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Different varieties of sweet potato on display at the International Potato Center in Lima, Peru. The sweet potato originated in the Americas and spread across the globe. Robert Scotland

Many botanists argued that humans must have carried the valuable staple to the Pacific from South America. Not so, according to a new study.

Carl Zimmer APRIL 12, 2018

Nytimes.com

Of all the plants that humanity has turned into crops, none is more puzzling than the sweet potato. Indigenous people of Central and South America grew it on farms for generations, and Europeans discovered it when Christopher Columbus arrived in the Caribbean.

In the 18th century, however, Captain Cook stumbled across sweet potatoes again — over 4,000 miles away, on remote Polynesian islands. European explorers later found them elsewhere in the Pacific, from Hawaii to New Guinea.

The distribution of the plant baffled scientists. How could sweet potatoes arise from a wild ancestor and then wind up scattered across such a wide range? Was it possible that unknown explorers carried it from South America to countless Pacific islands?

An extensive analysis of sweet potato DNA, published on Thursday in Current Biology, comes to a controversial conclusion: Humans had nothing to do with it. The bulky sweet potato spread across the globe long before humans could have played a part — it’s a natural traveler.

Some agricultural experts are skeptical. “This paper does not settle the matter,” said Logan J. Kistler, the curator of archaeogenomics and archaeobotany at the Smithsonian Institution.

Alternative explanations remain on the table, because the new study didn’t provide enough evidence for exactly where sweet potatoes were first domesticated and when they arrived in the Pacific. “We still don’t have a smoking gun,” Dr. Kistler said.

The sweet potato, Ipomoea batatas, is one of the most valuable crops in the world, providing more nutrients per farmed acre than any other staple. It has sustained human communities for centuries. (In North America, it often is referred to as a yam; in fact, yams are a different species originating in Africa and Asia.)

Scientists have offered a number of theories to explain the wide distribution of I. batatas. Some scholars proposed that all sweet potatoes originated in the Americas, and that after Columbus’s voyage, they were spread by Europeans to colonies such as the Philippines. Pacific Islanders acquired the crops from there.

As it turned out, though, Pacific Islanders had been growing the crop for generations by the time Europeans showed up. On one Polynesian island, archaeologists have found sweet potato remains dating back over 700 years.

A radically different hypothesis emerged: Pacific Islanders, masters of open-ocean navigation, picked up sweet potatoes by voyaging to the Americas, long before Columbus’s arrival there. The evidence included a suggestive coincidence: In Peru, some indigenous people call the sweet potato cumara. In New Zealand, it’s kumara.

A potential link between South America and the Pacific was the inspiration for Thor Heyerdahl’s famous 1947 voyage aboard the Kon-Tiki. He built a raft, which he then successfully sailed from Peru to the Easter Islands.

Genetic evidence only complicated the picture. Examining the plant’s DNA, some researchers concluded that sweet potatoes arose only once from a wild ancestor, while other studies indicated that it happened at two different points in history.

According to the latter studies, South Americans domesticated sweet potatoes, which were then acquired by Polynesians. Central Americans domesticated a second variety that later was picked up by Europeans.

Hoping to shed light on the mystery, a team of researchers recently undertook a new study — the biggest survey of sweet potato DNA yet. And they came to a very different conclusion.

“We find very clear evidence that sweet potatoes could arrive in the Pacific by natural means,” said Pablo Muñoz-Rodríguez, a botanist at the University of Oxford. He believes the wild plants traveled thousands of miles across the Pacific without any help from humans.

Mr. Muñoz-Rodríguez and his colleagues visited museums and herbariums around the world to take samples of sweet potato varieties and wild relatives. The researchers used powerful DNA-sequencing technology to gather more genetic material from the plants than possible in earlier studies.

Their research pointed to only one wild plant as the ancestor of all sweet potatoes. The closest wild relative is a weedy flower called Ipomoea trifida that grows around the Caribbean. Its pale purple flowers look a lot like those of the sweet potato.

Instead of a massive, tasty tuber, I. trifida grows only a pencil-thick root. “It’s nothing we could eat,” Mr. Muñoz-Rodríguez said.

The ancestors of sweet potatoes split from I. trifida at least 800,000 years ago, the scientists calculated. To investigate how they arrived in the Pacific, the team headed to the Natural History Museum in London.

The leaves of sweet potatoes that Captain Cook’s crew collected in Polynesia are stored in the museum’s cabinets. The researchers cut bits of the leaves and extracted DNA from them.

The Polynesian sweet potatoes turned out to be genetically unusual — “very different from anything else,” Mr. Muñoz-Rodríguez said.

The sweet potatoes found in Polynesia split off over 111,000 years ago from all other sweet potatoes the researchers studied. Yet humans arrived in New Guinea about 50,000 years ago, and only reached remote Pacific islands in the past few thousand years.

The age of Pacific sweet potatoes made it unlikely that any humans, Spanish or Pacific Islander, carried the species from the Americas, Mr. Muñoz-Rodríguez said.

Traditionally, researchers have been skeptical that a plant like a sweet potato could travel across thousands of miles of ocean. But in recent years, scientists have turned up signs that many plants have made the voyage, floating on the water or carried in bits by birds.

Even before the sweet potato made the journey, its wild relatives traveled the Pacific, the scientists found. One species, the Hawaiian moonflower, lives only in the dry forests of Hawaii — but its closest relatives all live in Mexico.

