RICE AGRICULTURE IN THE YAYOI PERIOD

TECHNOLOGY IN THE YAYOI PERIOD

King of Na gold seal

Irrigation, agriculture (primarily rice farming), weaving and iron and bronze casting techniques were introduced to Japan from Korea and China between 300 and 100 B.C. Iron was used in weapons and farming tools. Bronze was made into swords, spears, “dotaku” (cylindrical bell-shaped objects) and mirrors used in religious rituals. The Yayoi people also used wooden ladles, hammers, ploughs and pestles. Yayoi pottery resembles pottery produced in Korea at the same time. The technique of weaving clothes arrived from China around 300 B.C. Early fabrics were made from hemp (for commoners) and silk (for nobility). Some were dyed red with an herb called madder.

“Although the pottery of the Yayoi was more technologically advanced--produced on a potter’s wheel--it was more simply decorated than Jomon ware. The Yayoi made bronze ceremonial nonfunctional bells, mirrors, and weapons and, by the first century A.D., iron agricultural tools and weapons. The Yayoi people lived in homes with proper entrances and windows, elevated floors supported by pillars, and roof ridges surmounted by ornamental wooden blocks. There were also high-floored warehouses and granaries. A 2000-year-old rice ball was discovered in the town of Rokuseimachi in Ishikawa Prefecture in December 1987.

It is believed that the ancient Japanese during this period traded with China and Korea. Archaeologists working on Ashibe, a small island 15 miles off Kyushu, have found coins and small mirrors from China and Korea and dugout canoes and port, but no evidence of large ocean-going ships.

In April 2009, a curator a museum in Shiga accidentally dropped and broke a 2,200-year-old Yayoi-period glass artifact that had been loaned to the museum by another museum in Saga.

Early Japanese History Websites: Aileen Kawagoe, Heritage of Japan website, heritageofjapan.wordpress.com; Essay on Early Japan aboutjapan.japansociety.org ; Japanese Archeology www.t-net.ne.jp/~keally/index.htm ; Ancient Japan Links on Archeolink archaeolink.com ;Essay on Rice and History aboutjapan.japansociety.org ; Metropolitan Museum of Art Department of Asian Art metmuseum.org; Wikipedia article on the Jomon Wikipedia ; Historical Parks Sannai Maruyama Jomon Site in Northern Honshu sannaimaruyama.pref.aomori.jp ; Yoshinogari Historical Park yoshinogari.jp/en ;Good Photos of Jomon, Yayoi and Kofun Sites at Japan-Photo Archive japan-photo.de ; Wikipedia article on the Ainu Wikipedia ; Good Japanese History Websites: ; Wikipedia article on History of Japan Wikipedia ; Samurai Archives samurai-archives.com ; National Museum of Japanese History rekihaku.ac.jp ; English Translations of Important Historical Documents hi.u-tokyo.ac.jp/iriki

Rice Agriculture in the Yayoi Period

null
replica of Yayoi storehouse Many archeologist looked upon the introduction of wet land rice farming techniques as the technological advancement that marked the beginning of the Yayoi period and the end of the Jomon period. In Kyushu people at red-kerneled rice.

Aileen Kawagoe wrote in Heritage of Japan: “The Yayoi farmers chose their rice field sites carefully. Initially, they preferred to choose not the swampy lowland locations that would be submerged by water most of the year, but high terraces or valleys backed by a hill or mountain were chosen. The Itatsuke site in Fukuoka was a settlement on a high terrace encircled by an oval moat. [Source: Aileen Kawagoe, Heritage of Japan website, heritageofjapan.wordpress.com ]

“However, as rice farming spread, and more and more land was cleared for farming, the Yayoi farmers needed more territory and moved into the alluvial plains. The mountains that surrounded the valleys and alluvial plains separated communities from each other, so that over the era various chiefdoms consolidated their control in marked territorities (such as Yamatai, Yamato, Kibi, Tsukushi, Izumo, etc.) in geographically distinct regions or areas.

“Immigrants must have arrived in northern Kyushu, in Japan from the Asian continent with their wet rice farming knowledge and advanced irrigation techniques at their beginning of the Yayoi period. This is clear because the technology did not show gradual innovations or advances but even the earliest Yayoi rice fields were already a complex system of canals, dams, paddy-field walls, and water intakes and outlets” to irrigate their fields. The immigrants had brought with them, new customs and traditions as well as their knowledge of how to make metal tools (iron and bronze). (While wet rice or paddy fields were cultivated and wet-rice agriculture flourished, dry-field agriculture was practiced as well elsewhere in Japan.)”

