Lice is life

This is the second in a series on the video What's The Problem With Nudity?
I remind the reader that I learned of this video after having first read and wrote about an article in the February 2010 issue of Scientific American (See my summary here). The calculations of time periods led to results in the video that differ somewhat from those in the Scientific American article, but they in the same ballpark.

The prevailing opinion among experts is that humans and chimpanzees descended from a common ancestor, and that the two species diverged about six million years ago. Because chimpanzees still have fur, the common ancestor of chimpanzees and humans must have had fur, too.

Which species of human was the first not to be covered in fur? Our own species has only been around for about a quarter of a million years. Were we the first humans to be naked? Or do we have to look further back?

Skin is not preserved in fossils, so evidence must be found somewhere else. Some decided to look for answers by examining lice. Human head lice were once all over our bodies. When our fur disappeared, the lice stayed in our heads, the only habitat left to them. DNA analyses show human lice and chimpanzee lice diverged at about the same time as humans and chimpanzees themselves.

But humans are rather unique in the animal world because they have three types of lice. In addition to head lice, we have pubic lice and body lice, that is to say, clothing lice.

The pubic or crab louse is different in size and shape from the head louse. It has adapted to holding on to larger hairs which are spaced farther apart. DNA tests show that its closest living relative is the gorilla louse. How did humans acquire the gorilla louse? At this time, there is no answer. We know, however, that lice are usually transmitted through physical contact.

In any case, the gorilla louse could not survive on humans before humans could offer a suitable habitat. This required that we first lose our fur and then develop pubic hair suitable to the gorilla louse. Of course, the gorilla louse passed on to humans has since evolved into what we now call the pubic louse.

According to DNA tests, the gorilla louse was passed on to humans some three million years ago. This was well before modern humans appeared about a quarter of a million years ago. In fact this indicates that complete nudity goes back to the time of Australopithecus. Since then, all descendants have had bare skin.

The body louse, which lives in clothing, is a direct descendant of the head louse. Like pubic lice, body lice could not adapt to this habitat until the habitat appeared. In other words, the body louse came to be when clothes were invented and used. The divergence occurred about 650,000 years ago. That’s when humans began to wear clothes regularly. So the ancestors of humans living today lived without clothes and without fur for nearly two million years.