How weird is it that the two men who may be the most influential people to live and die in the 19th century were born on the very same day?

Abraham Lincoln and Charles Darwin came into the world on Feb. 12, 1809.

One was born in a log cabin in Kentucky to poor parents, the other in a country estate to a wealthy British family.

The two never met. But they both changed the most basic ways that people viewed human existence and helped bring about a new era in the history of human thought.

"If slavery is not wrong, nothing is wrong."Lincoln said that and declared freedom for the South's slaves in the early 1860s, an act for which he is beloved today. But in his own time Lincoln was highly controversial, as was the emancipation of slaves. It may also surprise you that Lincoln's great life was filled with heartbreak and disappointment.

"It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is the most adaptable to change."That was what Darwin realized after a long trip that included a stop in the Galapagos Islands, 600 miles west of South America. His theory that populations of living things evolve over generations through a process called natural selection was published in a famous 1859 book called "On the Origin of Species." Darwin had become popular as a naturalist but was attacked by those who saw evolution as a challenge to the creation story in the Bible.

The revolutions in thought that these men set off — emancipation and evolution — have strong links to life today. The election of Barack Obama as the first black U.S. president completed a circle that started with Lincoln's decision to free the slaves. Today most scientists agree that evolution explains human existence and life's biological complexities. But for some, evolution is still very controversial.