“Besides rice, 37 kinds of cultivated plants were known to have been grown, including foxtail millet, adzuki beans and barley. However, rice was the most important food, a fact shown by the high percentage that was recovered from excavations compared to other cereals.”

Rice Farming in Yayoi Japan

Kawagoe wrote: “Wooden stakes were used to outline or divide the rice fields which were enclosed by embankments walled with wooden planks. The Yayoi villagers dug ditches that sometimes doubled as defensive moats. Canals were built to ensure a constant and controllable water supply system for irrigating the rice paddy. At Itatsuke, the canals had a dam for collecting water with an outlet for letting water into the rice field. Also amazing were the drainage canals that had been constructed under the rice fields so that the water could be recycled and channeled back into the rice fields. [Source: Aileen Kawagoe, Heritage of Japan website, heritageofjapan.wordpress.com ]

“The Yayoi farmers had learnt by the 3rd century A.D., that they could improve their rice yield by transplanting rice seedlings from seedbed into paddy field in orderly and weedable rows. When the farmers created new rice fields or built their waterways and canals, they worked closely and cooperated with one another. They cultivated the fields with wooden rakes and hoes. The most common material used for making farming tools was hard oak wood. Stone hoes and reaping knives were used for harvesting rice. Some reaping knives were made of wood and shell but during the late Yayoi period, an iron edge was added to reaping knives made of wood. Reaping knives were often used together with the crescent-shaped sickles used for cutting at the base of the entire rice stalk.

“Few iron farming tools have been found, either because iron was still too scarce to be used for farming or because iron from the tools were constantly recycled and re-used. However, during the later part of the Yayoi period, iron tools began to replace stone ones. Iron provided sharper cutting edges so improving food production. The tools were durable and made tasks such as clearing of land for agriculture more efficient.

"Other wooden tools such as eburi or paddy field smoothers, ooashi or paddy field trampers, paddy field sandals and others were found at the Toro site in Shizuoka prefecture. Other objects also found at the Toro included ground stone arrowheads, ground stone axes, spades, fire-making mortars, weaving looms, and small boats for rice fields.

"They harvested the rice and stored the rice in storage jars in underground storage pits or in elevated storehouses (similar to those in southern China). At excavated sites like the Toro Ruins, a Yayoi farming settlement located in a coastal plain in Shizuoka prefecture, pottery recovered consisted of storage jars, cooking jars, pedestalled dishes and serving bowls.

"During the earliest Yayoi days, storage jars and a type of cooking pot that emerged in Kyushu and that had spread to southwestern Japan were clearly influenced by Korean mulmun plain pottery. But in other areas of Japan, Jomon styles of pottery modified or were incorporated into the Korean-influenced storage jars and cooking pots that were associated with agricultural uses."

Dating Rice Agriculture and Defining the Yayoi Period

carbonized rice grains from Nabatake site, 5th to 4th century BC

For a long time the earliest evidence of rice farming was dated to around 300 B.C. which worked nicely into models that it was introduced when the Koreans, forced to migrate by upheaval in China n the Warring States Period (403-221 B.C.), arrived around the same time. Later a number of Korean objects, dated between 800 and 600 B.C., were found. These discoveries upset the neatness of the model.

Then in the early 2000s, grains of wetland rice were found in pottery from northern Kyushu dated to 1000 B.C. This called into question the dating of the entire Yayoi period and caused some archeologist to speculate that maybe wet-land rice farming was introduced directly from China. This assertion is backed up somewhat by similarity in skeletal remains of 3000-year-old skeletons found in Quinghai province in China and Yayoi bodies unearthed in northern Kyushu and Yamaguchi prefecture.

