Comment by vanderZwan
4 hours ago
There's a hypothesis that sign language evolved before vocal languages, and that the latter "took over" as the default because it's energetically much more efficient. There's lots of circumstantial evidence but of course it's impossible to ever conclusively prove. This feels like another data point in favor of it.
As stated, this is too vague to be much of a hypothesis. Animals, including humans, communicate multimodally, so gesture and vocalisation are not mutually exclusive evolutionary stages. To claim that one evolved before the other, you'd need to define some relevant markers, such as grammar, cultural transmission or some anatomical adaptation.
Well I wasn't about to spend hours looking up sources and details specifying this hypothesis. All I remember now is that it's one that's taken seriously.