Hi, I’m Zukky.
I recently heard through social media that Mongolian spots are found in Finnish babies. Upon looking into it further, it seems this claim appeared in some older books.
As the name “Mongolian Spot” (Mongoloid Spot) suggests, it is a birthmark typically said to appear on babies of Mongoloid ancestry. Since Finns belong to the Caucasian group, where the spots are said to appear in less than 10% of infants, the finding of frequent occurrence in Finns would lend weight to the popular belief that Finns are of Asian descent.
This sounded fascinating, so I decided to investigate.
What Exactly Is a Mongolian Spot?
The Mongolian spot is a congenital birthmark that appears on the lower back or buttocks of infants. It was named by the German physician Erwin von Bälz (German: Mongolenfleck), who was hired by the Japanese government during the Meiji era.
The cause of the Mongolian spot is the melanin pigment. Although melanin is naturally dark (blackish-brown), when the pigment accumulates in the deep layers of the skin (dermis), light is scattered in the intervening layers (Tyndall effect), causing the spot to appear blue on the skin’s surface. However, the exact mechanism for why this accumulation happens in certain groups is not yet fully understood.
The first time I saw one, I was quite startled. I was changing a relative’s child’s diaper and saw a large birthmark there! I asked, “What happened to this mark!?” and then learned it was a Mongolian spot. So, I can only imagine the shock Erwin von Bälz must have felt when he first observed it.
When the spot was first named, it was thought to appear only in people of Mongoloid descent, including the Japanese. However, it is now known to appear in Negroid (Black) and Hispanic infants, and even rarely in Caucasians (White people).
So, at what rate do Mongolian spots actually appear in the Finnish population?
Prevalence of Mongolian Spots in Finns
The conclusion is that the rate of Mongolian spots in Finns is a mere 0.04% (2 out of 4,346 newborns) .
“Wait, isn’t that incredibly low!?” I was surprised myself when I looked it up.
In contrast, the prevalence rate for Caucasians in general is stated to be up to 10%.
From this data, we can conclude that Finns have a very low occurrence rate of Mongolian spots, even compared to the broader Caucasian population.
How Does This Compare to Other Ethnicities?
The Mongolian spot is not exclusive to Mongoloid populations.
| Ethnicity | Prevalence Rate of Mongolian Spots |
| Japanese | Almost 100% |
| Taiwanese | 61.6% – 90% |
| Chinese | 86.3% |
| Ainu | 46.3% |
| Turkish | 13.2% – 26% |
| Hispanic | 70% |
| Indian | 61.8% – 84.7% |
| Europeans | 1% – 10% |
| White Americans | 6.7% – 9.3% |
| White Australians | 13.3% |
| Finns | 0.04% |
I also tried to find similar data for the Sámi people, who are culturally related to Finns, but specific studies were not available.
Why Was the Myth of “Asian Finns” Formed?
The theory that Finns are of Asian descent gained popularity in Europe in the 19th century and was brought to Japan before World War II.
The basis for this was the now-discredited linguistic theory that Finnish and Japanese belonged to the same large linguistic group, the Ural-Altaic language family. Although this language theory has been refuted, the branched-off idea that “Finns are Asian” has persisted.
This narrative remains in older books, and the inclusion of the Mongolian spot likely stems from this trend. While it may be true that the spot was observed in Finns, the frequency was likely exaggerated in order to support the larger theory.
For a detailed explanation of whether Finns are truly of Asian descent, please see our separate article: “Are the Finns and Sámi People ‘Asian’? Unraveling the Complex Genetic Roots with Haplogroups“
Summary
Here is a summary of what we learned in this article:
- It is very rare for Mongolian spots to appear in Finns.
- From the perspective of Mongolian spot prevalence, Finns cannot be said to be genetically close to Asians.
Investigating a rumor heard on social media turned out to be quite educational! I look forward to sharing more things I discover that are not widely known.
引用文献
- Karvonen, S. L., Vaajalahti, P., Marenk, M., Janas, M., & Kuokkanen, K. (1992). Birthmarks in 4346 Finnish newborns. Acta dermato-venereologica, 72(1), 55-57.
- Kettner, M., Birngruber, C. G., Niess, C., Baz-Bartels, M., Bunzel, L., Verhoff, M. A., … & Ramsthaler, F. (2020). Mongolian spots as a finding in forensic examinations of possible child abuse–implications for case work. International journal of legal medicine, 134(3), 1141-1148.
- 菖蒲沢昇. (1959). 本邦人蒙古斑に就て. 日本医科大学雑誌, 26(7), 663-679.
- 日本形成外科学会『太田母斑・異所性蒙古斑（青あざ・真皮メラノーシス）』（https://jsprs.or.jp/general/disease/umaretsuki/hifu/otabohan.html）2025.12.8アクセス
- ex-Tokyo Medical University Genetics Study Group『About Mongolian Spots』Hironao NUMABE, M.D., Ph.D（https://cligen.org/english/mongolianspot.html）2025.12.8アクセス
- Science Direct “Mongolian Spot” （https://www.sciencedirect.com/topics/medicine-and-dentistry/mongolian-spot）2025.12.8アクセス
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