Based on the review, his thesis seems fragile. Who says we don't "groom each other?" Maybe not in his circles. However, I will concede that our culture is irrationally touch phobic, probably due to religious taboos, not to natural tendencies. Indeed, I wonder just how much our humanness, or lack thereof, is informed by our taboos. And since other primates don't have glottises shaped the way ours are, they can't form words as we do. But that's a "chicken/egg" business.