Parasitic Lice Help to Fill in the Gaps of Early Hominid History

Humans have been coevolving with three types of ectoparasitic sucking lice for millions of years. Head lice live primarily on the head and often cause undue anxiety and stress to parents of infected children. Body or clothing lice, as the name implies, live primarily in the clothing. They are generally bigger than head lice and can transmit deadly diseases. Pubic lice are sexually transmitted and are primarily found in the pubic region. An upside to the close association humans have with these parasites is that we are able to use the lice to learn about human evolutionary history. For example, understanding the biology of early humans has been historically challenging. Although fossils have provided evidence of the morphological changes that have occurred since the split between humans and chimpanzees, it has been much more difficult to study other attributes of early humans such as behavior or habitat use. Parasitic lice have provided some of this missing information. Herein we review what has been learned about human and primate evolution and behavior through studies of lice. We examine in detail the biology of the human pubic louse, which was transferred from a gorilla ancestor to a human ancestor about 3–4 million years ago. This particular host switch provides evidence of when humans lost their body hair and what habitats these early humans were using.