Well - I guess I misspoke by saying that Don's hair was definitely permed in the 70's. Of course, I don't know that for a fact. I didn't realize he had denied that he had ever had a perm.
However, if you look at pictures of Don from his very early childhood to current day, the only time in his entire life that his hair has been curly is during the 70's and I personally do not believe that is natural curl. It may not be a perm either, but I believe that his hair was styled somehow to get the curl. Maybe Don doesn't think it's very macho to divulge the methods used to obtain the curls.I have heard of people's hair getting curlier or loosing curl with age, but never heard of it going from completely straight to completely curly or vice versa. Anyway, from my own personal experience, I have naturally curly hair and the curl is very tight. I tried for years to get rid of the curl to no avail. I can style it to straighten it somewhat, but after a little while, the waves begin to reappear. I chemically straightened it once using a reverse perm. It was so straight, I couldn't do anything with it, but even that only lasted a few weeks before the curl started to return.
On a different note, I love the screenshots from that Houser video!