We asked what common parasite anthropologists have used to determine a possible date of origin for the first human clothing. The parasite was used because clothing is far too perishable to appear in the fossil record.
Anthropologists have used body lice, specifically pediculus humanus humanus, as a chronological signpost to the origins of human clothing because, appropriately enough, human clothing is the body louse's natural habitat. Indeed, the body louse adapted specifically and exclusively to survive in worn human clothing, and anthropologist Mark Stoneking argues that the age of the body louse species is comparable to the first appearance of humans wearing clothes.
The logic behind the theory is straightforward enough, but actually determining the point in history that body lice first appeared requires the use of a controversial technique from genetic archaeology: the molecular clock. The molecular clock measures the age of one species by noting the number of differences between its mitochondrial DNA and the mitochondrial DNA of a second related species.
Since mitochondrial DNA isn't subject to genetic changes during reproduction, any changes are the result of mutation. By establishing a statistical rate at which mitochondrial mutations occur, scientists can use the number of differences between the two species to calculate how long ago they diverged.
According to Stoneking's molecular clock measurements, the human body louse broke away from its sister species, the head louse, 70,000 years ago. So, according to Stoneking's theory, humans have been wearing clothing for at least 70,000 years. And you thought your old clothes were out of date.