The Mystery of the Domestication of Helianthus annuus L.: Is the Sunflower still North America’s only Domesticate?
Writer’s Comment: At the beginning of the PLB143 course, Professor Paul Gepts assigned a term paper on the crop of our choice. Though I am not a Plant Biology major, I enjoyed the class as well as the term paper’s research and writing process. Professor Gepts’ course taught me where the food I consume on a daily basis comes from, explained why some watermelons are striped and why bananas are sterile, and emphasized the importance of the domestication triangle. Eventually, I chose to research the origin of domestication of the sunflower because it was the crop I was most familiar with and most curious to learn about. I was fortunate enough to have access to valuable resources, such as the electronic databases from the campus’s library and conversations with professors who have published numerous articles in scientific journals. Now whenever I spot a certain flower with a brown center and golden yellow rays, I immediately think Helianthus annuus.
Instructor’s Comment: The transition from hunting-gathering to agriculture some 10,000 years ago was one of the most momentous processes in human evolution. As a consequence of this switch, people became sedentary, living in villages and cities. They invented and adopted new technologies such as ceramics, metallurgy, and alphabets. The division of labor afforded by agriculture led eventually to the development of ancient civilizations. Where, when, and how this transition happened can be inferred from studies on the origin and evolution of crop plants. Plant Biology 143 discusses how scientists actually determine the origin of domestication of crops through a combination of biological, archaeological, historical, and linguistic data. In her scientific review paper, Kristine Lalic provides an excellent in-depth discussion of the evidence for the origin of the sunflower in North America. Whether the sunflower was domesticated in what is now the eastern U.S.A. or in Mexico has recently become controversial because of contradictory genetic and archaeological data. The last word on this debate has not been uttered!
—Paul Gepts, Department of Plant Sciences
In this paper, I review linguistic, archaeological, and historical evidence for the original domestication of the sunflower Helianthus annuus L. This crop is the second most valuable oilseed crop produced today. It is found all over the world because of its ability to grow and adapt in the most disturbed environments. The sunflower’s center of origin and domestication was originally thought to be somewhere in central or eastern North America, but when researchers found older domesticated plant remains from archaeological sites in Mexico, the debate on the center of domestication was revived. Re-examination of the expansive library of data on the sunflower will help settle the debate about its center of origin and domestication.
In this review, I will first give an overview of general information about the sunflower crop, including botanical, nutritional, utilization, and production data. I will then review and discuss the information about the origin of domestication of this crop before ending with suggested lines of future research.
Helianthus annuus L. (H. annuus), or the domesticated sunflower, is a member of the Asteraceae or Compositae family, which is made up largely of flowering plants. It is a coarse annual plant that can grow from 7 to 9 feet tall (http://montana.plant-life.org, www.plants.usda.gov). It grows erect, is unbranched, and has fibrous roots (Weiss, 1983). The domesticated sunflower has a shallow but substantial root system. Its stem is green, rough, and hairy while its leaves are mainly alternate, long-stalked, mostly toothed, and egg-shaped or broader (http://montana.plant-life.org). The cultivated sunflower has a single flower head that averages between 0.25 to 0.5 feet wide, with yellow rays and a flat, dark disk (wisplants.uwsp.edu).
Each flower head can have 1,000 to 4,000 individual florets that are arranged in spiral whorls originating at the center of the inflorescence and grow progressively from the outer to the center of the disk (Weiss, 1983). The whorls follow a numerical pattern called the Fibonacci Number, or the Golden Ratio (Mathai & Davis, 1974 c.f. Weiss, 1983). The flowers are protandrous, which means the anthers mature before the stigma is receptive (Weiss, 1983). Also, the sunflower is self-incompatible, so it must be cross-fertilized (Harris & Hillman, 1989). Insects pollinate the sunflower, with the honeybee as its major pollinator. The fruit most commonly known as the “sunflower seed” is actually an achene, and it is grown in a variety of colors, including black, white, brown, striped, and mottled. These seeds vary in size and weight, but they generally appear compressed, flat, and oblong, with a truncated top and pointed base (Weiss, 1983). Seeds are ready to harvest when the back of the flower heads turn a yellow or brown color. They are usually threshed directly or thrown into a harvester. Threshed sunflower heads are burnt or plowed in after harvest, but they are also sometimes ground up and fed to animals (Weiss, 1983).
