What is remarkable are some of the theories of how the humans survived this period. One very famous theory is that humans moved to the litoral zones (e.g. - the seashore) and became semi-aquatic fish catchers for thousands of years, and in the process started to lose much of their body hair and become more 'streamlined' heading in the same evolutionary direction as the dolphins.
Hmmm. I suspect those with was less hair = less bugs = less disease. They survived to reproduce.