Many readers are echoing this expert:
As an evolutionary biologist, I just had to add my two cents to the baldness discussion. Not every trait needs to be adaptive. In fact, many traits are invisible to natural (or sexual) selection because they don't appear until AFTER individuals have reproduced. Take many late-onset diseases like cancer or Huntington's disease. By the time a person is afflicted by the disease they've often already had children and their genes have been passed on. Remember, it was only after the advent of modern sanitation that humans in large numbers began living past the age of 40 or 50. Baldness may be a consequence of hormonal changes in older individuals that cannot be shaped by natural selection because, for all intents and purposes, that person is already genetically "dead" (i.e. post-reproductive).
Another writes:
I can offer a personal anecdote regarding the advantages of baldness:
I am a 25-year-old management consultant. I spend most week days visiting clients across the US and Europe. I advise senior executives across a range of industries, on issues including where to invest and how to manage their businesses. Again, I am 25 years old. I also, fortuitously, have a receding hairline and a growing bald spot. My clients don't realize that I am 25. I suspect that most of them think that I am in my mid-30s. There are plenty of 25-year-old consultants, but few are able to go as deep with clients into as trusted a relationship. Pre-mature baldness allows me to fill the role a mature, time-wizened advisor.
The Dish 