations as well as more ancient signals of adaptation in the human lineage and in primates.
A genome-wide scan for relaxation of constraints in the human lineage affecting specific functional processes (video)
Author(s): Somel, M, Wilson-Sayres, M, Jordan, G, Huerta-Sanchez, E, Fumagalli, M, Ferrer-Admetlla, A, Nielsen, R
Changes in the subsistence mode of a species can lead to adaptive evolution of new functions, while it can also cause relaxed negative selection in previously essential functions. While positive selection in humans has been intensely studied, functional processes subject to relaxed constraints in the human lineage remain largely unknown. Here we present a framework for detecting relaxation of selective constraints that affect a particular functional process specifically in one taxon. Jointly using human and chimpanzee population genomic data with mammalian comparative genomic data, we identify olfactory receptors and proteasome subunits as candidates of relaxed constraints in humans: both gene sets contain high frequency non-synonymous mutations in humans while having conserved amino-acid sequences across other mammals. We further discuss the possible underlying causes of this signal.
Selection on penis size, body shape and height in humans: a simple multivariate method to quantify female preferences based on male physical attractiveness (video)
Author(s): Mautz, BS, Jennions, MD, Peters, RA, Wong, BBM
Compelling evidence from many animal taxa indicates that male genitalia are often under post-copulatory sexual selection for characteristics that increase a male’s relative fertilization success under sperm competition. There could, however, also be direct pre-copulatory female mate choice based on male genital traits. Before clothing, the non-retractable human penis would have been conspicuous to potential mates. This, in combination with claims that humans have a large penis for their body size compared to other primates, has generated suggestions that human penis size partly evolved due to female choice. We presented women with digitally projected fully life-size, computer-generated animations of male figures to quantify the (interactive) effects of penis size, body shape and height on female assessment of male sexual attractiveness. We generated 343 male figures that each had one of seven possible values for each of the three test traits (7x7x7 = 343). All seven test values per trait were within two standard deviations of the mean based on a representative sample of males. We calculate response (fitness) surfaces based on the average attractiveness rank each of the 343 male figure received. We also calculated individual response surfaces for 105 women (each women viewed 53 figures). Both methods yielded almost identical results. We discuss our finding in the context of previous studies that have taken a univariate approach to quantify female preferences. We discuss the hypothesis that pre-copulatory sexual selection might play a role in the evolution of genital traits.
Quantitative genetic variation, selection and secular change of skull shape in humans
Author(s): Klingenberg, C, Martínez-Abadías, N, Esparza, M, Sjøvold, T, Hernández, M
The combined use of geometric morphometrics and quantitative genetics provides a set of powerful tools for obtaining quantitative information that is crucial for many important questions concerning the evolution of shape. In particular, the demographic information that is available for human populations make humans a unique study system for studying the mechanisms of evolutionary change in morphological traits. We investigate skull shape in the population of Hallstatt (Austria), where a collection of human skulls with associated records offer a unique opportunity for such studies. We use an individual-based statistical model to estimate the genetic covariance matrix, and characterize selection using fitness estimates from demographic data. We find clear evidence for directional selection, but not for nonlinear selection (stabilizing or disruptive selection). The predicted response to this selection, computed with genetic parameters from the population, does not match the estimate of secular change over the 150-year range of the data. We discuss possible reasons for the mismatch.