# Genetic and anthropometric studies on Japanese people

In population genetics, extensive research has been done on the genetic origins of modern Japanese people. Genetically, Japanese people mainly descended from the Yayoi people, the heterogeneous Jōmon population, and the recently proposed, but mildly debated Kofun period influx. Modern analysis categorize the Japanese into three separate but related groups: Ainu, Ryukyuan and Mainland (Yamato).
Anthropologically, Japanese people are closely related to clusters found in Northeastern Asia with the Ainu group being most similar to the Ryukyuan group, the Ryukyuan group being most similar to the Yamato group, and the Yamato group being most similar to Koreans among other East Asian people.

## Origins
### Dual ancestry theory

A common origin of Japanese has been proposed by a number of scholars since Arai Hakuseki first brought up the theory and Fujii Sadamoto, a pioneer of modern archaeology in Japan, also treated the issue in 1781. But after the end of World War II, Kotondo Hasebe and Hisashi Suzuki claimed that the origin of Japanese people was not the newcomers in the Yayoi period (300 BCE – 300 CE) but the people in the Jōmon period. However, Kazuro Hanihara announced a new racial admixture theory in 1984. Hanihara also announced the theory "dual structure model" in English in 1991. According to Hanihara, modern Japanese lineages began with Jōmon people, who moved into the Japanese archipelago during the Paleolithic. Hanihara believed that there was a second wave of immigrants, from Northeast Asia to Japan from the Yayoi period. Following a population expansion in Neolithic times, these newcomers then found their way to the Japanese archipelago sometime during the Yayoi period. As a result, miscegenation was common in the island regions of Kyūshū, Shikoku, and Honshū, but did not prevail in the outlying islands of Okinawa and Hokkaidō, and the Ryukyuan and Ainu people continued to dominate there. Mark J. Hudson claimed that the main ethnic image of Japanese people was biologically and linguistically formed from 400 BCE to 1,200 CE. Currently, the most well-regarded theory is that present-day Japanese are descendants of both the indigenous Jōmon people and the immigrant Yayoi people.
On the other hand, a study published in October 2009 by the National Museum of Nature and Science et al. concluded that the Minatogawa Man, who was found in Okinawa and was regarded as evidence that the Jōmon people were not a homogenous group and that these southern Jōmon came to Japan via a southern route and had a slender and more neo-Mongoloid face unlike the Northern Jōmon. Hiroto Takamiya of the Sapporo University suggested that the people of Kyushu immigrated to Okinawa between the 10th and 12th centuries CE. Regardless, both Northern and Southern Jōmon were craniofacially different from modern Mainland Japanese and had European-like features and a 'well-defined and less flat upper face' respectively. But they still had hair and teeth morphology that was characteristic of East Asian peoples, especially Northern Jōmon.
* A 2011 study by Sean Lee and Toshikazu Hasegawa reported that a common origin of Japonic languages had originated around 2,182 years before present.
* A 2015 study revealed that modern Japanese possess 2.2% West Eurasian ancestry, which likely originated from interactions with Silk Road traders around 1700 years ago.
The modern Japanese cluster is said to be the most similar with the Korean one; in a haplotype-based study, the Japanese cluster was found to share 87–94% of its genetic components with the Korean cluster, compared with a Han Chinese result of only 0–8%, a distinct contrast. Moreover, the genetic affinity to the Korean cluster was particularly strong among a cluster hailing from Shimane specifically and Honshu more broadly, but relatively less pronounced, albeit still overwhelming, in the Kyushu clusters. In any case, however, the study clarifies that "the estimate of ancestry profile cannot provide the definitive history of original migration, unless it will be further verified against historical evidence." Some studies suggest a genetic connection between Koreans and Southeast Asian populations. A 2017 study by Ulsan University analyzed a 7,700-year-old skull in Korea, finding evidence of genetic links to ancient populations, including those from Southeast Asia, such as Vietnamese people. This research highlights the complex migration patterns in East Asia’s prehistory. Similarly, Japanese research conducted in 1999 proposed that the Yayoi people, an ancient population contributing to modern Japanese ancestry, may have migrated from the Yangtze River basin in southern China. This was supported by DNA analyses showing similarities between Yayoi remains in southwestern Japan and early Han Dynasty