More than 140 sign languages are used today， primarily by deaf communities around the world. Like spoken languages， each sign language has its own grammar， vocabulary and other special features.

For example， American Sign Language and British Sign Language are mutually unintelligible. In fact， American Sign Language has more in common with French Sign Language， largely because French educators were instrumental in helping get deaf schools established in the United States during the 19th century.

But while the lineages and development of spoken languages are well-studied， “There havent been a lot of large-scale comparisons of sign languages，” University of Texas at Austin linguist Justin Power says. He and his colleagues aim to address that information gap.

“In order to study the question of sign language evolution， we first assembled a database of manual alphabets from dozens of different sign languages around the world. A manual alphabet is sort of a subsystem within a sign language that is used to represent a written language. So theres a hand shape that corresponds to each letter.”

当今在用的手语超过140种，使用者主要是世界各地的聋哑人。就像口语一样，每种手语也有自己的语法、词汇和其他特征。

例如，使用美国手语的人就无法和使用英国手语的人沟通。事实上，美国手语和法国手语有更多的相似之处，主要是因为19世纪法国教育家对美国聋哑学校的建设起到了重要作用。

盡管人们对口语语系和口语演变进行了深入的研究，“但是目前对手语的大规模对比研究还不多。” 得克萨斯大学奥斯汀分校的语言学家贾斯汀·鲍尔说。贾斯汀和他的同事想要弥补这一信息缺口。

“为了研究手语的演化过程，我们首先收集了全世界几十种不同手语的字母表，组建了一个数据库。手语字母表是手语的一种子系统，用来代表书面语言，也就是说每种手型都会在书面语言中找到对应。”

Powers team chose to study manual alphabets because a record of them exists going back to the late 16th century in Europe. To uncover relationships between the alphabets， the researchers used the same methods that biologists use to trace relationships between different species， based on their DNA.

The methods grouped sign languages in this study into five main European lineages. And those were Austrian origin， British origin， French origin， Spanish origin and Swedish origin.

Power says manual alphabets from Austria， France and Spain could be traced back to one-handed manual alphabets from 16th- and 17th-century Spain. But each of these lineages evolved independently of each other. And the British lineage， which uses a two-handed manual alphabet， eventually made it to Australia， New Zealand and India.

The study also confirmed the French origins of American Sign Language and those of other countries， including Mexico， Brazil and the Netherlands.

Surprisingly， the Austrian manual alphabet influenced sign languages as far away as Russia. But while this lineage has largely died out， remnants of it live on in Icelandic Sign Language today.

The study is in the journal Royal Society Open Science.

Power says future research comparing the vocabularies of different sign languages could provide even more clues about how theyve changed over time.

“Understanding how sign languages evolve would tell us a lot about the way that language， in general， evolves.”

鲍尔的团队选择研究手语字母表，是因为手语字母表的记录可以追溯到16世纪晚期的欧洲。为了找到这些字母表之间的关系，研究人员使用了生物学家同样会用到的方法，生物学家会根据基因追踪不同物种之间的关系。

在这项研究中，研究人员将不同的手语分为五大欧洲语系，分别是奥地利手语、英国手语、法国手语、西班牙手语和瑞典手语。

鲍尔说，奥地利、法国以及西班牙的手语字母表可以追溯到16世纪和17世纪的西班牙单手字母表，但是这些语系均独立演变，互不相干。而英国手语使用的是双手字母表，最终传播到了澳大利亞、新西兰和印度。……