Evolution's birthday

LONDON, Nov. 24 (UPI) -- Charles Darwin's epic work, considered key in establishing the theory of evolution, was published 150 years ago Tuesday.

"On the Origin of Species by Means of Natural Selection," published Nov. 24, 1859, involved Darwin's studies that concluded species change over generations through the process of natural selection. Much of Darwin's field research was compiled while he traveled on the HMS Beagle about 25 years before the book was published.

The idea challenged beliefs that all life on Earth was created in its current form by a Creator and the theory of evolution is still challenged in the 21st century by Creationists and those who posit Intelligent Design -- the idea that while life evolves it does so along a planned path.

Darwin was conflicted about publishing his ideas because he knew they would shake the foundations of 19th-century thought and deeply held religious beliefs. The debate on natural selection and the development of life on Earth remains at the center of many arguments in the 21st century.