Charles T. Keally wrote: “Exactly when, how and why rice farming first came to Japan is still one of the major controversies in Japanese archaeology. Rice has been found in sites dating about 1000 B.C., at the end of Late Jomon and the beginning of Latest Jomon. These sites, as far as I know, are all in Kyushu, except one, which is in Hachinohe on the Pacific coast of Aomori Prefecture, at the northern end of the central island of Honshu. Rice farming spread all over western Japan around 400-500 B.C. (uncalibrated radiocarbon age) and is also found in a number of sites in Aomori Prefecture, apparently spreading up the Sea of Japan coast along the Tsushima Current, together with the spread of one of the oldest recognized styles of Yayoi pottery, Ongagawa. Recent studies of plant opal (phytoliths) from Jomon sites claim possible evidence of domesticated rice in western Japan as early as 3000 B.C. or earlier, in Middle and possibly Early Jomon. [Source: Charles T. Keally, Professor of Archaeology and Anthropology (retired), Sophia University, Tokyo, net.ne.jp/~keally/yayoi ++]

“There is general agreement that the ultimate origin of rice is the east-central lowlands of China. A southern route via the Ryukyu islands into southern Kyushu seems generally out of favor. I think both the Chinese archaeological and environmental evidence argue strongly against a northern route via northeastern China and northern Korea, although some archaeologists do favor that hypothesis. The present evidence neither confirms nor denies either a direct route to Kyushu from China or a route via southern Korea.

Japan Rice Dated to 1000 B.C.

Yayoi-era foods

In May 2003, Japanese scientists at the National Museum of Japanese History (NMJH) in Chiba, outside Tokyo, announced that had dated rice samples from Yayoi pottery to 780 to 830 B.C. and said the results implied that rice agriculture in Japan dated back to 1,000 B.C.. Mineo Imamura, the chemist heading a project at the museum to scientifically date archaeological materials, sent food residue samples from 11 early Yayoi pottery pieces to an accelerator mass spectrometry lab in the United States. Dennis Normile wrote in Science magazine, “Results from 10 of the 11 pots put their ages at 780 to 830 B.C. Because there are more primitive Yayoi pottery samples, they speculate the actual start of the Yayoi period should be about 1000 B.C. Harunari says this indicates that the use of rice paddies spread eastward half a millennia before the Warring States period. The group presented their findings during the spring meeting of the Japanese Archaeological Association” on May 25, 2003. [Source: “Earlier Start for Japanese Rice Cultivation” by Dennis Normile, Science magazine, May 30, 2003]

The National Museum of Japanese History reported: NMJH has been conducting studies on the application of high-precision C14 dating techniques with the use of Accelerator Mass Spectrometry (AMS). This research was approved in order to confirm preliminary results that the Yayoi period had started in the 10th century BCE, or 500 years earlier than previous archaeological theories have proposed. At the end of 2003, NMJH established a research facility to create a framework for C14 dating experiments. With the award of the grant, the group decided to conduct nation-wide research on age determination, primarily of Yayoi period remains. [Source: “The Origin of the Farming in the Yayoi Period and East Asia: Establishment of High-Precision Chronology by Carbon 14 Age Analysis”, National Museum of Japanese History (NMJH), 2004 +++]

Another Yayoi food

“In the 2004 fiscal year, more than 2,000 samples of wood, seeds, and carbide residue on earthen vessels were extracted from 190 sites; among them, measurements were conducted on 500 samples. As a result, we speculate that irrigated rice cultivation of the Yayoi cultures first appeared in northern Kyushu approximately 930 BCE and that the “early Yayoi” period began around 800 BCE. We also tentatively concluded that “early Yayoi” culture appeared in the Chugoku and Kinai areas between 700 and 600 BCE, 100 to 200 years later than northern Kyushu. We are also beginning to get a clear picture of ocean reservoir effects and millet. +++

“The earliest archaeological sites are Itazuke site or Nabata site in the northern part of Kyushu. The origin of Yayoi culture has long been debated. Chinese influence was obvious in the bronze and copper weapons, dokyo, dotaku, as well as irrigated paddy rice cultivation. Three major symbols of the Yayoi Culture are the bronze mirror, the bronze sword, and the royal seal stone. +++

“In recent years, more archaeological and genetic evidence has been found in both eastern China and western Japan to lend credibility to this argument. Between 1996 and 1999, a team led by Satoshi Yamaguchi, a researcher at Japan’s National Science Museum, compared Yayoi remains found in Japan’s Yamaguchi and Fukuoka prefectures with those from early Han Dynasty (202 BC-8) in China’s coastal Jiangsu province, and found many similarities between the skulls and limbs of Yayoi people and the Jiangsu remains. Two Jiangsu skulls showed spots where the front teeth had been pulled, a practice common in Japan in the Yayoi and preceding Jomon period. The genetic samples from three of the 36 Jiangsu skeletons also matched part of the DNA base arrangements of samples from the Yayoi remains.” +++