remains from China’s Jiangsu Province. However, other studies suggest that modern Koreans share closer genetic ties with Central Asian and Northern East Asian populations. A mitochondrial DNA analysis revealed a genetic affinity between Koreans and Mongolians, indicating a shared Central Asian ancestry. Additionally, genetic research suggests that while Koreans share some common ancestry with other East Asian populations, their genetic ties with the Chinese are relatively more distant. Genome-wide studies further demonstrate that Koreans are genetically closest to Yamato Japanese and Manchu populations, reflecting shared ancestry and historical interactions, while genetic connections between Koreans and Southeast Asians are more limited.
* The origins of the Jōmon and Yayoi people have often been a subject of dispute, and a recent Japanese publisher has divided the potential routes of the people living on the Japanese archipelago as follows:
** Aboriginals that have been living in Japan for more than 10,000 years. (Without geographic distinction, which means, the group of people living in islands from Hokkaido to Okinawa may all be considered to be Aboriginals in this case.)
** Immigrants from the northern route (北方ルート in Japanese) including the people from the Korean peninsula, mainland China and Sakhalin Island.
** Immigrants from the southern route (南方ルート in Japanese) including the people from the Pacific Islands, Southeast Asia, and in some context, India. However, a clear consensus has not been reached.
* A study in 2017 estimates the Jōmon ancestry in people from Tokyo at approximately 12%.
* In 2018, an independent research conducted by director Kenichi Shinoda (篠田 謙一) and his team at National Museum of Nature and Science was broadcast on NHK Science ZERO and it was discovered that the modern day Japanese are genetically extremely close to the modern day Koreans. A genome study (Takahashi et al. 2019) shows that modern Japanese (Yamato) do not have much Jōmon ancestry at all. Nuclear genome analysis of Jōmon samples and modern Japanese samples show strong differences. Various studies estimate the proportion of Jōmon ancestry in Japanese people at around 9-13%, with the remainder derived from later migrations from Asia including the Yayoi people.
   Recent studies have revealed that Jomon people are considerably genetically different from any other population, including modern-day Japanese.
* Gyaneshwer Chaubey and George van Driem (2020) suggest that the Jōmon people were rather heterogeneous, and that there was also a pre-Yayoi migration during the Jōmon period, which may be linked to the arrival of the Japonic languages, meaning that Japonic is one of the Jōmon languages. This migration is suggested to have happened before 6000BC, thus before the actual Yayoi migration.
Some theories propose that the Yayoi people introduced wet rice cultivation to Japan from the Korean peninsula and Jiangnan near the Yangtze River Delta in ancient China. Additionally, some scholars suggest that the Yayoi and their ancestors, the Wajin, may have originated from areas like Yunnan province in southern China. Suwa Haruo argued that Wa-zoku (Wajin) might have been related to the Baiyue (百越).
* According to Alexander Vovin, the Yayoi were present on the central and southern parts of Korea before they were displaced and assimilated by arriving proto-Koreans. A similar view was raised by Whitman (2012), further noting that the Yayoi are not closely related to the proto-Koreanic speakers and that Koreanic arrived later from Manchuria to Korea at around 300 BC and coexisted with the Japonic speakers. Both had influence on each other and a later founder effect diminished the internal variety of both language families.
* Jared Diamond, the author of Guns, Germs, and Steel, suggested that the Yayoi period in Japan was initiated by immigrants from the Korean peninsula. Citing research findings, he stated that Yayoi Japan likely received millions of immigrants from Korea. These immigrants, during the Yayoi transition, are believed to have overwhelmed the genetic contribution of the Jōmon people, whose population was estimated to be around 75,000 at that time.
* Recent full genome analyses in 2020 by Boer et al. 2020 and Yang et al. 2020, reveals some further information regarding the origin of the Jōmon peoples. They were found to have largely formed from a Paleolithic Siberian population and an East Asian related population. Gakuhari et al. (2020) stated that the Jōmon had strong genetic affinities with Taiwanese aborigines.
* According to a March 2021 study on genetic distance measurements from a large scale genetic study titled 'Genomic insights into the formation of human populations in East Asia', the modern "Japanese populations can be modelled as deriving from Korean (91%) and Jōmon (9%)."