There are no special requirements when it comes to cultivating sunflowers, for which cultivation practices used for maize or wheat are adequate. Deep or chisel plowing is necessary to break up impacted soil layers because it allows for unrestricted root development (Weiss, 1983). The sunflower blooms during the summer (www.ces.ncsu.edu).
The sunflower seed is a good source of protein, fat, and carbohydrates. Naturally, because it is an oilseed crop, it also contains 25 to 35% oil, but Russian cultivars can have up to 50% oil content. The oil contains 44 to 72% linoleic acid and 13 to 20% protein. Stems and husks are rich in potash. The flowers themselves contain 12.7% protein, 13.7% fat, 64.3% total carbohydrate, 32.9 g of fiber, 9.3 g o f ash, 630 mg of calcium, and 80 mg phosphorus per 100 grams (hort.purdue.edu).
The sunflower is cultivated mostly for its seed, which is the world’s second most valuable source of edible oil. Sunflower oil is used for cooking, margarine, salad dressings, lubrication, soaps, and illumination. It is also used in paints and varnishes. Sunflower is used to feed livestock, but kernels are also eaten by humans raw, roasted, salted, or as flour. The flowers yield a yellow dye. The plants can be used for fodder, silage, and green manure (hort.purdue.edu).
Though its center of domestication is still being debated, there is no question that the sunflower is widely dispersed. The sunflower is a highly adaptable crop. The current major producers of sunflower include the European Union, Ukraine, China, India, Turkey, South Africa, and Argentina (National Sunflower Association, 2011).
Review and Discussion of Current Data on the Origin of Sunflower
The majority of older literature favors North America as the center of domestication for H. annuus, but more recent research explores the possibility that Mexico is the center of origin for the domesticated sunflower. In fact, various examples of linguistic, archaeological, and historical evidence support the hypothesis that the area of origin and domestication for the sunflower may be found particularly in Mexico and not central and eastern United States.
The yellow rays of the sunflower are indicative of its genus name because Helianthus is derived from two Greek words, one being Helios, which means “sun,” and the other being anthos, which means “flower” (wisplants.uwsp.edu, Gonzalez-Perez & Vereijken, 2007). The Spanish name for sunflower is “girasol,” while the French name is “tournesol,” which means to “turn with the sun,” a behavior that is characteristic of the sunflower (Gonzalez-Perez & Vereijken, 2007).
Historical and linguistic records suggest that the sunflower has been known in Mexico from as early as 1591. In that year, Joseph de Acosta, a Spanish sixteenth-century Jesuit missionary and naturalist in Latin America, listed the sunflower as “la flor que llaman del sol” in his book Historia Natural. In 1890, Bernabe Cobo, another Spanish Jesuit missionary and writer, mentioned the “tornasol,” which appears to be spelled similarly to the French term “tournesol,” in his Historia del Nuevo Mundo.
Researchers P. C. Mangelsdorf and R. G. Reeves argued that the sunflower was not known in Mexico in earlier times. They claimed that, “the sunflower is known today only in northern Mexico and known by the name ‘maize de teja’ which indicates that it was introduced from elsewhere, and after corn was already there” (Mangelsdorf & Reeves, 1939 c.f. Heiser Jr., 1951). In response to this hypothesis, Heiser Jr. (1942) pointed out that in Francisco Hernandez’s book Historia de las Plantas de Nueva Espana, the sunflower was known as “chimalacatl” and “anthillion,” terms not derived from the word “maize.”
In contrast, in their 2008 paper “Sunflower (Helianthus annuus L.) as a Pre-Columbian Domesticate in Mexico,” David Lentz and his associates proposed that if a domesticated plant were borrowed from another culture, a phonetic resemblance would be found in the borrower’s name for the plant. They further ventured the possibility that if an indigenous culture had a unique name for a plant with no phonetic similarity to the Spanish terms and had traditions associated with the plant, then a long history of use of the plant was implied (Lentz et al., 2008). After applying this theory to the terms used by different Mesoamerican and North American groups in regards to the sunflower, they found that of the 14 groups of indigenous people interviewed about their traditional knowledge of the sunflower, 11 groups had unique names for the sunflower that did not resemble the Spanish terms “girasol” and “mirasol” (Lentz et al., 2008).
