In addition to the origin of species, Charles Darwin was also interested in the origin of language. Darwin noted how many animals communicate with each other through the use and imitation of certain noises. He noticed that the many animals, particularly mammals, make similar noises to each other, even to humans, to communicate the same ideas. Darwin also observed the onomatopoetic nature of many basic words. Words like, boom, growl, and squeak, all sound like what they describe. Darwin noted this to be a common theme in many languages. He posited that early human speech likely began as imitations of natural sounds. Even some animals, like certain monkeys and birds, appear to mimic natural sounds.
During the nineteenth century, there were many who believed that language was a divinely given ability, unique to humans. In his 1871 work Descent of Man, Darwin acknowledged that human language is distinctly different from how animals communicate. Yet he drew parallels between people and animals. Darwin noted how human children learn language through mimicking the sounds of adults, much like how a baby bird does with its parents in the nest. Darwin supposed that early humans, or a recent ancestor of humans, might have developed basic song in order to court a sexual partner and may have mimicked the sounds of predators in order to communicate danger to others. As language and communication evolved, so too would reasoning and thinking abilities. As a result, the increased use of vocal communication would have gone hand in hand with increased intelligence.