It's a little gross to consider, but every one of us has mites that live in our hair follicles. Most of the mites are found near our cheeks, nose, forehead, eyebrows, and eyelashes. These mites—which have elongated bodies and are semi-transparent when viewed under a microscope—are commonly called face mites. (The scientific moniker for face mites is Demodex folliculorum). These creatures are tiny arachnids (related to spiders) that consume dead skin cells and oil associated with hair follicles and sebaceous glands. D. folliculorum is usually harmless to humans, but in some instances can cause skin and eye problems.
Remarkably, scientists know very little about face mites despite their close relationship with humans. Scientists don't have a full understanding of the role mites play in human health nor do they know how these creatures are transmitted from human to human. To address this lack of understanding, an international team of scientists, headed up by an investigator from the California Academy of Sciences, recently characterized the genetic variability of D. folliculorum.1
Not only did their work turn out to be a landmark study—it also carries implications for human origins models.
Studying Mite Genetic Variability
These researchers analyzed D. folliculorum mitochondrial DNA (mtDNA) sequences isolated from 70 people who had ancestries from different parts of the world (Africa, Europe, Asia, and Latin America). They discovered different versions (called haplotypes) of face mite mtDNA that corresponded to the geographic ancestry of the human test subjects. In other words, people with a family history from Africa, Europe, Asia, and Latin America harbored face mites with characteristically distinct mtDNA, respectively.
The research team also discovered that the human hosts retained the same face mites after moving to new geographical locations. For example, they discovered that people who were born in Asia but later relocated to the United States had face mites characteristic of people from Asia, even after living in the United States for many years. The investigators also uncovered several instances in which people with African ancestry had D. folliculorum strains similar to African people groups, even though their ancestors came to the United States several generations ago.
The investigators learned that parents and children had the same face mites; but seldom did they observe the same types of face mites for people from different family units.
From these observations, the scientists concluded that face mite infection requires close and sustained physical contact and, therefore, occurs most frequently from parent to child. This pattern of transference closely mirrors the transmission of genetic material (which, of course, is from parent to child). Consequently, the genetic variability of face mites can serve as a proxy for the genetic variability of their human hosts.
In fact, the researchers point out that the pattern for the global genetic variability of face mite mtDNA is exactly what would be expected if the out-of-Africa model for humanity's origin is valid.
Accordingly, face mites infected human hosts shortly after humanity originated and then were carried with humans as they migrated around the world. Over time, distinct genetic variants of face mites emerged in geographically distinct regions of the world. Molecular clock analysis of the face mite genetic variability places their origin between 2 to 3 million years ago, well before modern humans appeared on the scene. However, the researchers from the California Academy of Sciences note that the mutation rates of mtDNA for parasitic arthropods is known to be 100-times faster than in nonparasitic arthropods.2 Considering this correction to the mutation rate of face mite mtDNA, the origin of human face mites aligns with the origin of modern humans, particularly the out-of-Africa model.
Face Mites and the Out-of-Africa Model
The out-of-Africa model proposes a scenario for human origins that closely aligns with the biblical description.
- Humans originated recently—around 100,000 years ago, plus or minus 20,000 years or so.
- Humans originated at a single location, namely East Africa—close to where some Bible scholars think the Garden of Eden was located.
- Humans originated from a small population of individuals.
Moreover, analysis of the genetic variability of human mtDNA (which provides insight into the origin of the maternal lineage) indicates that humanity traces back to a single ancestral sequence that could be interpreted as a single woman. Likewise, characterization of human Y-chromosomal DNA (which provides insight into the origin of the paternal lineage) indicates that all men trace their origin back to a single ancestral sequence that could be interpreted as a single man.
Though often presented and discussed within the context of the evolutionary paradigm, this model has profound biblical implications. If humanity's genesis happened in the way Scripture describes, then genetic diversity patterns observed among people groups around the world would be very similar to those discovered by anthropologists.
The agreement between the genetic variability pattern of face mites and that of humans provides independent support for the out-of-Africa model and, consequently, for the biblical account of humanity's beginnings.
Face mites are not the only "bugs" to impact the human origins debate. Researchers have also been able to trace the origin and migration patterns of humanity using several other types of pathogens and parasites. For relevant discoveries, check out the following articles: