Today marks the 200th anniversary of the birth of naturalist Charles Darwin, and the 150th anniversary of the publication of his book On the Origin of Species. Darwin did not create the theory of evolution, which dates back to the Greeks; he only postulated the mechanism by which it occurred, natural selection.
Despite the efforts of certain people to discredit evolutionary theory, because of a vested interest in Bronze Age superstitions that cannot be reconciled with observable fact, our understanding of evolution forms the cornerstone not only of modern biology, but resonates throughout all of the natural sciences, from chemistry to archaeology to anthropology to medicine.
If evolution weren't true, none of the modern medications or antibiotics we have would work. But they do, because it is.
There was a lot that Darwin didn't know about -- he had no knowledge of what we today call genetics, for example. Although DNA would be discovered during his lifetime, its implications in relationship to natural selection would not be understood until the mid-20th century. With all the advancements in knowledge we have made in the last century and a half, Darwin would likely find any of the current work being done in the field of evolutionary biology completely mystifying.
But through 150 years of science, evolution by means of natural selection has been proven, and strengthened, with every new discovery. There are certainly conceivable discoveries that could be made that would render the theory invalid, or at least inadequate to explain them; but such discoveries have, to date, never been made. Anyone who tells you that evolution is a "theory in crisis" is either ignorant of the facts, or lying about them.
Ars Technica has an article about appreciating evolution. I'm sure you will find many more out there to enjoy and learn from.
Today, by the way, also happens to be the actual 200th anniversary of Abraham Lincoln's birthday. So props to him too, though the official birthday celebration has been paired with the celebration of Washington's birthday and gets everyone not working in post-production a day off on Monday.