### Tripartite ancestry theory

A September 2021 study published in the journal Science Advances proposed that the people of Japan bore genetic signatures from three ancient populations rather than just two as previously thought.
* Proposed tripartite styled genomic transitions in parallel with cultural transitions in pre- and protohistoric Japan. (2021)The study states that in addition to the previously discovered Jōmon and Yayoi strands, a new strand was hypothesized to have been introduced, most likely from the southern Korean peninsula, during the Yayoi-Kofun transition period that had strong cultural and political affinity with Korea and China. According to the study, the genetic profile of the Japanese population was established in the Kofun period. Over 70% of their genetic makeup can be attributed to the Kofun component, with 15-20% being attributed to Yayoi and the rest to the Jōmon component.
* In the same year, The Nikkei published an article that showed the Kofun strand in modern-day Japanese was concentrated in specific regions such as Kinki, Hokuriku and Shikoku.
* Rui Wang (王瑞) and Chun-Chao Wang (汪群超) (2022) reiterated that Yayoi immigrants did not demographically replace the Jōmon. Instead, they co-existed and intermarried with indigenous Jōmon, which led the Yayoi to have 60% Jōmon ancestry. The rest was Northeast Asian. Jōmon admixture was decreased when ancestries related to the Northern Han Chinese were introduced in the Kofun period.
* Xiaoxi Liu (刘小晰) et. al (2024) stated that Jōmon admixture in contemporary Japanese people varies depending on region, with admixture being the highest in southern Japan, especially Okinawa (28.5%), followed by northeastern Japan (19%) and western Japan (12%). They also noted that the East Asian strand (labelled "Kofun") was dominant in western Japan while the Northeast Asian strand was dominant in northeastern Japan. However, Liu's research indicates a diminished number for the Kofun strand which was originally thought to have been over 70% in the previous papers, down to at most 35%. The rest consists of the aforementioned Jōmon strand and the northeastern strand labelled as "Three Kingdoms Korea" depending on the region.
However recently, the tripartite ancestry theory is being met with criticism since its introduction in 2021. In essence, Japanese researchers claim that a tripartite theory is redundant as the genetical difference between Yayoi and Kofun groups is not significant enough and that the temporal discrepancy of the periods is minuscule.
* According to Pere Gelabert in a 2022 paper, ancient Koreans of the Three Kingdoms period of Korea coded "Korea TK", bore close genetic similarity with Kofun period Japanese people. "The eight individuals from the Korean TK period are positioned within the diversity of East Asian individuals, particularly close to present-day Koreans and Japanese, ancient Kofun from Japan, and several Neolithic Koreans." He indicated that the Kofun strand was already present in the peninsula prior to it being introduced into the archipelago.
* A study published in April of 2024 by Hisashi Nakao (中尾 央), claims that the Kofun strand had much overlap with the previous Yayoi strand and that the two strands were genealogically closer than that of the Jōmon group. Nakao stated that "[the results] suggest that the Jōmon people were rather different from the Yayoi and Kofun people in the facial height and the anterior–posterior length [...] indicating that temporal differences are not significant among the Yayoi and Kofun periods. [...] the large overlap in morphological variation between the Yayoi and Kofun people could be an important step in further research." The research also boasts of using the largest Kofun samples to date.
* A recent study published by the University of Tokyo in October of 2024 also refuted the tripartite origin theory, claiming that the Kofun strand was not a single strand that was introduced separately into Japan, but a strand that was part of an already existing group within the Korean peninsula. According to the study, late-Yayoi period individuals carried both Yayoi and Kofun DNA, supporting Nakao's theory of lack of temporal differences between the two periods. The lead researcher and professor at the University of Tokyo's Department of Biological Sciences, Jun Ohashi (大橋 順) spoke with Science Daily, further explaining the new findings and criticizing the previous assumption. "Our results suggest that between the Yayoi and Kofun periods, the majority of immigrants to the Japanese archipelago originated primarily from the Korean peninsula," says Ohashi. "The results also mean the three-way admixture model, which posits that a Northeast Asian group migrated to the Japanese archipelago during the Yayoi period and an East Asian group during the Kofun period, is incorrect."
* A recent interview with the director of the National Museum of Nature and Science, Kenichi Shinoda (篠田 謙一) in December of 2024 summarized the current consensus in regards to the genomic makeup of the modern Japanese. Shinoda stated that over 90% of the modern Japanese DNA derives from an ancient strand that originated at an area near the Liao River around 50,000 years ago, where it was then introduced to the Korean peninsula (which in turn mixed with the Southern Jōmon-like inhabitants) and 10,000 years later was introduced into the Japanese archipelago. Shinoda also remarked that these migrations happened throughout the later Yayoi period and that the Japanese genes remained homogenous since then, stating that "the genetic makeup of the ancient Yayoi people and us (Yamato people) are almost identical". The director did not mention "Kofun", but insisted on calling the later settlers as "Toraijin (Immigrants)" or more specifically "later-Yayoi period settlers", despite taking part in previous studies surrounding the strand and mentioning it at the time of its proposal.