Lentz and his associates discovered something interesting about the use of the sunflower among the Nahua indigenous Mexican group, known descendants of the Aztecs. The Nahua informants revealed that the sunflower was used as an ornament in churches or as a funeral offering in the cemetery. They called the sunflower two different names: “chimalacatl,” meaning shield reed, and “chimalxochitl,” meaning shield flower (Lentz et al., 2008). According to Lentz et al. (2008), the names refer respectively to the hollow sunflower stems and the large, disk-like head of the sunflower. Also, the “shield” part of the Nahua name refers to “prominent pre-Columbian armament … that became obsolete after the Conquest” (Lentz et al., 2008). After exploring the connection between the Nahua name and the early Spanish observation of the presence of the sunflower in central Mexico and its cultural and spiritual influence on the people, Lentz et al. concluded that the Nahua’s version of the sunflower name was probably developed before 1492, the year Christopher Columbus arrived in the Americas (Lentz et al., 2008).
The paper also explored the Otomi term “da nakhua,” which means “big flower that looks at the sun god” (Lentz et al., 2008). Lentz et al. made a connection between the term and pre-Columbian solar worship. They also referenced observations made by anthropologist James Dow, who noticed that Otomi crosses were decorated with sunflowers, making them look more like the pre-Columbian cross rather than the traditional Christian cross (Dow, 2003 c.f. Lentz et al, 2008).
After examining linguistic evidence from languages of Greek, Spanish, French, North American native Indian, and indigenous Mexican descent, I conclude that the origin of domestication for the sunflower is most likely somewhere in Mexico. The differences in sunflower terminology among indigenous Mexican groups in comparison to Spanish terminology illustrate that the Spanish had minimal influence in the Mexican names for the sunflower. The evidence also supports the hypothesis that the sunflower existed in Mexico prior to the arrival of the Spanish.
Documented observations and history of use strengthens the argument that the domesticated sunflower originated in Mexico. Also, Lentz et al. (2008) provided a testable hypothesis, used the reliable method of interviewing indigenous people with traditional knowledge of the sunflower, and found a correlation between the terminology and pre-Columbian behaviors such as religious or spiritual ceremonies. Linguistic evidence therefore strongly supports Lentz et al.’s (2008) hypothesis that Mexico is the center of domestication of the sunflower; however, it does not exclude the possibility that the sunflower was domesticated in the eastern U.S. and then dispersed during pre-Columbian times to Mesoamerica.
Though linguistics provide a reasonable argument for the original site of domestication for the sunflower, specific archaeological discoveries provide physical proof that Mexico is the most likely center of origin. It had been popularly believed that the sunflower was native to North America (www.hort.purdue.edu). The earliest remains of domesticated sunflowers were originally thought to be from Arizona and dated from 1000 cal B.C. (Fritz, 1990 c.f. Sauer, 1994). According to Harter et al. (2004), archaeological evidence was also reported at multiple sites in what are now Tennessee, Kentucky, Iowa, Arkansas and Ohio; specific examples of these archaeological sites include the Higgs site in Tennessee (Brewer, 1973 c.f. Harris & Hillman, 1989) and the Marble Bluff shelter in Arkansas (Fritz, 1986 c.f. Harris & Hillman, 1989).
In 2001, however, Kevin O. Pope and his team of researchers discovered domesticated sunflower remains at a San Andres site in Tabasco, Mexico. The remains consisted of a carbonized sunflower seed and partially carbonized achene that had been well preserved in waterlogged conditions (Pope, 2001 c.f. Lentz et al., 2001). The remains were discovered in strata considered to be of “Late Archaic” age. Accelerated mass spectrometry readings of this sunflower seed indicate a radiocarbon date of 4130 + B.P. or 2872 to 2575 cal B.C., while the achenes produce a radiocarbon date of 4085 + 50 B.P. or 2867 to 2482 cal B.C. Lentz and his associates provided radiocarbon dates for deeper strata and confirmed that they were older than the strata from which they excavated the domesticated sunflower plant remains (Lentz et al, 2001).
