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Natural selection is the differential survival and reproduction of individuals due to differences in phenotype.It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations.
Human accelerated regions are areas of the genome that differ between humans and chimpanzees to a greater extent than can be explained by genetic drift over the time since the two species shared a common ancestor. These regions show signs of being subject to natural selection, leading to the evolution of distinctly human traits.
Recent human evolution refers to evolutionary adaptation, sexual and natural selection, and genetic drift within Homo sapiens populations, since their separation and dispersal in the Middle Paleolithic about 50,000 years ago. Contrary to popular belief, not only are humans still evolving, their evolution since the dawn of agriculture is faster ...
Anatomically modern humans appear in Africa. [103] [104] [105] Around 50 ka they start colonising the other continents, replacing Neanderthals in Europe and other hominins in Asia. 70 ka Genetic bottleneck in humans (Toba catastrophe theory). 40 ka Last giant monitor lizards (Varanus priscus) die out. 35-25 ka Extinction of Neanderthals.
Anatomically modern human populations continue to evolve, as they are affected by both natural selection and genetic drift. Although selection pressure on some traits, such as resistance to smallpox, has decreased in the modern age, humans are still undergoing natural selection for many other traits. Some of these are due to specific ...
Sexual selection is strong when the factor of environmental selection is also introduced. Environmental selection may support a smaller chick size if those chicks were born in an area that allowed them to grow to a larger size, even though under normal conditions they would not be able to reach this optimal size for migration.
There is a notable difference between the opinion of scientists and that of the general public in the United States. A 2009 poll by Pew Research Center found that "Nearly all scientists (97%) say humans and other living things have evolved over time – 87% say evolution is due to natural processes, such as natural selection. The dominant ...
Anole lizards, with populations on isolated islands, are one of the best examples of both adaptive radiation and convergent evolution. Anoles on a given island evolve into multiple body types and ecological preferences, and the same set of body types appears in unrelated species across distant islands. [93]