Historical linguistics is about how and why language changes over time. Comparative linguistics, in the relevant sense, is the study of linguistic relatedness, that is to say, of genetic or ancestral connections and related matters of subgrouping extending to the reconstruction of unattested ancestral languages or proto-languages. This area is often regarded as the oldest branch of modern scientific linguistics, and it is one of the most active areas today. The powerful case put forward by the neogrammarians for the regularity of sound change allowed comparison of linguistic phenomena to the laws of the natural sciences, providing a cornerstone to the scientific status of linguistics. Once focused on the comparison of distinct historical stages (like Latin versus French or Old English versus Modern English), the field now incorporates much research on language change qua process, including work on changes now underway. Since all aspects of language change, historical linguistics is directly connected to all subfields.