According to the criteria of seed size, there is no doubt that the San Andres discoveries come from a domesticated sunflower plant. Consequences of the domestication of the sunflower include larger achene size, enlarged floral disk, and suppression of lateral flowers in favor of one central head (or monocephaly) (Heiser, 1985 c.f. Lentz et al., 2001). The carbonized sunflower seed was 8.2 mm in length and 4.5 mm in width; though it is small in comparison to modern seeds, Lentz and his associates (2001) are certain it is “too large to be considered anything but from a domesticated plant.” The partially carbonized achene was 7.8 mm long and 4.4 mm wide, which they argue is within the domestication range (Lentz et al., 2001). The domestication range for seed size is usually between 10 and 25 mm in length, 7.5 to 15 mm wide, and 3 to 7.5 mm thick (Weiss, 1983).
The San Andres discovery is not an isolated event; archaeological expeditions in both Mexico and North America have uncovered wild and domesticated sunflower remains. Plant remains of wild sunflowers were found in Ocampo, Mexico and from the Napoleon Hollow site in Illinois (Callen, 1969, Ash & Ash, 1985 c.f. Lentz et al., 2001); radiocarbon dates for those sites are 2900 to 2200 cal B.C. and 2834 to 2074 cal B.C. respectively. In 1993, six carbonized sunflower seeds were found at the Hayes site in Tennessee and were dated between 3023 and 2666 cal B.C. (Lentz et al., 2001); though Crites (1993) reported that the seeds were from a domesticated sunflower, their size (6.9 mm) falls within the wild population range and does not meet domestication range criteria.
Lentz et al. point out that domesticated sunflower remains found in North America only date back to the late second millennium B.C. They cite the remains found at the Marble Bluff site in northern Arkansas (1264 to 912 cal B.C.), which are chronologically closer in age to those found at the Higgs site in eastern Tennessee (1259 to 829 cal B.C.) (Lentz et al., 2001). This showcases the glaring difference in radiocarbon dates of North American sunflower plant remains and those found in Mexico.
A domesticated sunflower achene was also discovered at a Santa Leticia site in western El Salvador and dated at 400 B.C. to 250 A.D. (Lentz et al., 2008). In Lentz et al.’s 2008 paper, they report a third discovery of domesticated sunflower remains in Mexico, specifically three large achenes found in a dry cave in Cueva del Gallo, Mexico (Lentz et al., 2008). These three separate discoveries of domesticated sunflower remains in Mexico contest the long-accepted belief that the sunflower was domesticated in North America.
Yet recently published journal articles by Charles B. Heiser threaten the validity of Lentz et al.’s argument and the authenticity of the San Andres domesticated sunflower plant remains. Heiser (2007) claims the specimen recovered from the San Andres archaeological site was not from a domesticated sunflower, as Lentz et al. states, but rather that it was most likely the seed of the Lagenaria siceraria or the bottle gourd. He believes the supposed domesticated sunflower achene falls into the range of morphological variability of the bottle gourd. He references Hart et al.’s (2004) molecular study and Smith’s (2006) morphological study of the achene, as well as his own 2002 paper, in which he came to the conclusion there was a lack of domesticated sunflowers in the early history of Mexico (Heiser, 2007).
Radiocarbon dating is a reliable method used by archaeologists to date material preserved in deposits. The radiocarbon dates given to the San Andres “domesticated sunflower” seed and achene were remarkably older than those found in archaeological sites in central and eastern United States. Older radiocarbon dates make Mexico a possible center of domestication of the sunflower. However, Heiser’s recent remarks undermine Lentz et al.’s hypothesis that the center of origin and domestication of the sunflower is in Mexico. Unfortunately, the San Andres plant remains were destroyed in the process of radiocarbon dating and therefore cannot be re-examined to support or deny Heiser’s claims.
Whether the domesticated sunflower is originally from North America or Mexico, the fact remains that it was an Indian crop, although a minor one, in both areas during Pre-Columbian times. Therefore, when the Europeans arrived in North America, it was already under cultivation (Sauer, 1994; Weiss, 1938). By 1568, many years after Christopher Columbus’s arrival in the Americas, the sunflower also started appearing in European herbals (Sauer, 1994). The sunflower appeared in Spain in 1568 and Belgium in 1576 (Heiser Jr., 1951). It had reached both Italy and Germany by 1623 (Heiser Jr., 1951).
