Marine iguanas keep each other warm on Fernandina Island before taking a dip in the Pacific Ocean. Darwin's evolutionary theory is at work here: It's theorized that a long drought on these islands forced the land iguana to the water to find food. Thousands of years later, this adaptation has made the marine iguana look and act different from the land reptile that occupies most of these islands. (Tpn/The Minnesota Star Tribune)

From an editorial in the St. Louis Post-Dispatch:

Charles Darwin wasn't the first to describe what he later called "the struggle to survive," nor was he the first to say that natural selection best explains why animals are so well adapted to their surroundings.

But Darwin was the first to pull together those ideas, along with an impressive amount of evidence, into the theory of evolution. This week, the world celebrates the bicentennial of his birth in Shrewsbury, England, on Feb. 12, 1809. An ocean away, in LaRue County, Ky., Abraham Lincoln was born the same day. Have two more significant historical figures ever shared the same birth date?

Darwin's classic "On the Origin of Species" still is among the most influential books in science — and the foundation of all modern biology. Yet it remains controversial, at least among non-scientists.

We scarcely can imagine polling people today on their views about Newtonian physics or Einstein's theory of relativity. But over the past 20 years, Americans routinely have been surveyed about their acceptance of evolution.

The results are not encouraging. Only about half of Americans say they believe in evolution. That's a lower rate than in most other Western democracies.

Even more distressing was a 2007 Newsweek survey that found just 48 percent of Americans believe evolution is both well-accepted in the scientific community and well-supported by evidence. The reality is that acceptance of evolution among scientists is overwhelming, largely because the evidence is, too.

Darwin's basic idea has been confirmed by more than a century of paleontology and biology — also by discoveries in fields as diverse as geology and genetics that he knew nothing about.

Among them is plate tectonics, the theory of continental drift, which first was proposed in the 1960s. It helps explain why similar animals, such as ostriches and emu, are found in places as distant as Africa and Australia.

Further modern support comes from genetics. Darwin had no idea how changes could be passed on to future generations. Only during the 20th century did real breakthroughs, including discoveries about DNA, provide the explanation.

DNA sequencing completed during the 21st century has demonstrated the close relationship between human and chimpanzee genomes — exactly as predicted by Darwin, who said they descended from a common ancestor.

The controversy persists, as Darwin himself predicted it would, because evolution was the first explanation for the appearance and diversity of life on Earth that did not rely on the divine.

The late evolutionary biologist Stephen Jay Gould argued that Darwin's theory is misunderstood not because of its complexity, but because people don't want to understand it.

Anti-evolutionists believe Darwin's theories imply that the complexity of life, and our role in the world, is the result of accident. Some scientists disagree. Based on what's called "convergent evolution," in which different organisms independently evolve in similar ways, they argue that there are only a limited number of routes for animals and plants to evolve successfully.

Convergent evolution is something that also intrigued Darwin, but one of many details he never resolved.

For all the furor his work engendered, Darwin's towering achievement — and, in the eyes of some, his greatest sin — lay in providing a new framework for understanding life.

We may never have all the answers. But since Darwin, the world around us never has looked quite the same.