“Perhaps the most striking aspect of this entire subject is that there are nonhuman primates so close to the edge of language, so willing to learn, so entirely competent in its use and inventive in its application once the language is taught. But this raises a curious question: Why are they all on the edge? Why are there no nonhuman primates with an existing complex gestural language? One possible answer, it seems to me, is that humans have systematically exterminated those other primates who displayed signs of intelligence.”

American astronomer, planetary scientist and science communicator

Carl Edward Sagan was an American astronomer, planetary scientist and science communicator. He worked at Harvard as an assistant professor before moving to Cornell University, where he became the David Duncan Professor of Astronomy and Space Sciences and directed the Laboratory for Planetary Studies. Sagan took an active role in the Mariner, Viking and Voyager programs. He also wrote more than 600 scientific papers and articles, along with several popular science books, beginning with The Cosmic Connection. His The Dragons of Eden won the Pulitzer Prize for General Nonfiction.