He might have shaved it once it got too bald-looking for his taste.
Beileve it or not, my hair has been slowly vanishing since 1999. At the time, I was only 27, and I was very upset, assuming it would be all gone by 40. Here I am near 50, and while I've lost a lot more since then, I still don't have a bald appearance. The fact that I'm tall is very helpful here, as people can't see my bald spot on top unless I'm sitting down.