Why Humans have Little Hair

I have an old diary that I wrote down lots of ideas in when I was a teenager.  Some of the ideas were stupid and obviously wrong.  Some of the ideas are stupid in that they are obviously right.  A few ideas I wrote down that I thought were obviously correct but I had never seen written anywhere.  Now with the invention of the Internet and web sites like Wikipedia it is easy to check whether some of these ideas are prevailing opinion or have even been thought of.

One brief note that I wrote was "humans evolved to have less hair after they invented clothes".  I have always thought this is fairly obvious but I have never seen any discussion of it, so I just did a search on the Internet.  There are many theories on why humans have little hair, but none of them mention the invention of clothes as having anything to do with it.  Here are three of the more plausible that I found.

One theory is that as humans became more sociable they lived in more close-knit groups and were far more susceptible to parasites.  Hair-loss was a way of dealing with the problem.  The problem with this theory is that there are many animals that live in close groups that have not lost their fur - for example chimpanzees preen each other  By the time humans were living this way they would have been intelligent enough to deal with parasites in some way.

Another theory is that at some stage humans became far more aquatic and lost their hair much like other animals have.  (Apparently pigs and elephants had aquatic ancestors which is the reason accepted for them being fairly hairless.)  Hair is not a good insulator in water.  I find it implausible and there is no archeological evidence for it whatsoever.

Perhaps the most plausible theory is that about 3 million years ago we lost our hair in the hot savannah of Africa (see http://www.scientificamerican.com/article.cfm?id=continuum-of-change).  The problem with this theory is that it is an advantage to have less hair in the heat of the day but also a disadvantage in the cool of the night.  Further, other animals in similar conditions have not lost their fur.  Also why when early humans moved into colder areas did they not grow the fur back again?

Clothes

It seems to me that the first humans who started hunting animals were intelligent enough to not only use the meat but also use the pelts of the animals they killed.  At first this might have just been for a bit of extra warmth at night (well before the use of fire).  Later they would have found ways to attach the furs to their torso, so it could be used during the day, but easily removed.  Being able to regulate body temperature by adding or removing clothing would have been a huge advantage over other animals.  To assist the use of clothes in regulating temperature, humans then evolved to have less hair and to use sweat to cool off when the clothing was removed.

When humans migrated into colder areas such as Europe their use of clothes was advanced enough that they did not need to grow their hair back.  With a large brain it is easier to obtain clothes than the extra food required for the skin to produce fur.   Also further from the equator there is a greater range of temperatures throughout the year.  Being able to regulate body temperature by adding and discarding clothes would still be a large advantage.

I am not sure why this is not commonly accepted or at least considered to be a plausible theory.  I am happy to hear any feedback on the subject.