Literature Review: Human Evolution

by Carl Strang

Human. Photo by Linda Padera.

Human. Photo by Linda Padera.

Kimbel, William H., et al. 2014. Ardipithecus ramidus and the evolution of the human cranial base. Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1322639111  From a ScienceDaily article. The base of this skull of the 3.4-million-year-old species Ardipithecus ramidus places it in the Australopithecus-human line and separates it from chimpanzees and other apes. The shape features may reflect a change to a more upright posture, or the early reorganization of the brain. Earlier studies had indicated that Ardipithecus was arboreal but also could walk upright on the ground.

Ashton, N., et al. 2014. Hominin footprints from Early Pleistocene deposits at Happisburgh, UK. PLoS ONE 9(2): e88329. doi:10.1371/journal.pone.0088329 They describe footprints of hominins estimated to be 850,000 years old, in sediments of an age where flint tools have been found, and establishing the earliest evidence of hominins outside of Africa. A combination of pollen analysis and stratigraphy (e.g., the footprints are beneath glacial sediments) established the age.

Vernot, Benjamin, and Joshua M. Akey. 2014. Resurrecting surviving Neandertal lineages from modern human genomes. Science 343:1017-1021. Gibbons, Ann. 2014. Neandertals and moderns made imperfect mates. Science 343:471-472. The Gibbons article is a news review describing Vernot and Akey’s study, which showed that though Neandertals and modern humans interbred, there were costs to the hybridization. Only a small amount of Neandertal genetic material has persisted in Europeans and East Asians as a result, mainly genes connected with keratin function, and so affecting skin color, waterproofing, and resistance to cold, helping modern humans to survive in more northern latitudes. They looked at whole genomes of several hundred European and Asian people, and found that collectively they preserve about 20% of the Neanderthal genome (each individual has only 1-3%).

Huerta-Sánchez, Emilia, et al. 2014. Altitude adaptation in Tibetans caused by introgression of Denisovan-like DNA. Nature, DOI: 10.1038/nature13408 From a ScienceDaily article. They looked at the genetics of these high altitude dwellers, and found that the main adaptation that allows them to live in low oxygen without heart problems comes from a gene their ancestors got through the Denisovans. The individuals who first moved into the area had some in their number descended from a modern human-Denisovan cross, and those people had a selective advantage in that environment.

Rasmussen, Morten, et al. 2014. The genome of a Late Pleistocene human from a Clovis burial site in western Montana. Nature 506 (7487): 225. DOI: 10.1038/nature13025 They worked up the genome of the only skeleton ever found in association with Clovis tools, that of a boy less than 2 years old found in a burial. His family and relatives are found to be ancestral to all Native Americans, and connected to Asian ancestors. The boy shares about 1/3 of his genes with the Baikal boy whose genome was sequenced in 2013, with the rest coming from east Asians, that blend happening before emigrating across the Bering Sea land bridge. The Clovis culture developed after the people were established in the New World, well before the 12,600-year age of the newly sequenced genome.

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