Final answer:
The statement is false; historical linguists study language evolution and change over time, which includes more than just variations within one group. They also consider broader influences like migration and political events, and how dialects reflect cultural diversity.
Step-by-step explanation:
The statement given in the question that historical linguists focus on linguistic variation within one group of speakers, such as regional dialects, is false. Historical linguists study the evolution and patterns of change in languages over time, which includes but is not limited to variations within a single group of speakers. They also consider influences like migration, political and historical events, and interaction among different languages and dialects.
A dialect is a form of language specific to a particular region or social group. Examples include regional dialects like Southern English or social dialects like African American Vernacular English (AAVE). Over time, dialects may evolve significantly enough that they become identified as distinct languages, often influenced by political and sociocultural factors.
Research on dialects does not solely focus on variation within one group but involves understanding the linguistic diversity and relativity that reflects different historical, environmental, and sociocultural conditions. English dialects contribute to an understanding of the wide array of language practices, often embedded in distinct geographical regions or social categories.