The first humans were covered in fur. Once we created fire it was common to feel colder when away from the fire. This led to the creation of clothes. Once humans had created clothes to stay warm away from the fire they started shaving their bodies in order to display rock hard muscles to their mates in order to get laid. Over time only the strongest of hairs survived the constant shaving which is why we still have limited and varying degrees of body hair today. It used to be a very politically contentious subject on if it was moral to shave a baby or if you should wait until they were old enough to shave themselves. The down side to waiting for the pro shaving portion of the population was that the babies hair would thicken significantly as they aged if you waited. This would create a major disadvantage to them if they wanted to display as smooth chiseled tone as an adult. It is important to remember that back then adulthood was commonly accepted to start at the age of 12. The anti shaving populace quickly fell out of favor as a significant majority of humans would ultimately end up shaving regardless and it is undeniable that a major evolutionary advantage existed for those who were shaved as babies.