In a 2007 review of sunflower proteins, Sergio Gonzalez-Perez and Johan Vereijken claim that the sunflower was a common crop among North American Indian tribes and present in Arizona and New Mexico around 3000 B.C. They also noted that a Spanish explorer named Nicolas Bautista Monardes brought the domesticated sunflower to Europe in 1569, and that later Tsar Peter the Great had it transported to Russia (Gonzalez-Perez & Vereijken, 2007).
Charles B. Heiser offers an alternative theory of how the domesticated sunflower reached Europe in his 1998 paper titled “The Domesticated Sunflower in Old Mexico?” He concludes that there was a lack of evidence proving that the sunflower was in Mexico in early historical times and suggested that the origin of domestication was from the region of what is now central or eastern United States (Heiser, 1998). He also withdraws the ideas he supported in his 1951 paper, which included the belief that the monocephalic domestic sunflower was known in Mexico in Pre-Columbian times. In the 1951 paper, he references the work of Francisco Hernandez, a naturalist and court physician to the King of Spain in the sixteenth century. In the 1998 paper, Heiser writes, “At the time I thought Francisco Hernandez had seen the sunflower in Mexico in his sojourn there between 1570 and 1577 … From a restudy of his works recently, however, I have decided that he did not observe the sunflower in Mexico.” Heiser (1998), however, clarifies that though Hernandez did not observe the sunflower in Mexico, “it does not necessarily follow that the sunflower was not present in that country at the time of his visit.” His paper effectively attempts to rule out Mexico as the origin of domestication. In the same paper, he also declares that the sunflower probably did not reach Europe from Mexico, but rather that it was introduced to Europe by Hernando de Soto, a Spanish explorer and conquistador, after his expedition to southeastern United States, which lasted from 1539 to 1543 (Heiser, 1998).
Despite the disagreements over where the sunflower was domesticated and which Spanish explorer introduced it to Europe, one factor is generally agreed upon: Europeans embraced the sunflower. Its popularity rose, and it quickly became a favored ornamental in European countries. In the early eighteenth-century, the British suggested that it could become an oilseed crop; by the late nineteenth century, Russians were breeding sunflowers to increase their seed oil content, seed size, and flower head size. In the early 20th century, H. annuus was the most valuable oilseed crop in Europe, with the Soviet Union as its leading producer.
The sunflower was re-introduced by immigrants to North America in the late 19th century and eventually became popular in home gardens; according to Weiss (1983), the reintroduction in the late 19th century explains the differences between eastern and western species that exist in North America. Sunflower production in North America, specifically in the Dakotas and Minnesota, started again in the 1970s, and now sunflower seeds are produced by the millions of tons annually in the United States, ranking second only to soybeans as a vegetable oil crop (Sauer, 1994). The sunflower is also a major crop internationally; for example, by 1970, Australia had begun planting sunflowers on a major scale. Since then, H. annuus has also become a major crop in Spain (Beard, 1981 c.f. Sauer, 1994).
Other researchers have claimed different pre-Columbian centers of domestication, but the lack of substantial evidence rules out their hypotheses. For example, in 1568, Rembertus Dodonaeus, a Flemish physician and botanist, believed Peru was the area of origin of the sunflower; at the time, the sunflower was known as chrysanthemum peruvianum (Heiser Jr., 1951). Alexander de Humboldt, a German naturalist and explorer, supported Dodonaeus’s claims in 1918, stating, “the chimalatl, or sun with the large flowers (H. annuus) came from Peru to New Spain (Heiser Jr., 1951). Charles Heiser Jr. clarifies this Peru confusion in his 1951 paper when he states “The assignment of plants to ‘Peru’ in the early herbals cannot always be taken literally, but [is] simply an indication that the plant came from somewhere in the Americas.”
Recommended Future Lines of Research
The majority of older literature concludes that North America, most specifically central and eastern United States, is the origin of domestication of the sunflower, but recent research shows that Mexico may be a more viable candidate. However, advocates of the domesticated sunflower’s North American descent have responded to the calls of critics such as David Lentz.
