Living things inherit characteristics from the generations that have gone before, but each individual is slightly different. Over many generations, the differences that are more successful survive, so that the species gradually adapts. In time, these changes, called evolution, can lead to major adaptations and even new species. All living things have evolved from the simple organisms that began to grow in the Earth’s waters. Many of these, such as the dinosaurs, have since become extinct, although they may have lived successfully on Earth for millions of years.
The theory of evolution by natural selection, first formulated in Darwin’s book “On the Origin of Species” in 1859, is the process by which organisms change over time as a result of changes in heritable physical or behavioral traits. Changes that allow an organism to better adapt to its environment will help it survive and have more offspring.
Evolution by natural selection is one of the best substantiated theories in the history of science, supported by evidence from a wide variety of scientific disciplines, including paleontology, geology, genetics and developmental biology.
The theory has two main points, said Brian Richmond, curator of human origins at the American Museum of Natural History in New York City. “All life on Earth is connected and related to each other,” and this diversity of life is a product of “modifications of populations by natural selection, where some traits were favored in and environment over others,” he said.
More simply put, the theory can be described as “descent with modification,” said Briana Pobiner, an anthropologist and educator at the Smithsonian Institution National Museum of Natural History in Washington, D.C., who specializes in the study of human origins.
The theory is sometimes described as “survival of the fittest,” but that can be misleading, Pobiner said. Here, “fitness” refers not to an organism’s strength or athletic ability, but rather the ability to survive and reproduce.
For example, a study on human evolution on 1,900 students, published online in the journal Personality and Individual Differences in October 2017 found that many people may have trouble finding a mate because of rapidly changing social technological advances that are evolving faster than humans. “Nearly 1 in 2 individuals faces considerable difficulties in the domain of mating,” said lead study author Menelaos Apostolou, an associate professor of social sciences at the University of Nicosia in Cyprus. “In most cases, these difficulties are not due to something wrong or broken, but due to people living in an environment which is very different from the environment they evolved to function in.”
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