Fossils, artifacts and human DNA sketch out the story of our evolution — but fail to capture everything. To fill in the gaps, some researchers are consulting our tiny hitchhikers: lice, mites and other parasites that latched onto our lineage long before Homo sapiens even evolved.
“If they’ve gone through the same history,” says University of Florida biologist David Reed, “[they] must have something to say about that history.” It turns out the parasites can reveal aspects of our past — including the invention of clothing, unknown migrations and close encounters with other species — overlooked by traditional lines of evidence.
Of Lice and Men
After studying lice on gophers as a graduate student, Reed turned his attention to hominins — species on the human branch of the primate family tree. In a field full of anthropologists, “I was the weird louse guy,” Reed says.
Lice have feasted on humans for ages. The insects have been recovered from mummies and other human remains up to 10,000 years old — but our shared evolutionary story goes much further back. Bloodsucking lice have essentially been stranded on the mammals they’ve infested for more than 70 million years. When host lineages underwent speciation, migration or extinction, so did the parasites, leading to today’s louse diversity: more than 500 species sucking on particular mammal types. The evolutionary trees of host and louse grew in tandem — most of the time.
