The bugs living on your face could tell us where your ancestors came from

The Problem

  • Everyone has microscopic mites (in the same class, Arachnida, as SPIDERS, y’all) on their face and body.
  • I repeat, everyone has face spiders. THIS MEANS YOU. Well, technically they live all over your body in your hair follicles and sweat glands. And they’re not technically spiders- just spider cousins. Phew. I feel MUCH better now that that’s cleared up…nope.
Hi, I'm here to haunt your nightmares! Hugs?
Hi, I’m here to haunt your nightmares! Hugs?
Photo credit: California Academy of Sciences
  • Most mites are totally harmless, but they can cause skin conditions like Rosacea in some humans.
  • Mites have been hanging out on humans for a very long time and moving from place to place with them, so scientists wanted to learn more about mite evolution and how it’s related to human evolution.
  • Scientists have studied other species such as rodents, lice, bacteria and viruses to learn more about human evolution and where we came from, but not much is known about the genetics of mites or how they move from host (human) to host.

The Study

  • Researchers collected mites from 70 humans from across the globe.
  • They did this by scraping the curved end of a bobby pin across the forehead of each person or scraping their cheeks/smile lines/cheek folds with small metal spatulas.
  • They looked at the mitochondrial DNA of 241 different mites from the 70 people. Mitochondrial DNA is commonly used to trace ancestry since offspring only get it from their female parent.

The Results

  • The results of the DNA study suggest that mites have been around for a very long time (possibly before modern humans).
  • The mites were found on people from four very different ancestral lines (from Africa, Asia, Latin America and Europe).
  • The DNA from the mites in the four groups were very genetically different from one another.
  • This could mean that the four different ancestral lines of mites may have split from each other as long as 200,000 years ago (by travelling on humans).
See, spiders are kind of adorable, no? I'm sure mites would be too if we could see them...or maybe not.
See, spiders are kind of adorable, no? I’m sure mites would be too if we could see them doin’ their mite thing on us…or maybe not.
  • Scientists found that where people came from originally predicted what types of mites live on them.
  • For example, a person that was born in Asia but moved to the U.S. eight years ago still carried mites most often found on other Asians in the study.
  • They also found that mites didn’t migrate very much from person to person, so you’re much more likely to share mites of the same genetic line with your family or close friends than with people you aren’t related to (because the family that shares mites together, umm, has the same mites?).
  • They found several examples of African American participants whose ancestors have lived in the U.S. for many generations, but they carried mites only seen in other people from African, Asian, and Latin American ancestry even though they and their ancestors often came into contact with people from European descent. these African Americans have kept the same mite ancestral lines that came with their ancestors from Africa many generations ago.
  • People of European descent only had one type of mite on them. This suggests that some types of mites can only live on some types of skin (the other types of mites have died off over time).

The Takeaway

  • Mites were most likely living on humans when humans began to migrate across the globe.
  • Mite ancestry has split in a way that’s consistent with our theory of how human populations have split due to migration.
  • Mite ancestry supports the “Out of Africa” hypothesis* of human evolution and migration. WHAT??!! How cool are face spiders mites??!!
  • Because almost everyone has mites on them, scientists want to continue to study the genetics of mite ancestral lines to better understand how humans have evolved and moved to different places over time.
  • Your mites are a mighty line of mites that have passed down their DNA over thousands of years and survived the shenanigans of your ancestors just to be here with you today. Let’s show them a little love! I have no idea what that would look like, but maybe don’t scratch your face? Ugh.
  • The next time you feel lonely, just remember, you’re the most important person in the world to hundreds of thousands of mites. You’re welcome.

Question: To help scientists figure our where your ancestors came from, would you rather get your face scraped for mites or get blood drawn? Mites all the way for me!

I’m just going to leave this super magnified picture of mites burrowing into someone’s skin right here…
Photo Credit: Eye of Science/Science Source

*This is a widely accepted theory about the origins of humanity that states that every living human today is descended from a group that evolved in Africa and then spread out across the planet.

Itching for more info on mites? Read more here:
Global divergence of the human follicle mite Demodex folliculorum: Persistent associations between host ancestry and mite lineages, PNAS,

Author: Emily

I started Rise and Sci because I love science, I love teaching people new things and I want to help build a greater public understanding of all things science. My goal is to take hard to understand concepts and make them accessible to everyone- all in a fun an interesting format!

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