Implications of the 9th Century B.C. Dating of Japanese Rice

Dennis Normile wrote in Science magazine, The “new dates for food residue scraped from ancient Japanese pottery have touched off a storm of controversy in Japan’s archaeological community. The findings play into the debate over how and when rice paddy agriculture spread from central China. “This could change our understanding of Asian antiquity,” says Hideji Harunari, an archaeologist at the National Museum of Japanese History in Chiba. [Source: “Earlier Start for Japanese Rice Cultivation” by Dennis Normile, Science magazine, May 30, 2003 +/]

“Rice cultivation in paddies is widely believed to have emerged along the Yangtze River in central China about 8000 B.C. How and when it spread eastward is less clear. One theory holds that immigrants fleeing the turmoil of China’s Warring States period, beginning about 450 B.C., took the technology overland to present-day Korea, then across the relatively narrow Korea Strait to Japan’s Kyushu Island. An alternative theory is that seafaring traders carried the technique to lands bordering the Yellow and East China seas around 1000 B.C. or earlier.

“In Japan, the spread of rice cultivation is one of the marks of the beginning of the Yayoi Period, which has been pegged to 500 to 400 B.C., mostly by speculative analysis of evolving pottery techniques. “There have really been very few actual measurements [of artifacts],” says Imamura. +/

“An earlier start for the Yayoi Period would also mean refiguring an important era in Japanese history. The spread of rice paddy agriculture led to population growth, increasingly large and sophisticated settlements, and chiefdoms. The consolidation of several chiefdoms led to the emergence of a prototypical Japanese nation mentioned in Chinese records of about A.D. 300. Harunari says if their new date for the start of the Yayoi Period is correct, this cultural process took 1200 years instead of the currently accepted 700 to 800 years. But Fujio Oda, an archaeologist at Fukuoka University, and others want more evidence before Japan’s history books are rewritten. “We really need a lot more data and not just results from one particular age,” Oda says. +/

Route of Rice Agriculture From China to Korea to Japan

Very old rice from the Hemudi site in eastern China

Kawagoe wrote: “Rice is thought to have originated from Hemudu and Pengtoushan area of China between 7,000 to 8,000 years ago. So why did it take around 5,000 years for rice agriculture to diffuse or spread to Japan? Archaeologists and historians believe that the time-lag in taking up rice farming for Japan was due to the roundabout route that rice took to arrive along with migrants into Japan. Rice was thought to have originated from Changjiang and brought to the Korean peninsula, then via the Korea-Tsushima strait into Northern Kyushu. There are two other possible routes over which migrants may have taken the rice to Japan (from southern China through the Ryukyu islands too southern Kyushu; or directly from Chanjiang to northern Kyushu) but most experts are currently agreed that archaeological evidence supports only the Korean route.” [Source: Aileen Kawagoe, Heritage of Japan website, heritageofjapan.wordpress.com]

Dr. Wilhelm Solheim’s hypothesized that boat-people plying their trades along the Chinese coast, seeking wider markets eventually arrived on the coasts of Korea and Japan, bring their rice culture with them. Keally wrote: “There they set up seasonal settlements. These settlements later became permanent, and the settlers farmed rice for their own use. This practice soon spread to the native peoples -- the Jomon people in Japan -- who added rice farming to their subsistence base while teaching the colonists aspects of their native way of life. As the colonists became well adapted to the new lands, their populations exploded, supplemented by immigrants from the Korean peninsula, perhaps trying to escape the turmoil caused by the collapse of the Chinese Chou Dynasty and the establishment and expansion of the Han Dynasty. There are many other hypotheses.” [Source: Charles T. Keally, Professor of Archaeology and Anthropology (retired), Sophia University, Tokyo, net.ne.jp/~keally/yayoi ++]

Kawagoe wrote: “Along with rice grains, Korean-style pottery, pit-dwellings, storage pits and stone tools similar to those found in Korea and shell harvesters, also appeared in Japan around the 400-500 B.C. date. Rice found in southern China (the original source) was of two kinds: long and slender grained, as well as short and fat grained. In Yayoi Japan however, only the short grained type of rice is found. Because rice is a subtropical plant used to being grown in warmer climates, it took time for rice to be adapted to the cooler climates of northern China, Korean peninsula and to Kyushu which was wet and cool during Yayoi times. As rice traveled with migrating tribes, the long and thin grained variety was discarded along the way, because short grained rice proved to be better suited to growing conditions in Korea and Japan.

