On IRC, papermachine mentioned incredulity that horse collars took so long to be invented - a millennia or two to not choke your horses? I commented this had always struck me as pretty bizarre too, and I had long wondered whether there was some unmentioned factor at play (suggesting that either wooden plows didn't put enough weight to choke horses or that the choking only happened after horses were substantially enlarged after centuries of breeding).

He went looking on Wikipedia and indeed found subleties not usually mentioned:

While Lefebvre's experiments clearly demonstrated that the throat and girth design he used rode up on horses and cut off their air, images from ancient art and partial yokes found by archaeologists suggested that with proper placement and the addition of a stiff partial yoke, the breastcollar remained on the chest, and wind was not in fact cut off while pulling.[30][31] Further studies conducted in 1977 by Spruytte and Littauer, followed up by Georges Raepsaet, with more accurately reconstructed ancient designs suggested that horses with ancient harness designs could pull nearly as much as with the more modern horse collar.[32] The primary benefit to the use of the modern horse collar, it is argued, was that it allowed a lower point of attachment and in doing so the increased usability of horses for ploughing.[33]