"I am sharpening up my claws and beak in readiness," these are the words of Thomas H. Huxley in a letter to Charles Darwin regarding the Origin of Species. He always warned Darwin that there would be mischief from anti-evolutionists, and that he himself was preparing to annihilate the creationist critics. He was one of the first adherents to Darwin's theory of evolution by natural selection, and did more than anyone else to advance its acceptance among scientists and the public alike. As is evident from the quote above, Huxley was a passionate defender of Darwin's theory, so passionate that he has been called "Darwin's Bulldog". But Huxley was not only the bulldog for Darwin's theory, but was a great biologist in his own right. Nor did he slavishly and uncritically swallow Darwin's theory; he criticized several aspects of it, pointing out a number of problems. Although Darwin created the Theory of evolution, Huxley would do almost anything to defend it. .
Charles Darwin was born in Shrewsbury, England, on February 12, 1809, sharing the same birthday with Abraham Lincoln. As a young boy he developed an interest in natural history but started his advanced schooling at Edinburgh in medicine, a subject he soon learned to detest. Later at Cambridge, where he went to prepare for a career in the clergy, he became acquainted with a botany professor John Henslow. Henslow encouraged Darwin to take an extended sea voyage and exploration of the world outside of England. Darwin took advantage of the opportunity and became the expedition naturalist and gentlemen's companion to Captain Robert FitzRoy, on the HMS Beagle. The intended 3-year voyage stretched to 5 years, and Darwin had wonderful experiences as he circumnavigated the world. Upon his return to England he arranged his notes and read voraciously in all fields of science, filling notebook after notebook with his insights. He expanded these ideas into a 35-page paper and then into a longer 230-page paper.