Human Evolutionary Genetics (2ndedition). By Mark Jobling, Edward Hollox, Matthew Hurles, Toomas Kivisild, and Chris Tyler‐Smith. pp. Get Instant Access to PDF File: #ba Human Evolutionary Genetics By Mark Jobling, Edward Hollox, Toomas Kivisild, Chris Tyler Smith. Request PDF on ResearchGate | On Jan 1, , Mark Jobling and others published Human Evolutionary Genetics: Origins, Peoples & Disease.
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PDF | 65 minutes read | Wide-ranging and inclusive, this text provides an invaluable to phenotypic and genetic variation within and between human populations, Food supply is a major selective force in humans, in our evolutionary history. Human Evolutionary Genetics (2 nd edition). By Mark Jobling American Journal of Human Biology 26(4): Name: ajhbpdf. Size: KB. While one might be led to believe that this book would more suitably fit the interests of researchers, whose productivity is relentlessly leveraged according to .
Here the gene trees are incongruent to the species tree. When three species are fairly closely related to each other like human, chimpanzee and gorilla , the trees obtained from DNA sequence data may not be congruent with the tree that represents the speciation species tree. The shorter internodal time span TIN the more common are incongruent gene trees. The effective population size Ne of the internodal population determines how long genetic lineages are preserved in the population.
A higher effective population size causes more incongruent gene trees.
Therefore, if the internodal time span is known, the ancestral effective population size of the common ancestor of humans and chimpanzees can be calculated. When each segment was analyzed individually, 31 supported the Homo-Pan clade, 10 supported the Homo-Gorilla clade, and 12 supported the Pan-Gorilla clade. Using the molecular clock the authors estimated that gorillas split up first 6.
The internodal time span is useful to estimate the ancestral effective population size of the common ancestor of humans and chimpanzees. A parsimonious analysis revealed that 24 loci supported the Homo-Pan clade, 7 supported the Homo-Gorilla clade, 2 supported the Pan-Gorilla clade and 20 gave no resolution.
Additionally they took 35 protein coding loci from databases. Of these 12 supported the Homo-Pan clade, 3 the Homo-Gorilla clade, 4 the Pan-Gorilla clade and 16 gave no resolution. This value is not as high as that from the first study Takahata , but still much higher than present day effective population size of humans. Only a very tiny fraction of those fixed differences gave rise to the different phenotypes of humans and chimpanzees and finding those is a great challenge.
The vast majority of the differences are neutral and do not affect the phenotype. All are thought to have played some part in human evolution. Gene loss[ edit ] Many different mutations can inactivate a gene, but few will change its function in a specific way. Inactivation mutations will therefore be readily available for selection to act on. Gene loss could thus be a common mechanism of evolutionary adaptation the "less-is-more" hypothesis.
Genes involved in chemoreception and immune response are overrepresented.
Keratins are a major component of hairs. Humans still have nine functional type I hair keratin genes, but the loss of that particular gene may have caused the thinning of human body hair.
Based on the assumption of a constant molecular clock, the study predicts the gene loss occurred relatively recently in human evolution—less than years ago, but both the Vindija Neandertal and the high-coverage Denisovan sequence contain the same premature stop codons as modern humans and hence dating should be greater than years ago.
They estimated that the mutation that led to the inactivation a two base pair deletion occurred 2. The period that followed was marked by a strong increase in cranial capacity , promoting speculation that the loss of the gene may have removed an evolutionary constraint on brain size in the genus Homo. The loss of this gene is speculated to have reduced the lethality of bacterial infection in humans.
Human-specific DNA insertions[ edit ] When the human genome was compared to the genomes of five comparison primate species, including the chimpanzee, gorilla, orangutan, gibbon, and macaque, it was found that there are approximately 20, human-specific insertions believed to be regulatory.
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Here, we applied the same polygenic enrichment approach in conjunction with a more recent and comprehensive post-Neanderthal selective sweep index 36 to study the evolutionary aspects of educational attainment and cognitive function, and determine enrichment in genomic regions that may have undergone recent positive selection in humans.
To this end, we analysed genome-wide association GWAS summary statistics for two measures of educational attainment, college completion College 37 and years of educational attainment EduYears 38 , and two measures of fluid intelligence from two studies of general cognitive ability GCA 39 , We hypothesized that higher cognitive functions are a product of human evolution in line with previous theories We compared the cognitive phenotypes to height and body mass index BMI , two human traits with GWASs of similar size, to assess the specificity of this enrichment.
The PNSS index defines regions that have undergone positive selection in humans after the separation of the human and Neanderthal lineages. We specifically investigated association enrichment, visualized as an upward deflection in fold enrichment plots and a leftward deflection in Q-Q plots for details, see Methods.
The fold enrichment plots Fig. S1 suggest that the genetic variants in regions that may have undergone positive selection in humans, i. Figure 1 Fold enrichment plots of phenotypes stratified according to Neanderthal selective sweep score. Full size image To test the significance of the enrichment, we conducted a stratified LD score regression analysis The LD score regression method provides an estimate of the fold enrichment associated with these evolutionary regions, and thus an estimate of enrichment Table 1 Post-Neanderthal selective sweep enrichment.
Full size table To further detail the specificity of the enrichment, we used summary statistics from height and BMI GWASs, which involved sample sizes comparable to or larger than the ones available to the cognitive GWASs. While height and BMI have been associated with some evolutionary pressure in humans 46 , 47 , we expect them to show a less pronounced enrichment than the cognitive phenotypes since they are less likely to be human specific compared to cognitive function.
Our fold enrichment plots Fig. The fold enrichment test statistics BMI: 1. Given the importance of genes involved in brain function for the phenotypes of interest, and their evolutionary relevance, we performed additional analyses targeting genes with high expression levels in the brain brain genes Fig.
Brain genes in HD regions show more pronounced association enrichment than any brain genes or any SNPs in HD regions in the fold enrichment plots. Figure 2 Enrichment of associations with various traits stratified according to their affiliation to Post-Neanderthal selective sweep regions and brain genes. Plots are shown for variants annotated to human divergent regions HD , variants annotated to generic genes Any , variants annotated to genes with high expression in the brain Brain , variants in HD regions annotated to genes with high expression in brain HDBrain , and all variants All SNPs.
The HDBrain category is enriched upward deflection compared with the other categories i. Full size image Discussion Applying our Neanderthal polygenic enrichment approach to recent large GWAS data on cognitive traits 37 , 38 , 39 , 48 , we investigated the hypothesis that higher cognitive functions in humans have a recent evolutionary component.
We assessed the extent to which the cognitive phenotypes, College, EduYears, and GCA are affected by genetic variation in regions of the human genome that may have undergone selective sweeps since divergence from the Neanderthals and found nominally significant enrichment with all cognitive traits.
Together, these findings lend support to the hypothesis that higher cognitive traits typical of humans have a component that originated after the separation of the human and Neanderthal lineages, in line with previous theories The fold enrichment and Q-Q plots for the three cognitive phenotypes showed various degrees of deflection in the HD stratum Fig.
The fold enrichment statistics confirmed consistently significant enrichments for College, EduYears, and two independent data sets on GCA. The phenotypes summarized under GCA measure fluid intelligence and capture the shared variance across cognitive traits, irrespective of the tests applied.
GCA is also phenotypically and genetically correlated with educational attainment 37 , The meta-analysis of the stratified LD-score enrichment tests statistics suggests that the enrichments detected here are somewhat specific to cognitive phenotypes.