Huxley 's public lectures grew into his most famous work Man 's place in Nature ( 1863 ) . There he deals with the evolution of man , before Charles Darwin published his Descent of Man in 1871 . Other lectures grew into Huxley 's most famous work Evidence as to Man 's place in Nature ( 1863 ) where he addressed the key issues long before Charles Darwin published his Descent of Man in 1871 .