Hadn't seen this old thread before. I worked in a shoe store for some years. As noted back in the thread, the theory was that man evolved walking on soft sand, where the heel sunk in further, so the negative heel is more natural. About 1980, the original manufacturer was looking for a buyer; they stated in a shoe industry publication that they wanted to sell to someone with the correct astrological credentals. So much for their "scientific" credibility...