Here is an excerpt from Wikipedia:
"Darwin Day is the anniversary of the birthday of Charles Darwin on February 12, 1809.
Darwin provided the first coherent theory of evolution by means of natural selection. His theory has had far-reaching implications in almost all disciplines and has rocked the very foundation of our knowledge base. Human civilization has been deeply affected by Darwin's work, with over 200 years of evidence supporting his initial findings with modification and refinement continuing to this day. For his contributions to humanity and his commitment to scientific methodology, Charles Robert Darwin is celebrated globally. The date that is recognized by most is that of February 12th, the date of his birth."
Darwin's contribution to human knowledge is simply tremendous, perhaps only Einstein has had greater influence, but it's debatable. All biology & medical science today rests on the foundation Darwin laid down 150 years ago in "Origin of Species."
Evolution is the best scientific theory we have today, fully proven thousands of times of the past 150 years. It's so good a competing theory doesn't even exist.