Nav: Home

Maize from El Gigante Rock Shelter shows early transition to staple crop

August 07, 2017

Mid-summer corn on the cob is everywhere, but where did it all come from and how did it get to be the big, sweet, yellow ears we eat today? Some of the answers come from carbon dating ancient maize and other organic material from the El Gigante rock shelter in Honduras, according to a team of anthropologists who show that 4,300 years ago maize was sufficiently domesticated to serve as a staple crop in the Honduran highlands.

"Staple crops provide the basis for the development of many complex societies around the world that started developing after about 5,000 years ago," said Douglas J. Kennett, head and professor of anthropology, Penn State. "They are associated with a complete commitment to agriculture."

Maize, or corn in North America, is an important food and fuel crop. The evolutionary history of such a staple is important and archaeological sites with well-preserved maize are incredibly rare, according to Kennett.

The abundance of artifacts and the exceptionally good preservation in the rock shelter that sits on the western escarpment of the Estanzuela River in the highlands of western Honduras make it an ideal site to explore domestication of maize and its transition into a staple crop in the New World. High-precision accelerator mass spectrometry -- radiocarbon dating -- allowed a precise chronology to be determined for the organic remains found in the rock shelter.

"When you walk across the surface of the rock shelter, the floor is covered with corn cobs and lithics," said Ken Hirth, professor of anthropology, Penn State. "We have about 10,000 pieces of maize plants and 1,000 cobs from the site."

Most researchers agree that maize evolved from the teosinte plant somewhere in the Balsas area of the southwestern region of Mexico and appeared around 9,000 years ago. But the original maize cobs had few rows and kernels.

"The maize in El Gigante is interesting because of how large it gets very quickly," said Hirth. "Something is going on in the margins of the area. These cobs are bigger than those known from other areas of Mexico for the same time period."

While a type of teosinte exists in the area of El Gigante, it is not one that hybridizes with maize.

"We hypothesize that the domestication history of maize in Honduras is distinct from Mexico because Honduras is well outside the range of the wild plant that maize was domesticated from," said Kennett. "There is known introgression (hybridization and backcrossing) between teosinte and maize and this could have slowed the domestication process in Mexico."

According to Kennett, based on the small cobs from Mexico, researchers thought that the transition to more complex societies in Mesoamerica 4,000 years ago occurred before maize was a fully domesticated staple crop.

Data from El Gigante now suggests that maize in some parts of Mesoamerica was productive enough to be a staple 4,300 years ago, the researchers report in today's (Aug 7) issue of Proceedings of the National Academy of Sciences.

The researchers radiocarbon dated 88 samples of botanical material from El Gigante, creating a statistical chronology over the past 11,000 years. They directly dated 37 cobs that showed the earliest cobs with 10 to 14 rows, a higher number than typically found in Mexico at this time. Dated cobs from 2,360 to 980 years ago were similar, but had larger cobs and kernels and more rows.

Logan Kistler, a researcher at the Smithsonian Institution and a coauthor on this paper, is currently working with the team on an ancient DNA study to determine if the earliest El Gigante maize was fully domesticated. Recent studies on cobs from the Tehuacan Valley dating to approximately 5,300 years ago -- 1,000 years older than the El Gigante cobs -- indicate that those plants were only partially domesticated.

The researchers also are now looking at the diversification of maize at El Gigante in later time periods.
-end-
Working on the project from Penn State are David L Webster, professor emeritus of anthropology; Brendon J. Culleton, research associate in anthropology; and Thomas K. Harper, research assistant. Also on the project are Heather B. Thakar, curator of anthropological research collections, Texas A&M University; Amber VanDerwarker, professor of anthropology, University of California, Santa Barbara; and Timothy E. Scheffler, lecturer, University of Hawaii, Hilo. The National Science Foundation supported this work.

Penn State

Related Maize Articles:

Detailed new genome for maize shows the plant has deep resources for continued adaptation
A much more detailed reference genome for maize is published in Nature today.
Corn with a cover of grass
Corn raised for biofuel can result in eroded soils, as all materials are removed from the field.
Geography and culture may shape Latin American and Caribbean maize
Variations in Latin American and Caribbean maize populations may be linked to anthropological events such as migration and agriculture, according to a study published April 12, 2017 in the open-access journal PLOS ONE by Claudia Bedoya from the International Maize and Wheat Improvement Center (CIMMYT) and colleagues.
New plant research leads to discovery of a gene that increases seed yield in maize
Researchers from VIB-UGent have discovered a gene that significantly increases plant growth and seed yield in maize.
Maize study finds genes that help crops adapt to change
A new study analyzed close to 4,500 maize varieties to identify more than 1,000 genes driving large-scale adaptation to the environment.
Mutant maize offers key to understanding plant growth
New findings by a University of California, Riverside-led team of researchers, lend support to the second idea, that the orientation of cell division is critical for overall plant growth.
DNA study unravels the history of the world's most produced cereal
Genome sequence of a 5,310-year-old maize cob provides new insights into the early stages of maize domestication.
DNA evidence from 5,310-year-old corn cob fills gaps in history
Researchers who have sequenced the genome of a 5,310-year-old corn cob have discovered that the maize grown in central Mexico all those years ago was genetically more similar to modern maize than to its wild ancestor.
Vitamin A orange maize improves night vision
A new study has found that vitamin A-biofortified orange maize significantly improves visual functions in children.
Soil management may help stabilize maize yield in the face of climate change
Given that predicted climate changes are expected to affect maize yields, many researchers and companies are focusing on improving maize varieties to withstand more stressful environments.

Related Maize Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Climate Crisis
There's no greater threat to humanity than climate change. What can we do to stop the worst consequences? This hour, TED speakers explore how we can save our planet and whether we can do it in time. Guests include climate activist Greta Thunberg, chemical engineer Jennifer Wilcox, research scientist Sean Davis, food innovator Bruce Friedrich, and psychologist Per Espen Stoknes.
Now Playing: Science for the People

#527 Honey I CRISPR'd the Kids
This week we're coming to you from Awesome Con in Washington, D.C. There, host Bethany Brookshire led a panel of three amazing guests to talk about the promise and perils of CRISPR, and what happens now that CRISPR babies have (maybe?) been born. Featuring science writer Tina Saey, molecular biologist Anne Simon, and bioethicist Alan Regenberg. A Nobel Prize winner argues banning CRISPR babies won’t work Geneticists push for a 5-year global ban on gene-edited babies A CRISPR spin-off causes unintended typos in DNA News of the first gene-edited babies ignited a firestorm The researcher who created CRISPR twins defends...