Exploring Earwax, Genetics and Human Migration

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Have you ever pondered why earwax comes in different shades of colour and textures? Well, it turns out that your genes hold the answer! And the colour and texture of your earwax can tell a story of your ancestors’ migration journey.

Wet, yellowish-brown coloured earwax is commonly found in Caucasians and Africans. The other type is the dry, grey-white coloured earwax, which is more common among East Asians like Chinese, Korean, Japanese, and Native Americans.

Even more interesting is that this wet and dry earwax variation has been traced back to human migration patterns. This mutation may have begun when humans moved out of Africa and into Asia and Europe between 70,000 and 100,000 years ago.

However, it wasn’t until 2006 that researchers in Japan discovered the type of earwax people have is determined by a single mutation in the ABBCC11 gene.

This article will explore what earwax type can tell us about human migration and the ABBCC11 gene mutation that determines your earwax type.

But first, let’s take a brief look at the significance of the ABCC11 gene for human health more broadly to provide greater context and understanding of this fascinating topic.

ABCC11 Gene Discovery and Its Impact on Human Health

In 2001, researchers at the Tokyo Institute of Technology made a groundbreaking discovery: they found a new gene called ABCC11, also known as MRP8 (Multidrug Resistance-associated Protein 8). This exciting find opened up a new world of possibilities for understanding how our bodies work and how this gene impacts human health.

So, what exactly did these researchers do? They used advanced techniques to analyse DNA sequences and identify the ABCC11 gene. This was a challenging task, as the human genome comprises billions of DNA building blocks, and finding a specific gene is like searching for a needle in a haystack.

The discovery of the ABCC11 gene has significantly impacted genetics, as it has been linked to various aspects of human health.

The human ABCC11 gene plays a crucial role in our bodies by regulating various processes. This gene is like a tiny manager working behind the scenes to ensure everything runs smoothly. However, when alterations occur within this gene, it can have significant impacts on our health.

One of the roles of the ABCC11 gene is determining whether we have wet or dry earwax. While this might seem trivial, researchers have found associations between the ABCC11 gene and more profound health conditions, such as breast cancer, axillary osmidrosis (a disease causing excessive body odour), and drug resistance in cancer cells.

Studies have shown that certain variations in the ABCC11 gene can increase the risk of developing breast cancer. This discovery is significant because understanding the genetic factors in cancer development can help identify high-risk individuals and potentially lead to earlier detection and prevention measures.

In the case of axillary osmidrosis, the ABCC11 gene plays a role in producing apocrine sweat, which can contribute to body odour. By understanding this connection, researchers can potentially develop targeted treatments to alleviate the condition in affected individuals.

The ABCC11 gene’s involvement in drug resistance is particularly significant for cancer treatment. Some cancer cells can become resistant to chemotherapy drugs, making treatment less effective. Research has shown that specific changes in the ABCC11 gene can contribute to this resistance. Identifying patients with these gene alterations could allow doctors to personalise treatment plans, using alternative therapies or drug combinations to improve outcomes.

The discoveries related to the ABCC11 gene highlight the potential of personalised medicine, where treatments are tailored to an individual’s unique genetic makeup.

As we continue to learn more about the functions and implications of the ABCC11 gene, we can develop better strategies to prevent, diagnose, and treat various health conditions. In essence, this tiny gene may help unlock a new healthcare era that is more effective and personalised than ever.

What Do Earwax and Early Human Migration Patterns Have in Common?

Now you know there are two earwax types – wet and dry. East Asians usually have dry earwax, while other populations tend to have the wet type. Researchers discovered that a specific genetic variation in the ABCC11 gene determines which kind of earwax a person has. If someone has the AA genotype, they’ll have dry earwax, while GA and GG genotypes lead to wet earwax.

The Yoshiura et al. (2006) study provides data for the chart below, displaying the frequency of alleles A and G among different ethnic groups.

Graph of Allele Frequency in Ethnic Groups
Allele Frequency in Ethnic Groups

At a rudimentary level, the above chart displays ethnic groups with the driest earwax (Koreans) to the wettest earwax (African American) and everyone in between.

So, how did this wet vs. dry earwax gene mutation occur at a cellular level? It likely happened during meiosis (which is just a fancy way of saying cell division) and made its way into the human population through gamete-producing cells. And get this – it’s a recessive mutation, meaning you must have two copies of the A allele to express dry earwax.

Now, here’s where it gets interesting. Wet and dry earwax distribution tracks human migration patterns. If you’re of African or Caucasian descent, you’re more likely to have wet earwax. On the other hand, if you’re of East Asian descent, you’re more likely to have the dry variety. Pacific Islanders, South-East Asians, Native Americans, and Inuits have a more balanced mix of the two.

The chart below provides a more detailed view of the ABCC11 genotypes GG, GA, and AA and their frequency in different ethnic groups, as found in the Yoshiura et al. (2006) study.

ABCC11 Genotype Frequency in Ethnic Groups

But what about the Americas? Humans likely migrated to North America from Asia during a glacial period, but the frequency of the A allele in Native American populations is much lower than in Asia. It could be due to a founder event, where the A allele was at a lower frequency to begin with, or it could be because of a drop in population size following European settlement and interbreeding.

What does this have to do with tracing early human migration? The fact that the AA genotype is absent from African populations suggests that the mutation happened after humans started to spread out of Africa. It may have appeared in a “Mongoloid” founder population 40,000 years ago, which explains why the A allele is so common in East Asia.

We note that Mongoloid is now an obsolete term once used to categorise indigenous populations across extensive regions of Asia, the Americas, and certain areas in Europe and Oceania. This outdated classification originated from an invalidated theory of biological race. 

An elderly Asian gentleman appears to be having his ears cleaned.

In the above heartwarming photo by cheng feng on Unsplash, an elderly man sits patiently as another man attentively cleans his ears using simple tools and a head torch for precision. The scene shows ear cleaning as a more age-old tradition than we might expect.

As people migrated out of East Asia and interbred, the A allele made its way to other Asian countries, such as Japan. Where in 2009, Japanese researchers mapped the spread of the three genotypes.

The Japanese Earwax Gene Frequency Map: Tracing the Footsteps of Ancient Populations

In 2009, a nationwide collaborative study by the Super Science High School Consortium in Japan created a fascinating map showing the distribution of the earwax gene frequency across the country. This groundbreaking research offers unique insights into human migration patterns and holds promise for future medical research.

So, what exactly is earwax gene frequency? Simply put, it refers to how common a specific genetic variant is within a population. In this case, the researchers focused on the ABCC11 gene, which determines whether a person has dry or wet earwax.

By studying the distribution of this gene variant across Japan, they could better understand the migration and mixing of different populations or ethnicities throughout history.

The researchers hypothesised that the dry earwax type was brought to Japan by the Yayoi, who mixed with the Jomon population, which had predominantly wet earwax. They thought that the blending of these ancient groups had yet to finish, and the presence of the dry earwax gene would still be more common along the routes where the Yayoi people initially settled in Japan.

To test this hypothesis, the Super Science High School Consortium collected 1,963 fingernail samples from pupils and students in at least one high school or university in every prefecture across Japan. Their findings revealed distinct regional differences in the dry earwax gene variant frequency, supporting their hypothesis.

This earwax gene frequency study has significant implications for understanding population migration and the mixing of ancient Japanese populations. The results provide valuable insight into the region’s complex history of human migration, allowing scientists to trace the movement of people within Japan and potentially offering clues about ancient human migration patterns worldwide.

Beyond its historical significance, studying earwax gene frequency opens up new possibilities for medical research and genetics. For example, the ABCC11 gene has been linked to various health conditions, such as breast cancer risk and drug resistance in cancer cells. By having a comprehensive map of the gene frequency, researchers can target specific populations for further study and potentially develop more effective treatments based on genetic factors.

In conclusion, the 2009 Japanese map of earwax gene frequency is a prime example of how understanding our past can unlock essential information about our ancestry and human evolution. The potential future applications of this study in medical research and genetics are vast, demonstrating the interconnectedness of our world and the remarkable power of scientific inquiry. 

Why Did Wet and Dry Earwax Types Evolve?

Researchers believe that the ancestors of East Asians lived in a much colder environment than Africans. Those with a specific gene A allele might have had an advantage, like sweating less, to adapt to the cold climate.

To test this “cold adaptation hypothesis,” they looked at the connection between the frequency of this gene and how far away from the equator (absolute latitude) people lived in various populations.

They found that the frequency of this gene was indeed related to absolute latitude in Asian, Native American, and European populations. Interestingly, this wasn’t the case for other genes they tested as controls.

This means that the relationship between the ABCC11 gene and latitude is unique, supporting the idea that it could be linked to cold adaptation.

However, the researchers also point out that other factors related to latitude, like sunlight or the types of microbes around, could also play a role, and they can’t rule them out completely.

Let's Take a Moment to Appreciate Earwax

It’s fascinating to think that something as seemingly mundane as earwax could teach us so much about our ancestors’ movements. This shows how powerful genetics is when understanding our history.

By studying the distribution of this mutation and its prevalence in different populations, researchers can create a clearer picture of how our ancestors migrated and adapted to various environments.

Understanding molecular genetics and human evolution is crucial for the scientific community and the broader public. It allows us to appreciate the rich diversity of our species and the intricate interplay between genetics and environmental factors that have shaped human history.

So, next time your having your ears cleaned, take a moment to appreciate that earwax genetics and human migration are more closely linked than you might have thought. Who knows – you might even learn something about your ancestral origins!

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Bronwyn Lewis
Bronwyn Lewis
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5 months ago

Fascinating!

Lynne
Lynne
Guest
2 months ago

My doctor told me today that I’m in the 3% of Caucasians who have dry earwax. I googled out of curiosity and found your article. Who would have thought earwax could be so interesting?

Mark Behnke
Mark Behnke
Guest
2 months ago

Great details, thank you. As an American born of European ancestry, I discovered decades ago that my ear wax was dissimilar from most of my compatriots there. i.e., I have the dry type. I have occasionally wondered for this, and other reasons, about my genetic deep ancestry and just how a supposed European in North America ended up with the atypical ear wax type. I suppose living here in New Zealand now my ear wax makes me even less common except among the Asian population residing here.

Andrew
Andrew
Guest
2 months ago

Wow, so my dry ear wax type is associated with less BO? I guess that’s why I can get away with not showering for 3-4 days as long as I didn’t get sweaty. That could be a survival advantage – making it easier to attract a mate. 🙂

Angela
Angela
Guest
1 month ago

I have dry earwax & no body odor. My ancestors are Scottish (maternal) & Croation (paternal). Per my research, my maternal ancestors 4th ggparents were Cherokee from North Carolina. I have found no East Asian ancestors. No one else in my family have the traits. Since this is a recessive gene…..where did it come from & what are the odds?

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