This basic concern with evolutionary theory has helped drive the decadeslong opposition to teaching it in public schools. Even over the last 15 years, educators, scientists, parents, religious leaders and others in more than a dozen states have engaged in public battles in school boards, legislatures and courts over how school curricula should handle evolution. The issue was even discussed and debated during the runups to the and presidential elections.
This battle has ebbed in recent years, but it has not completely died out. Outside the classroom, much of the opposition to evolution has involved its broader social implications and the belief that it can be understood in ways that are socially and politically dangerous. For instance, some social conservatives charge that evolutionary theory serves to strengthen broader arguments that justify practices they vehemently oppose, such as abortion and euthanasia.
Evolutionary theory also plays a role in arguments in favor of transhumanism and other efforts to enhance human abilities and extend the human lifespan. Still other evolution opponents say that well-known advocates for atheism, such as Richard Dawkins, view evolutionary theory not just as proof of the folly of religious faith, but also as a justification for various types of discrimination against religion and religious people.
A look back at American history shows that, in many ways, questions about evolution have long served as proxies in larger debates about religious, ethical and social norms. From efforts on the part of some churches in the 19th and early 20th centuries to advance a more liberal form of Christianity, to the more recent push and pull over the roles of religion and science in the public square, attitudes toward evolution have often been used as a fulcrum by one side or the other to try to advance their cause.
In formulating his theory of evolution through natural selection, Charles Darwin did not set out to create a public controversy. In fact, his concerns over how his ideas would be received by the broader public led him to wait more than 20 years to publicize them. He might never have done so if another British naturalist, Alfred Russel Wallace, had not in independently come up with a very similar theory. At that point, Darwin, who had already shared his conclusions with a small number of fellow scientists, finally revealed his long-held ideas about evolution and natural selection to a wider audience.
Darwin built his theory on four basic premises. First, he argued, each animal is not an exact replica of its parents, but is different in subtle ways. Second, he said, although these differences in each generation are random, some of them convey distinct advantages to an animal, giving it a much greater chance to survive and breed.
Over time, this beneficial variation spreads to the rest of the species, because those with the advantage are more likely than those without it to stay alive and reproduce. And, finally, over longer periods of time, cumulative changes produce new species, all of which share a common ancestor. The book became an instant bestseller and, as Darwin had feared, set off a firestorm of controversy in his native Britain.
While many scientists defended Darwin, religious leaders and others immediately rejected his theory, not only because it directly contradicted the creation story in the biblical book of Genesis, but also because — on a broader level — it implied that life had developed due to natural processes rather than as the creation of a loving God.
Moody, began to inveigh against Darwinism as a threat to biblical truth and public morality. From the s to the s, the major American Protestant denominations gradually split into two camps: modernist, or theologically liberal Protestantism what would become mainline Protestantism ; and evangelical, or otherwise theologically conservative, Protestantism. This schism owed to numerous cultural and intellectual developments of the era, including, but not limited to, the advent of new scientific thinking.
Theologians and others also grappled with new questions about the historical accuracy of biblical accounts, as well as a host of provocative and controversial new ideas from such thinkers as Karl Marx and Sigmund Freud about both the individual and society. Modernist Protestants sought to integrate these new theories and ideas, including evolution, into their religious doctrine, while more conservative Protestants resisted them.
The issue became a mainstay for Protestant evangelists, including Billy Sunday, the most popular preacher of this era.
But it was William Jennings Bryan, a man of politics, not the cloth, who ultimately became the leader of a full-fledged national crusade against evolution. Alfred Russel Wallace noted the similarities and differences between nearby species and those separated by natural boundaries in the Amazon and Indonesia.
Independently they came to the same conclusion: over generations, natural selection of inherited traits could give rise to new species. Use the resources below to teach the theory of evolution in your classroom.
When most of us think about natural selection, we attribute that theory to naturalist Charles Darwin. However, what most people do not know is that another scientist, Alfred Wallace, a naturalist, a geographer, and a socialist, also deserves some credit for the theory. Evolution is the process by which species adapt over time in response to their changing environment. Use these ideas to teach about the water cycle in your classroom. Evolutionary adaptation, or simply adaptation, is the adjustment of organisms to their environment in order to improve their chances at survival in that environment.
Join our community of educators and receive the latest information on National Geographic's resources for you and your students. Skip to content. Image Young Charles Darwin Charles Darwin is more famous than his contemporary Alfred Russel Wallace who also developed the theory of evolution by natural selection. Photograph by James L.
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Interactives Any interactives on this page can only be played while you are visiting our website. Related Resources. View Collection. Instead of looking at bears, he should have been looking at cows and hippopotamuses. The story of the origin of whales is one of evolution's most fascinating tales and one of the best examples scientists have of natural selection.
To understand the origin of whales, you need a basic understanding of how natural selection works. Natural selection can alter a species in small ways, causing a population to change color or size over the course of several generations. When this process happens over a relatively short period of time and in a species or small group of organisms, scientists call it "microevolution. But when given enough time and accumulated changes, natural selection can create entirely new species, a process known as "macroevolution.
Take the example of whales: By using evolution as a guide and understanding how natural selection works, biologists knew that the transition of early whales from land to water occurred in a series of predictable steps. The evolution of the blowhole, for example, might have started with random genetic changes that resulted in at least one whale having its nostrils farther back on its head. The whales with this adaptation would have been better suited to a marine lifestyle, since they would not have had to completely surface to breathe.
Such individuals were more successful and had more offspring. In later generations, more genetic changes occurred, moving the nose farther back on the head. Other body parts of early whales also changed. Front legs became flippers. Back legs disappeared. Their bodies became more streamlined, and they developed tail flukes to better propel themselves through water. Darwin also described a form of natural selection that depends on an organism's success at attracting a mate — a process known as sexual selection.
The colorful plumage of peacocks and the antlers of male deer are both examples of traits that evolved under this type of selection. But Darwin wasn't the first or only scientist to develop a theory of evolution.
Around the same time as Darwin, British biologist Alfred Russel Wallace independently came up with the theory of evolution by natural selection, while French biologist Jean-Baptiste Lamarck proposed that an organism could pass on traits to its offspring, though he was wrong about some of the details.
Like Darwin, Lamarck believed that organisms adapted to their environments and passed on those adaptations. He thought organisms did this by changing their behavior and, therefore, their bodies — like an athlete working out and getting buff — and that those changes were passed on to offspring. For example, Lamarck thought that giraffes originally had shorter necks but that, as trees around them grew taller, they stretched their necks to reach the tasty leaves and their offspring gradually evolved longer and longer necks.
Lamarck also believed that life was somehow driven to evolve through the generations from simple to more complex forms, according to Understanding Evolution , an educational resource from the University of California Museum of Paleontology. Though Darwin wasn't sure of the mechanism by which traits were passed on, he did not believe that evolution necessarily moved toward greater complexity, according to Understanding Evolution; rather, he believed that complexity arose through natural selection.
A Darwinian view of giraffe evolution, according to Quanta , would be that giraffes had natural variation in their neck lengths, and that those with longer necks were better able to survive and reproduce in environments full of tall trees, so that subsequent generations had more and more long-necked giraffes. The main difference between the Lamarckian and Darwinian ideas of giraffe evolution is that there's nothing in theDarwinian explanation about giraffes stretching their necks and passing on an acquired characteristic.
Darwin didn't know anything about genetics, Pobiner said. That came later, with the discovery of how genes encode different biological or behavioral traits, and how genes are passed down from parents to offspring. The incorporation of genetics into Darwin's theory is known as "modern evolutionary synthesis.
The physical and behavioral changes that make natural selection possible happen at the level of DNA and genes within the gametes, the sperm or egg cells through which parents pass on genetic material to their offspring. Such changes are called mutations.
Mutations can be caused by random errors in DNA replication or repair, or by chemical or radiation damage. Usually, mutations are either harmful or neutral, but in rare instances, a mutation might prove beneficial to the organism.
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