In all cultures, humans talk and sing with each other. We have created an amazing variety of musical languages and structures around the world. And yet, within this diversity, some fundamental sequence patterns repeat. These are often called “universal” patterns in human vocalization. Our new research, published this week in Science, reveals that many of these acoustic patterns in human song and speech are also shared with bird song. The study compared the songs of 367 bird species with examples of songs and speech from 52 human languages. How we collected the data As researchers in animal behavior, neuroscience, and music, we (Logan and Jon) spent 10 years documenting the prevalence of universal human acoustic patterns in the songs of zebra finches. A zebra finch. (Unsplash/Angelo Casto) When Kendra joined our lab during her PhD, she proposed that we investigate whether these patterns are also shared among other bird species. To investigate this, we needed a large number of recordings of bird songs. Fortunately, many people around the world are fascinated by bird sounds and upload their recordings to public repositories. We collected and manually annotated individual syllables in the songs of more than 360 bird species, generating more than 70,000 bird song syllables for analysis. We then compared them to data sets of human speech and singing from a variety of languages and cultures from around the world. Fortunately, some of these data sets contain annotated recordings of the same individual producing both speech and song, which was perfect for our comparisons with bird vocalizations. Both humans and birds tend to end their sentences with a longer syllable. (Unsplash) Regular and predictable rhythms Overall, we find numerous similarities in the acoustic patterns of bird songs and human vocalizations. For example, both humans and birds tend to end their sentences with longer syllables. They also organize their syllables in a way that minimizes pitch changes between adjacent syllables. And they tend to produce their songs with regular, predictable rhythms. In some cases, birdsong seemed more similar to human singing than human speech. In other cases, we found that birds tended to have songs that were more like human speech than human song. Unrelated to vocal learning We designed this study to ask an important question: does vocal learning ability shape sequence patterns? Humans learn the structure of their vocalizations from others, especially as they grow. It turns out that many birds also learn their vocalizations as they grow. We observed two separate groups of these vocally learning birds: songbirds (oscines) and hummingbirds. We compared them to two closely related groups of birds that do not learn vocally: suboscines and nightjars. Because humans, songbirds, and hummingbirds learn vocally, we think some patterns may be similar within these species and distinct from those of suboscines and nightjars. Surprisingly, we found very little evidence of this. The degree of variation between bird species did not appear to be related to vocal learning. Yellow-rumped warbler, an oscine songbird. (Unsplash) How humans and birds produce sounds What then could drive the similarities in sequence patterns between so many species? We’ll need more studies to determine the answer, but we hypothesize that similarities in the way humans and birds produce sounds could shape some vocal sequence patterns. For example, the shared need to coordinate breathing with vocal musculature could contribute to shared acoustic patterns between birds and humans. Specifically, the precise movement of the muscles that control the vocal tract is synchronized with the airflow of the lungs in all birds and humans. If this is true, these patterns may be found in many other species. Did birds teach us to sing? Did birdsong influence the evolution of human sound? (Unsplash) Songbirds first evolved about 50 million years ago, long before the first lines of humans separated from the other great apes. This means that birds have decorated our soundscapes throughout human evolution. Bird songs have inspired music throughout time and cultures. Could these natural sounds have influenced early humans when they began experimenting with creating sounds and discovered the pleasure of music in their ears? These are some of the big ideas we’re excited to explore in future studies.