Charles B. Heiser’s most recent articles hint at the type of future research that must be done to settle this debate. Because the supposed domesticated sunflower plant remains may be degraded or otherwise unavailable for further observation, I suggest looking at other types of evidence that already exists, such as linguistic, historical, botanical, and genetic data.
Comparing sunflower terminology between the indigenous groups of Mexico and North America, the Spanish explorers, and the European countries may indicate which region most influences the Spanish and European cultures, which can then point to the center of origin of the sunflower. Following historical records of which Spanish explorers introduced the sunflower to Europe, or more specifically the region from which they took the sunflower plant, may also indicate the center of origin of the sunflower. Comparing botanical data of certain wild sunflowers and the domesticated sunflowers may highlight similarities between varieties and determine where the highest diversity can be found. Examining genetic data via RAPD analysis, gel electrophoresis, and other techniques can form genetic maps that may be compared to geographic maps so that wherever the earliest domesticated sunflower was found may suggest the proper center of domestication. If archaeological evidence is damaged and no longer useful for these genetic data tests, researchers can reference the results and work of their predecessors. Researchers may take any of these approaches in further studying the mystery of the sunflower’s original domestication. Whether or not it is still North America’s only domesticate, it is imperative that researchers focus their attention on this valuable oilseed crop.
Crites, G. D. 1993. Domesticated Sunflower in Fifth Millenium B.P. Temporal Context: New Evidence from Middle Tennessee. American Antiquity. 58(1): 146-148. Accessed via JSTOR database. Accessed 23 April 2011.
Gonzalez-Perez, S., Vereiken, J. 2007. Sunflower proteins: overview of their physicochemical, structural and functional properties. Journal of the Science of Food and Agriculture. 87: 2173-2191. Accessed via BIOSIS database. Accessed 7 April 2011.
Harris, David R., and Gordon C. Hillman. Foraging and Farming: the Evolution of Plant Exploitation. London: Unwin Hyman, 1989.
Harter, A.V., Gardner, K. A., Falush, D., Lentz, D. L., Bye, R. A., Rieseberg, L. H. 2004. Origin of extant domesticated sunflowers in eastern North America. Nature. 430 (6996): 201-205. Accessed via BIOSIS database. Accessed 24 April 2011.
Heiser Jr., Charles B. 1951. The Sunflower among the North American Indians. Proceedings of the American Philosophical Society. 95(4): 432-448. Accessed via JSTOR database. Accessed 24 April 2011.
Hesier, Charles B. 1998. The domesticated sunflower in old Mexico? Genetic Resources and Crop Evolution. 45: 447-449. Accessed via JSTOR database. Accessed 25 May 2011.
Heiser, Charles B. 2007. The sunflower (Helianthus annuus) in Mexico: further evidence for a North American domestication. Genetic Resources and Crop Evolution. 55: 9-13. Accessed via JSTOR database. Accessed 25 May 2011.
Lentz, D., Pohl, M., Pope, K., Wyatt, A. 2001. Prehistoric Sunflower (Helianthus annuus L.) Domestication in Mexico. Economic Botany. 55(3): 370-376. Accessed via JSTOR database. Accessed 23 April 2011.
Lentz, D., Pohl, M., Alvarado, J. L., Tarigaht, S., Bye, R. 2008. Sunflower (Helianthus annuus L.) as Pre-Columbian Domesticate in Mexico. Proceedings of the National Academy of Sciences of the United States of America. 107(17): 6232-6237. Accessed via JSTOR database. Accessed 23 April 2011.
Montana Plant Life. <http://montana.plant-life.org>. Accessed 21 May 2011.
National Sunflower Association. <http://www.sunflowernse.com>. Accessed 21 May 2011.
North Carolina Cooperative Extension. <www.ces.ncsu.edu>. Accessed 25 May 2011. Plant Database - Sunflower: <plants.usda.gov>. Accessed 21 May 2011.
Purdue University Agriculture. <www.hort.purdue.edu>. Accessed 21 May 2011.
Sauer, Jonathon D. Historical Geography of Crop Plants: A Select Roster. Florida: CRC Press, 1994.
University of Wisconsin. <wisplants.uwsp.edu>. Accessed 21 May 2011.
Weiss, E. A. Oilseed crops. Longman Group Ltd, New York, 1983.