The population geneticists suggest that the way that the authors set up the analysis might include a bias baked into the screen for alleles associated with the phenotype. A Twitter discussion between several population geneticists has focused on a few details in the analyses of the association between Neandertal-derived variants and cranial shape. The discussion is quite technical but basically boils down to the statistical methods used to identify variants associated with the oblong skull shape. This study is not without some criticism. It is therefore likely that future genome-wide studies in sufficiently large high-powered samples (tens of thousands of people) will reveal additional relevant genes and associated pathways." Moreover, braincase shape depends on a complex interplay between cranial bone growth, facial size, and the tempo and mode of neurodevelopment. "Globularity is a multifactorial trait, involving combined influences of many different loci, and the effects of individual genetic polymorphisms on overall endocranial shape are small. the authors wrote to accompany the study, they noted: Complex traits like cranial shape have very complicated genetic pathways underlying them there is no gene “for” any complex trait. But the authors correctly note that these candidates are just two of what must be many variants involved in influencing the shape of the skull, each with a very small effect. Exactly how these variants might be involved in the development of cranial shape is yet to be determined and would require a lot more work. The two most strongly associated SNPs were involved in the regulation of genes involved in the generation of neurons in one part of the brain (the putamen), and the production of myelin sheaths, the insulators of nerve cells in the cerebellum. They identified 5 genetic variants (single nucleotide polymorphisms, or SNPs) that were significantly associated with a more oblong shaped skull in Europeans. Researchers then tested for associations between the elongated phenotypes and different Neandertal alleles. These are not people that would look Neanderthal-like.” I don’t think you would see it with your naked eye. “It’s a really subtle shift in the overall roundedness. The researchers did find some modern Europeans with slightly more elongated skulls than the average for their population, although this difference is incredibly small, as Philipp Gunz told Nature. Their quantifications of endocranial globularity in modern humans and Neandertals showed that the two groups are quite distinct from each other. These comparisons were used to generate an index of “endocranial globularity” (in other words, how globular brains were). They combined these scans with MRI data from a large number of contemporary peoples from a wide geographic sampling. The research team CT scanned both fossils and contemporary European crania in order to quantify shape differences. The authors reasoned that they might be able to find genes implicated in cranial shape by hunting for an association between Neandertal-derived genetic variants and slightly elongated skulls in Europeans. To do this, they took advantage of the fact that modern humans and Neandertals have interbred, and that some populations (like Europeans) still contain many Neandertal-derived genetic variants. It took some time to get our distinctive head shape, but why?Ī paper published last week in Current Biology by Philipp Gunz and colleagues, “Neandertal Introgression Sheds Light on Modern Human Endocranial Globularity,” attempts to identify genetic variants that might underlie our skull shape. This shape didn’t appear immediately in our species we know that 300,000-year-old modern human fossils from Morocco have elongated crania much like older human species. Modern humans’ crania are globular-shaped, rather than elongated. One of those traits is the unusual shape of our crania (skulls). It is very easy for us to spot differences between our fellow humans-skin color, hair color and texture, body shape, facial features, and so on-but less easy for us to readily see those traits which unite us compared to all other human and hominin groups in the past. They find introgressed Neandertal alleles that associate with reduced endocranial globularity and affect the expression of genes linked to neurogenesis and myelination. In a study published in Current Biology Gunz, Tilot and colleagues combine paleoanthropology, archaic genomics, neuroimaging, and gene expression to study biological foundations of the characteristic modern human endocranial shape. scan of a modern human the cranium was cut open virtually to reveal the inside of the braincase. Left: Computed tomographic (CT) scan of a Neandertal fossil (La Ferrassie 1).
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |