To survive, living things adapt to their surroundings. Occasionally a genetic variation gives one member of a species an edge. That individual passes the beneficial gene on to its descendents. More individuals with the new trait survive and pass it on to their descendents. If many beneficial traits arise over time, a new species—better equipped to meet the challenges of its environment—evolves.

Like gravity and plate tectonics, evolution is a scientific theory. In science, a theory is the most logical explanation for how a natural phenomenon works. It is well tested and supported by abundant evidence. It means quite the opposite from our informal use of the word theory, which implies an untested opinion or guess. As a scientific theory, evolution enables scientists to make predictions and drives investigations that lead to new kinds of observable evidence. 

Evolution doesn’t happen all at once, especially in complex organisms such as human beings. Modern humans are the product of evolutionary processes that go back more than 3.5 billion years, to the beginnings of life on Earth. We became human gradually, evolving new physical traits and behaviors on top of those inherited from earlier primates, mammals, vertebrates, and the very oldest living organisms.

Humans and monkeys are both primates. But humans are not descended from monkeys or any other primate living today. We do share a common ape ancestor with chimpanzees. It lived between 8 and 6 million years ago. But humans and chimpanzees evolved differently from that same ancestor. All apes and monkeys share a more distant relative, which lived about 25 million years ago.

Human evolution, like evolution in other species, did not proceed in a straight line. Instead, a diversity of species diverged from common ancestors, like branches on a bush. Our species, Homo sapiens, is the only survivor. But there were many times in the past when several early human species lived at the same time.

Evolution is the cornerstone of modern biology. There is no scientific controversy about whether evolution occurred or whether it explains the history of life on Earth. As in all fields of science, knowledge about evolution continues to increase through research and serious debate. For example, scientists continue to investigate the details of how evolution occurred and to refine exactly what happened at different times.

Scientists have developed more than a dozen methods for determining the age of fossils, human artifacts, and the sediments in which such evidence is found. These methods can date objects millions of years old. What’s more, the methods can be tested against one another to provide a highly reliable record of the past. Read more about dating methods here.

Among the major sources of evidence are sediment cores from the ocean bottom. They preserve the fossils of tiny organisms called foraminifera. By measuring oxygen in the skeletons of these organisms, scientists can calculate fluctuations in temperature and moisture over millions of years. Some of the most dramatic climate fluctuations in all of Earth’s history occurred during the period of human evolution.

A lot! Since Darwin died in 1882, findings from many fields have confirmed and greatly expanded on his ideas. We’ve learned that Earth is old enough for all known species to have evolved. We’ve discovered DNA, which confirms that all organisms are related to one another. And we’ve uncovered millions of fossils that provide evidence of how one life form evolved into another over time.

Some members of both religious and scientific communities consider evolution to be opposed to religion. But others see no conflict between religion as a matter of faith and evolution as a matter of science. Still others see a much stronger and constructive relationship between religious perspectives and evolution. Many religious leaders and organizations have stated that evolution is the best explanation for the wondrous variety of life on Earth.

Many scientists are people of faith who see opportunities for respectful dialogue about the relationship between religion and science. Some people consider science and faith as two separate areas of human understanding that enrich their lives in different ways. This Museum encourages visitors to explore new scientific findings and decide how these findings complement their ideas about the natural world.

In science, gaps in knowledge are the driving force behind the ongoing study of the natural world and how it arose. The science of human origins is a vibrant field in which new discoveries continually add to our understanding of how we became human. You can learn about some of the most recent findings in this exhibit.

Societies worldwide express their beliefs through a wide diversity of stories about how humans came into being. These stories reflect the universal curiosity people have about our origins. For millennia, they have played a vital role in helping people develop an identity and an understanding of themselves as well as of their community. This exhibit presents research and findings based on scientific methods that are distinct from these stories.