A new study by linguists and biologists from UT and the Max Planck Institute for the Science of Human History tracked the evolution of sign languages around the world over the past few centuries.  

The team tracked the evolution using phylogenetics, the study of the ancestral relatedness of groups of organisms. The study, published in the journal Royal Society Open Science last Wednesday, grouped most sign languages into five main European sign language lineages. 

Linguistics graduate student Justin Power said scholars understand more about how spoken languages evolve than sign language since spoken languages receive more scientific attention.

“Much less is known about how sign languages change over time,” Power said.

Power said few studies have used language data to understand how sign languages relate to one another in terms of evolution. Power said the team used phylogenetic network methods to compare dozens of sign languages and identified five main European sign language lineages that dispersed to other parts of the world beginning in the late 18th century. 

“The study sheds light on the origins and evolution of European sign languages,” Power said. 

Power said this study began by building an annotated database of 40 contemporary and 36 historical manual alphabets, which are a set of handshapes that represent a written alphabet. 

“The database helped us track the evolution of sign languages over the past few centuries, providing a clearer picture about the roots of the contemporary diversity of the sign languages in the study,” Power said. 

Based on the results, they grouped the sign languages in the study into five main European lineages, Power said. 

“In this study, we were looking mainly at sign languages that evolved in Europe and spread to other parts of the world,” Power said. “Of course, there are many other sign languages in the world that we did not include in the study for practical reasons.”

Linguistics associate professor David Quinto-Pozos said this research allows people to consider how language change happens.

“We do have some studies on the evolution of American Sign Language, and it’s probably the language we have studied the most,” Quinto-Pozos said. “(The phylogenetic approach) is unique in a couple ways because it’s a newer way of looking at language change, but also it’s looking at (signed languages) through the lens of the finger-spelling system.”

Quinto-Pozos said he tries to say “signed languages,” instead of sign language because multiple sign languages exist. 

“When I write about signed languages in my own work, every time I refer to American Sign Language, I try to be specific about it,” Quinto-Pozos said. “This is because it helps people alleviate the myth or misconception that there is one sign language.”  

Johann-Mattis List, a Max Planck Institute for the Science of Human History researcher, said he hopes the study inspires young scholars to study their workflows, learn from them and make them better.

“(The research) is challenging and fascinating,” List said. “It was a very pleasant collaboration experience for me showing how important it is to work across disciplines.”