The article mentions some possible advantages of speech over gestures: (1) Abstractness (which it debunks, I think successfully). (2) Better in the dark. (3)

The article mentions some possible advantages of speech over gestures: (1) Abstractness (which it debunks, I think successfully). (2) Better in the dark. (3) Frees the hands. (4) Energy usage. There are some others I can think of, too: (5) Not only does it free the hands of the speaker, it frees the eyes of the listener. I can only look in one direction at a time. If you're trying to communicate to me about a task I'm doing which involves looking at something, with gestures I need to shift my gaze to you and then back to what I'm doing. This makes real-time coordination of physical tasks difficult. (6) Distance. If two people are far apart (say, 100 meters), they can shout and be understood. With gestures, that could be possible but only if they involve large movements. Verbal communication can be scaled to large distances with a more straightforward modification. (7) Vision problems are more prevalent and strike at a younger age than hearing problems. What percentage of otherwise-healthy 35 year old people have myopia vs. have hearing loss?