Thursday was the 200th anniversary of the birth of Charles Darwin, the British naturalist whose theory of evolution revolutionized the telling of human history.
Darwin is most famous for his book, On the Origin of Species, which asserts that humans evolved over millions of years from apes.
The theory took shape on a journey through the Pacific islands off Ecuador, where Darwin collected thousands of specimens of rocks, fossils, insects and birds.
From his observations, he developed the idea that all species of life have evolved over time from one or a few common ancestors through the process of natural selection.
Although the theory originally shook the belief that Earth was created by a higher power, it is now widely accepted.
Still, skeptics remain. A public opinion poll released in the United States this week by the Gallup organization reports that only 39 percent of Americans believe in evolution.
Some information for this report was provided by AFP, AP and Reuters