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.
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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 controver- sial.
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.
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 comple- ted 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 under- stand it.