Two hundred years ago, on February 12, 1809, a pair of cosmic twins entered the universe. Abraham Lincoln was born in a log cabin in Kentucky. Across the Atlantic, Charles Darwin was born on an English estate. When they left this earth they made an everlasting mark on the principles of democracy and human evolution. Writer Adam Gopnik gives meaning and significance to this enduring convergence in his new book Angels and Ages: A Short Book About Darwin, Lincoln, and Modern Life. He joins us now for a celebration of the 200th birthday of two amazing men.

For more on these two men, read the New York Times science article, Crunching the Data for the Tree of Life, browse Darwin's complete works online, buy the two books that will share this year's Lincoln prize for scholarship on the 16th president, and peruse William Safire's review of Lincoln literature.