George Frederick Barker (1835-1910) was an American physician and scientist. Born in Charlestown, Massachusetts, he graduated from the Yale Scientific School in 1858. He was successively chemical assistant in Harvard Medical School, professor of Chemistry and Geology in Wheaton College and professor of Natural Science at the Western University of Pennsylvania. He subsequently went to Yale as a professor of Physiological Chemistry and Toxicology, and later was a professor of Physics at the University of Pennsylvania. He served as President of the American Association for the Advancement of Science in 1879, President of the American Chemical Society, Vice-President of the American Philosophical Society, and for several years an associate editor of the American Journal of Science . Modern Aspects of the Life-Question , the essay by George Frederick Barker that we offer today to the attention of modern readers, was the text of the speech delivered by him as outgoing president of the American Association for the Advancement of Science, at the meeting in Boston, August 25, 1880. In it the great American scientist explores the origins of life on Earth and the great mystery of existence.