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Bird songs and human speech have a common vocal genetic origin

The dawn chorus of robins, the haunting call of a loon, the melodious trill of a nightingale — birdsong has captivated humanity for millennia. Yet, the biological mechanisms behind these mesmerizing vocals of birds have remained largely mysterious.

Now, a research from the University of Texas at Austin is shedding light on the bird vocal organ, the syrinx, and its surprising evolutionary link to the human larynx.

Modern imaging of fossilized syrinx

The story begins in 2013 when paleontologist Julia Clarke unearthed a fossilized syrinx, the oldest ever discovered, in Antarctica. This serendipitous find sparked a quest to understand the evolution and diversity of this unique vocal organ.

Clarke and her team embarked on a decade-long journey, developing innovative methods for dissecting, preserving, and CT-scanning syrinxes from various bird species.

“We had this new three-dimensional structure, but we had nothing to compare it to,” Clarke said, describing the challenge of comparing the fossil syrinx to modern counterparts. “So, we started generating data that did not previously exist on syrinx structure across many different groups of birds.”

Ostriches, hummingbirds, and their behavior

The research team’s efforts have yielded fascinating insights into the anatomy and function of the syrinx in birds as diverse as the mighty ostrich and the tiny hummingbird.

While one might expect significant anatomical differences between the vocal organs of these avian extremes, the research reveals a surprising twist — behavior plays a crucial role in the sounds birds produce.

In ostriches, for instance, adult males and females have remarkably similar syrinx anatomies. However, males exhibit a broader vocal repertoire, often associated with displays of aggression.

“They were quite prolific hissers,” quipped Michael Chiappone, lead author of the ostrich study, describing the vocalizations of female ostriches during a visit to a Texas ostrich farm.

Similarly, the study of hummingbird syrinxes unveiled a surprising similarity in vocal fold structure with their close relatives, swifts and nightjars.

This finding suggests that this shared anatomy may have paved the way for the evolution of vocal learning in hummingbirds, allowing them to acquire complex songs from each other.

Perhaps the most remarkable discovery of this research is the deep homology between the avian syrinx and the mammalian larynx.

Scientists have long known that these organs develop from different embryological layers, but a collaborative study with developmental biologist Clifford Tabin revealed a shared genetic blueprint.

“They form under the influence of the same genetic pathways, ultimately giving the vocal tissue similar cellular structure and vibratory properties in birds and mammals,” Tabin explained.

This unexpected genetic connection suggests that the ability to produce vocalizations evolved from a common ancestral origin, deepening our understanding of the interconnectedness of life.

Bird vocal origin and the syrinx

The research team explored the genetic origins of the syrinx, analyzing its development in 14 bird species. Their findings suggest that the common ancestor of modern birds likely had a syrinx with two sound sources.

This configuration enabled the production of two distinct sounds simultaneously. This dual-voice capability is still present in songbirds today. The presence of this trait hints at the rich and complex vocalizations of ancient avian ancestors.

The study provides insights into how the syrinx evolved and its role in bird communication, shedding light on the sophisticated nature of bird vocalizations.

Mysteries of dinosaur sounds

While the discovery of a shared genetic blueprint between the syrinx and larynx is a major leap forward, many questions remain unanswered.

The precise timing of the syrinx’s evolution and whether non-avian dinosaurs possessed this vocal organ are still unknown.

“We can’t start talking about sound production in dinosaurs until we truly understand the system in living species,” explains Clarke.

The research team is committed to continuing their exploration of vocalization in birds and other reptiles, hoping to unravel the mysteries of how dinosaurs communicated millions of years ago.

Melody of syrinx evolution

The UT Austin research on the syrinx is a testament to the power of interdisciplinary collaboration and innovative research methods.

By bridging paleontology, developmental biology, and physiology, scientists are piecing together the evolutionary puzzle of vocalization, revealing the surprising genetic symphony that connects bird’s song to human speech.

“This is as big as the flippers-to-limbs transition… the syrinx is not a modified organ with a new function but a completely new one with an ancient and common function,” notes Clarke.

This research not only deepens our understanding of birdsong but also highlights the remarkable interconnectedness of life on Earth.

The study is published in the journal Zoological Journal of the Linnean Society.


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