## Anthropometry

Stephen Pheasant who taught anatomy, biomechanics and ergonomics at the Royal Free Hospital and the University College, London, said that Far Eastern people have proportionately shorter lower limbs than European and black African people. Pheasant said that the proportionately short lower limbs of Far Eastern people is a difference that is most characterized in Japanese people, less characterized in Korean and Chinese people, and least characterized in Vietnamese and Thai people.
Rajvir Yadav et al. (2000) stated the sitting height to stature ratios of different populations: South Indian (0.4922), female Indian (0.4974), Eastern Indian (0.4991), Southeastern African (0.5096), Central Indian (0.5173), US (0.5202), Western Indian (0.5243), German (0.5266) and Japanese (0.5452).
Hirofumi Matsumura et al. (2001) and Hideo Matsumoto et al. (2009) said that the Japanese and Vietnamese people are regarded to be a mix of Northeast Asians and Southeast Asians. However, the amount of Northern genetics is higher in Japanese people compared to Vietnamese, who are closer to other Southeast Asians (Thai or Bamar people).
Neville Moray (2005) said that, for Korean and Japanese pilots, sitting height is more than 54% of their stature, with about 46% of their stature from leg length. Moray said that, for Americans and most Europeans, sitting height is about 52% of their stature, with about 48% of their stature from leg length. Moray indicated that modifications in basic cockpit geometry are required to accommodate Japanese and Vietnamese pilots. Moray said that the Japanese have longer torsos and a higher shoulder point than the Vietnamese, but the Japanese have about similar arm lengths to the Vietnamese, so the control stick would have to be moved 8 cm closer to the pilot for the Japanese and 7 cm closer to the pilot for the Vietnamese. Moray said that, due to having shorter legs than Americans, rudder pedals must be moved closer to the pilot by 10 cm for the Japanese and 12 cm for the Vietnamese.

### Craniometry

Ashley Montagu (1989) said that the "Mongoloid skull generally, whether Chinese or Japanese, has been rather more neotenized than the Caucasoid or European..."
Ann Kumar (1998) said that Michael Pietrusewsky (1992) said that, in a craniometric study, the cranial bones of Southeast Asians (Borneo, Vietnam, Sulu, Java, and Sulawesi etc.) are closer to Japanese, in that order, than Mongolian and Chinese populations are close to Japanese. In the craniometric study, Michael Pietrusewsky (1992) said that, even though Japanese people cluster with Mongolians, Chinese and Southeast Asians in a larger Asian cluster, the cranial bones of Japanese people are more closely aligned with several Mainland and Island Southeast Asian samples than with Mongolians and Chinese. However, Pietrusewsky (1992) also said, more research is needed on the similarity of the cranial bones between Japanese and Southeast Asians.
In a craniometric study, Pietrusewsky (1994) found that the Japanese series, which was a series that spanned from the Yayoi period to modern times, formed a single branch with Korea. Later, Pietrusewsky (1999) found, however, that Korean and Yayoi people were very highly separated in the East Asian cluster, indicating that the connection that Japanese have with Korea would not have derived from Yayoi people. However, in a follow-up study, Pietrusewsky (2010) corrected that East Asians and Southeast Asians were markedly separated from each other. He found that Koreans had the most similar cranial bones to ancient and modern Japanese including the Yayoi people and Jōmon people, followed by Taiwan and Hainan. He stated that a common origin of Northeast Asians could be traced and that they began entering the Japanese archipelago at the beginning of the Yayoi period.
Park Dae-kyoon et al. (2001) said that distance analysis based on thirty-nine non-metric cranial traits showed that Koreans are closer craniometrically to Kazakhs and Mongols than to the populations in China and Japan.
Torimitsu et. al (2024) states that there is quantifiable dimorphism in the cranium of Japanese people, similar to Thais, Indonesians, Filipinos and Malays. In addition, the nasal height and breadth of the Japanese were reported to be greater and smaller than Filipinos respectively, although Thais possessed greater nasal height and breadth than the Japanese. Japanese skulls also share some similarities with Hispanics, implied by the frequency of Hispanic skulls from southwestern United States being misclassified as Asian, particularly Japanese.