Four Corners potato previously unknown part of ancient human diet
- Source: University of Utah
- Summary:
- Potato starch residues have been discovered in the
crevices of a 10,900-year-old stone tool in Escalante, Utah -- the
earliest evidence of wild potato use in North America. This is the first
archaeological study to identify Solanum jamesii, a wild species native
to the southwestern United States, as an important part of ancient
human diets. The long history could mean that the species was
transported, cultivated or even domesticated.
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FULL STORY
Louderback holds the tiny tubers
of S. Jamesii, the Four Corners potato. U researchers discovered the
spud's starch residues in the crevices of a 10,900-year-old stone tool
in Escalante, Utah -- the earliest evidence of wild potato use in North
America.
Credit: University of Utah
The town of Escalante in southern Utah
is no small potatoes when it comes to scientific discovery; a new
archaeological finding within its borders may rewrite the story of tuber
domestication.
Researchers from the Natural History Museum of Utah and Red Butte
Garden at the University of Utah have discovered potato starch residues
in the crevices of a 10,900-year-old stone tool in Escalante, Utah --
the earliest evidence of wild potato use in North America. This is the
first archaeological study to identify a spud-bearing species native to
the southwestern United States, Solanum jamesii, as an
important part of ancient human diets. The researchers pieced together
evidence from stone tools, ethnographic literature and modern gardeners
to show that Utahans have used the species intermittently for over
10,000 years. The Escalante area was even previously known as "Potato
Valley" to early settlers.
Several Native American tribes, including Apache, Hopi, Kawaik, Navajo, Southern Paiute, Tewa, Zia and Zuni, consumed S. jamesii.
The groups used various cooking and processing techniques, including
boiling the potatoes, grinding them into flour or yeast, and mixing the
potatoes with clay to reduce bitterness. Some groups still tend their
potato populations in cultivated gardens.
The long history could mean that the species was transported, cultivated or even domesticated. If true, S. jamesii
would be the first example of a plant domesticated in the western U.S.
To find out, the researchers are collaborating with geneticists from the
United States Department of Agriculture, who are mining S. jamesii's DNA for genes resistant to drought and disease that could help diversify current potato crops to be more resilient.
"This potato could be just as important as those we eat today not
only in terms of a food plant from the past, but as a potential food
source for the future," says Lisbeth Louderback, senior author of the
study that published online July 3 in the Proceedings of the National Academy of Sciences.
"The potato has become a forgotten part of Escalante's history. Our
work is to help rediscover this heritage." Louderback is an assistant
professor of anthropology at the U and curator of archeology at the
Natural History Museum of Utah.
S. tuberosum vs S. jamesii
The potatoes we buy at the grocery store are all varieties of a
single species, Solanum tuberosum, that was domesticated in the South
American Andes more than 7,000 years ago. Since then, S. tuberosum has
diversified into the reds, russets and thousands of other potato types
for sale in markets around the world.
The new study deals with S. jamesii, a wild species found in
the shady shelter of oaks, sagebrush and piñon pines across the Four
Corners region of the southwestern U.S. The so-called Four Corners
potato is most abundant in the highlands of New Mexico, where its green
leaves and delicate white flowers are scattered throughout piñon-juniper
woodlands. In Utah, however, the plants only grow in sparse, isolated
populations near archaeological sites, suggesting that ancient people
carried the tubers to the area. Only five small populations of plants
are known in the Escalante Valley, including one just 150 meters from
the archaeological site, North Creek Shelter. The researchers have
enlisted the Escalante community to help conserve the plants and
preserve their cultural heritage.
"It's hard to persuade the general public to care about rare plants.
But this one has a real history associated with native people, with
pioneers, with folks living though the depression and with the residents
in Escalante today," says Bruce Pavlik, director of conservation at Red
Butte Garden and co-author of the study. "Across the range, it really
should be treated as an antiquity, in a sense."
Manos and metates: ancient food processors
Louderback analyzed stone tools from North Creek Shelter in the
Escalante Valley, one of Utah's oldest archaeological sites with an
11,000-year history. Its residents were mostly hunters and gatherers
until the Fremont and Ancestral Puebloan cultures arrived and began
cultivating crops. Today, the Southern Paiute inhabit this region along
with descendants of Mormon settlers.
Archaeologists use mathematical models derived from foraging theory
to describe how and why people foraged for food resources. Using what is
called the diet breadth model, archaeologists rank dietary animals and
plants according to their energy content and the effort required to
harvest and process the food. The discovery of S. jamesii
consumption adds a new energy source that has been largely ignored in
ancient diets, partly because tubers don't preserve well in
archaeological deposits. Unlike animal bones and corn cobs, tubers are
composed of soft tissues that disintegrate easily. Yet they pack a
caloric punch, and are important for understanding ancient peoples' way
of life.
Louderback examined large sandstone slabs called metates and handheld
grinding stones called manos, the ancient food processors on which
people prepared meals. She found microscopic starch granules that
previous archaeologists never suspected were present.
"Grinding plant tissues with manos and metates releases granules that
get lodged in the tiny cracks of stone, preserving them for thousands
of years. Archaeologists can retrieve them using chemicals, modern
microscopy and advanced imaging techniques," says Louderback.
All starch granules have concentric circles that grow outward like
tree rings. The origin of growth begins with what's called the hilum.
The majority of plant species have starch granules with hila at the
center of the grain. However, the hila of granules filling Louderback's
microscope slides were off-center. Only a few species from the Four
Corners region produce starch granules with that specific
characteristic; S. jamesii is one of them.
She and NHMU postdoctoral research associate Nicole Herzog, now a
lecturer at Boise State University, analyzed granules from modern-day S. jamesii
to establish a set of five characteristics that accurately identified
the wild potato, starting with the off-center hilum. Starch granules
with five out of five characteristics were a verified wild potato. They
analyzed tubers from three different modern populations, 100 granules
per tuber.
Louderback and Pavlik checked for the characteristics on granules
found on the ancient stone tools from North Creek Shelter. Out of the
323 total starch granules, 122 had the off-center hilum. Of those, nine
were verified S. jamesii and another 61 were either likely or possibly S. jamesii.
The future of the Four Corners potato
The researchers are collaborating with colleagues from the USDA Potato Genebank, who have studied the genetics of S. jamesii
since the 1990s. Future efforts will focus on understanding patterns of
genetic diversity across the Four Corners region to look for clues
about whether it was transported, manipulated or even domesticated.
The researchers want to make the potatoes available for the Escalante
community to grow in their gardens to help with conservation. But
first, they need to untangle the mysterious ecology of the potato in the
wild -- its pollinators and conditions necessary for sexual
reproduction are still unknown.
"We are working with the people of Escalante to bring awareness to
this valuable resource and show them what the species looks like, where
it grows, its tremendous history and enlist their help as stewards of
the Four Corners potato," says Pavlik.
