Evolution is the gradual optimization of a population of organisms for its surroundings by means of mutation and natural selection of the most advantageous mutations over the generations.
Organisms make occasional mistakes, called mutations, when copying their DNA. Most of these mutations either are harmless or are deleterious, meaning they give the organism's offspring a disadvantage. But occasionally, mutations are advantageous. The principle of natural selection states that individuals with advantageous mutations are likely to reproduce. Sex allows advantageous mutations in separate individuals to combine and spread throughout the population more quickly.
Microevolution is within one specific taxonomic family. Macroevolution is evolution that leads to the emergence of new families and higher taxa. For the most part, mainstream scientists and religious leaders agree that microevolution happens. However, some faiths disagree with mainstream science on macroevolution, claiming that families arose from intelligent design at creation.
Evolution is distinct from ontogeny, the development of an individual organism, which includes changes in the body's form called metamorphoses. The Pokémon video games and other works of mainstream fiction don't help the matter when they refer to metamorphosis as "evolution", as shown by this incident.
In the twentieth century, some religious organizations became famous for "creationism", a defense of over-literal interpretations of Genesis 1. But by the 2010s, the religious establishment began to accept evolution, first as baraminology (cladistics without a common ancestor) and then as theistic evolution. In October 2014, the Roman Catholic Church's Pope Francis announced that old Earth and theistic evolution better explain observations than "imagining God was a magician, with a magic wand able to do everything." This agrees with what previous popes going back to the 1950s had accepted.
Various indigenous peoples of southeast Asia, sometimes called Sea Gypsies, have adaptations to a seaborne lifestyle. The Moken people can see underwater. One Bajau fisherman is known to hold his breath for up to 5 minutes at a time while hunting 20 meters below the water.
But Sea Gypsy peoples aren't the only ones with adaptations that show human capacity for microevolution. The Sherpa people have adapted to Himalayan high altitude over the course of three millennia with the help of a gene inherited from the ancient Denisovan race. The Kalenjin of Kenya had a different way of adapting to the Great Rift Valley. The short stature of pygmies may be in part an adaptation to conserve vitamin D in the low-UV rainforest environment, or to help them expend less energy ducking under tropical rainforest vegetation. The Laron dwarfs of Ecuador are even shorter, but they're immune to cancer and diabetes.
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