“The earliest rice fields of Yayoi Japan ever discovered were in northern Kyushu at the Nabutake site in Saga prefecture, and in Fukuoka prefecture, at the Itatsuke and Notame sites. But the one excavated site that captivated everyone’s interest was at Toro in Shizuoka prefecture. Buried by a flood, the Toro rice farming village was preserved in particularly excellent condition. Although it had taken rice agriculture 5,000 years to take hold in Japan, once it did, rice farming as a way of life took less than 300 years to spread northwards and eastwards right across Honshu island all the way to the northern tip. Rice was cultivated in northern Tohoku before the Yayoi period came to an end.

“Rice farming spread from Kyushu eastwards and northwards to Shimane’s coastal plains and mountain valleys through two major routes: the “Sea of Japan” road along the Japan Sea coast and the “Mountain Road” over the Central Japan mountain ranges and the Yayoi village began to emerge in various regions.

Linguistic Evidence for the Spread of Rice Agriculture from East China to Korea and Japan

In 2012, John Whitman of the National Institute of Japanese Language and Linguistics at Cornell University wrote: “The languages of Northeast Asia show evidence of dispersal from south to north, consistent with the hypothesis that agriculture spread north and east from the vicinity of Liaoning, beginning with the millets approximately 5500 BP. Wet rice agriculture in Korea and Japan results from a later spread, also beginning in Shandong, crossing via the Liaodong peninsula and reaching the Korean peninsula around 1500 BCE. This dispersal is associated with the Mumun archaeological culture after 1500 BCE in the Korean peninsula and the Yayoi culture after 950 BCE in the Japanese archipelago. [Source: “Northeast Asian Linguistic Ecology and the Advent of Rice Agriculture in Korea and Japan” by John Whitman, Rice, December 2011, Volume 4, Issue 3-4, pp 149-158 January 14, 2012 ~]

“From a linguistic standpoint, it is associated with the entry of the Japonic language family, first into the Korean peninsula, subsequently into the Japanese archipelago. The arrival of Koreanic is associated with the advent of the Korean-style bronze dagger culture and a temporary hiatus in wet rice agriculture sites around 300 BCE. Both Koreanic and Japonic are relatively shallow language families, with Koreanic the shallower of the two, consistent with the chronology above. The gap between the earliest linguistically motivated dates for these language families and the archaeological events is the result of a linguistic founders effect, providing further evidence for demic diffusion as a source for their distribution. ~

“I have sketched a specific historical scenario that attempts to explain the linguistic ecology of the non-Sinitic language families in Northeast Asia associated with wet rice agriculture, Japonic and Koreanic. This scenario is couched within the general hypothesis of a diffusion of agriculture from the area around the Shandong peninsula to the north and east. According to the scenario, Japonic arrives in the Korean peninsula around 1500 BCE and is brought to the Japanese archipelago by the Yayoi expansion around 950 BCE. On this view, the language family associated with both Mumun and Yayoi culture is Japonic, although the association of a culture in the archaeological sense with a single language family is almost certainly an oversimplification. ~

“Koreanic arrives in the south-central part of the Korean peninsula around 300 BCE with the advent of the Korean-style bronze dagger culture. Its speakers coexist with the descendants of Mumun cultivators, and thus with Japonic, well into the common era. Each of these demic diffusions, as well as the later dispersions of Koreanic and Japonic, result in founder effects which diminish the internal variety of the language family. Japonic and Koreanic, as well as possibly other Northeast Asian languages, share some agricultural vocabulary, but this shared vocabulary precedes rice farming.” ~

Impact of Rice Agriculture on Yayoi Japan

Kawagoe wrote: Rice is a highly nutritious food and can be grown to feed and sustain a large population. It allowed for a stable settled lifestyle instead of a nomadic hunter-gatherer one. Archaeologists have noted that following the introduction of rice farming, the population in Yayoi Japan saw an astonishing increase in the number and size of its village settlements. Experts have estimated that the Yayoi population increased by between 25 times to 70 times over a thousand years beginning with the Yayoi era. Some of that increase was due to migrants from the Asian continent, but much of the population increase was also naturally due to the more stable source and quality of nutrition for the Yayoi people. [Source: Aileen Kawagoe, Heritage of Japan website, heritageofjapan.wordpress.com ]

