Sign languages are not new but just not as well documented and researched as spoken languages because pre film/video where was no easy way to record language us

Sign languages are not new but just not as well documented and researched as spoken languages because pre film/video where was no easy way to record language use. Most sign languages have no writing system. Additionally for the past 150 years the deaf community have been oppressed. Some researchers think some sign languages date back further than the first spoken languages.