“Rice farming technology also changed the way people did things, the way they lived and even changed social relationships for the people living in the Yayoi society. Rice grains and dry swidden rice field sites have been excavated in Kyushu dating to an earlier time around 1,000 B.C. But it is thought that at the time rice farming made no impact on Jomon culture nor did it affect the economic foundation of society. It wasn’t until half a century later when wet-rice farming techniques and agricultural tools appeared on the scene, that rice farming is considered to have been introduced on a full scale in Yayoi Japan. Around that time, migrants entered Japan in large numbers and brought with them crops and farming technology along with bronze and iron tools and objects.”

Did intensive agriculture bring more violence? Of the 5,000 skeletons excavated before the arrival of agriculture only 10 showed signs of violent death. Of the 1,000 dated after the arrival of agriculture more than 100 show such signs.

Fish Farming in the Yayoi Period

Fish farming in the form carp farming is believed to have originated in Japan in the Yayoi period. The conclusion is based on the discovery of fossils of young carp teeth at an archeological site near Nagoya in what appears to have been a moat. Kyodo reported: “People in the Yayoi Period might have engaged in carp farming to provide sustenance during the winter, a group of researchers said. According to the group, the find at the Asahi site in Aichi Prefecture, a huge moated settlement that existed from the fourth century B.C. to the fourth century A.D., suggests it engaged in what would be the earliest known form of carp farming in Japan. [Source: Kyodo, Japan Times, September 19, 2008]

Tsuneo Nakajima, the curator of the Lake Biwa Museum, which contains the fossils, told Kyodo, “I suppose Yayoi people released carp in the spawning season into rice fields, moats or ponds, and that the fish produced eggs — primitive farming probably started in such a way. In addition to adult fish caught in rivers, Yayoi people must have dried young fish they had bred to preserve for winter sustenance.”

The young carp teeth were found in a different place than adult teeth. It is unlikely the two groups occurred in separation like this naturally and thus suggests fish farming. The technology for fish farming is believed to have been introduced from China along with rice farming, Carp teeth were found in remains from the earlier Jomon Period but did not include those of young carp, which indicates Jomon people were unlikely to have engaged in fish farming.

Meat and Animals in the Yayoi Period

Deer was another important source of food. In some places they achieved divine status. They are often depicted on “haniwa”, ceramic figures placed around grave mounds, dating from A.D. 3rd to 6th centuries. Artifacts found at Yayoi sites have included stone sinkers for fishing nets and fish-hooks made of antler. Deer scapulae used for divination, indicated that the shaman religion played an important role in the society.

Kawagoe wrote: Wild boars were kept in the Yayoi village as during Jomon times. Archaeologists have also identified some excavated bones to be those of the domesticated pig, most certainly introduced from the mainland. The Yayoi people also continued to hunt animals and to fish, and gather wild roots, vegetables and fruit to supplement their rice-based diet. [Source: Aileen Kawagoe, Heritage of Japan website, heritageofjapan.wordpress.com ]

Image Sources: Wikimedia Commons; National Museum of Science, Tokyo kahaku.go.jp; Yoshinogari Historical Park yoshinogari.jp. Yayoi houses, Ray Kinnane

Text Sources: Aileen Kawagoe, Heritage of Japan website, heritageofjapan.wordpress.com ; Charles T. Keally, Professor of Archaeology and Anthropology (retired), Sophia University, Tokyo, ++; Topics in Japanese Cultural History” by Gregory Smits, Penn State University figal-sensei.org ~; Asia for Educators Columbia University, Primary Sources with DBQs, afe.easia.columbia.edu ; Ministry of Foreign Affairs, Japan; Library of Congress; Japan National Tourist Organization (JNTO); New York Times; Washington Post; Los Angeles Times; Daily Yomiuri; Japan News; Times of London; National Geographic; The New Yorker; Reuters; Associated Press; Lonely Planet Guides; Compton’s Encyclopedia and various books and other publications. Many sources are cited at the end of the facts for which they are used.

Last updated September 2016