The scientists estimate that the Hawaiian moonflower separated from its relatives — and made its journey across the Pacific — over a million years ago.

But Tim P. Denham, an archaeologist at the Australian National University who was not involved in the study, found this scenario hard to swallow.

It would suggest that the wild ancestors of sweet potatoes spread across the Pacific and were then domesticated many times over — yet wound up looking the same every time. “This would seem unlikely,” he said.

Dr. Kistler argued that it was still possible that Pacific Islanders voyaged to South America and returned with the sweet potato.

A thousand years ago, they might have encountered many sweet potato varieties on the continent. When Europeans arrived in the 1500s, they likely wiped out much of the crop’s genetic diversity.

As a result, Dr. Kistler said, the surviving sweet potatoes of the Pacific only seem distantly related to the ones in the Americas. If the scientists had done the same study in 1500, Pacific sweet potatoes would have fit right in with other South American varieties.

Dr. Kistler was optimistic that the sweet potato debate would someday be settled. The world’s herbariums contain a vast number of varieties that have yet to be genetically tested.

“There are more than we could look at in a lifetime,” Dr. Kistler said.

For his part, Mr. Muñoz-Rodríguez plans on searching for more wild sweet potato relatives in Central America, hoping to get more clues to how exactly a thin-rooted weed gave rise to an invaluable crop.

Working out the history of crops like this could do more than satisfy our curiosity about the past. Wild plants hold a lot of genetic variants lost when people domesticated crops.

Researchers may find plants they can hybridize with domesticated sweet potatoes and other crops, endowing them with genes for resistance to diseases, or for withstanding climate change.

“Essentially, it’s preserving the gene pool that feeds the world,” Dr. Kistler said.

Caption1 The distribution of the sweet potato plant has baffled scientists. How could the plant arise from a wild ancestor in the Americas and wind up on islands across the Pacific? Karsten Moran for The New York Times

Caption2 Different varieties of sweet potato on display at the International Potato Center in Lima, Peru. The sweet potato originated in the Americas and spread across the globe. Robert Scotland

Link https://www.nytimes.com/2018/04/12/science/sweet-potato-pacific-dna.html

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field of Quinoa

 

Original Article

eurelalert.org

Archaeological remains found in southern Bolivia reveal a flourishing agrarian society from the 13th to the 15th centuries, despite marked drying and cooling of the climate throughout the period. This unexpected observation is the result of an interdisciplinary study conducted by an international team (CONICET, CNRS, IRD and UCSD). This research, published in Science Advances, highlights the adaptive capacity and resilience of societies with little hierarchical differentiation, in confronting the challenges of climate degradation.

Source: Unexpected agricultural production allowed pre-Hispanic society to flourish in arid Andes

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Amazonian farmers discovered how to manipulate wild rice so the plants could provide more food 4,000 years ago, long before Europeans colonized America, archaeologists have discovered.

Source: Amazon farmers discovered the secret of domesticating wild rice 4,000 years ago

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Original article:

NBC news.com
by Liam Miller
TEMUCO, Chile — Unearthed 1,000-year-old pottery remains could settle a bubbling debate and prove lager beer has its origins in South America.
Archaeologist Dr. Alberto Perez excavated ceramic pottery remains in southern forests near the Chile-Argentina border in 2016, just north of Patagonia.
A new genetic analysis of the ceramics has shown they contain traces of a yeast called Saccharomyces eubayanus — known as the “lost parent” of lager beer.
Perez’s find suggests that the group who made the ceramic vessels were probably using them to make a fermented drink from plant products, similar to the “chicha” or “mudai” beverage drunk in the region today. That might mean they were doing so using the yeast S. eubayanus to make alcohol more than 200 years before lager production began in Bavaria in the 1400s.
The discovery raises questions about whether South America is the origin of the unusual yeast that allows brewers to ferment lager at cool temperatures and provides its crisp and refreshing flavor.
“This is the first archaeological evidence and earliest evidence of any kind of Saccharomyces eubayanus being used in alcohol production,” said Perez, who is based at Universidad Catolica de Temuco in Chile. “Our findings confirm the historical presence of the yeast in this region and now we have confirmation of its use.”
Lager is the world’s most popular fermented drink and scientists have known since the 1980s that the yeast used to produce it — Saccharomyces pastorianus — is a hybrid between two “parent” yeasts.
One is a well-known warm-brewing yeast called Saccharomyces cerevisiae, used in making ales and bread.
But beer experts suspected the other cold-resistant parent did not come from Europe. Yeasts grow naturally in many places including skin fruits, trees, soil and even on insects. But one with the characteristics of S. eubayanus — which thrives in cold temperatures — has never been found growing wild in Europe.
The cold-resistant missing parent remained a secret until 2011 when Dr. Chris Hittinger from the University of Wisconsin-Madison and an international team of geneticists and microbiologists from the U.S., Portugal and Argentina identified S. eubayanus in wild samples from a Nothofagus tree in Patagonian forests.
The discovery was soon followed by a heated debate over a key qustion: How had a yeast from the cold southern regions of South America traveled to Bavaria where lager was invented in the 1400s — when European explorers only made landfall on South America in the late 1400s?
The timing appeared too tight. But some theorized the yeast might have traveled on the boat timber of the early traders who followed Christoper Columbus, or that early lagers had simply been brewed using different strains.
Following a 2014 discovery of wild-growing S. eubayanus on the Tibetan Plateau in western and northwestern China, a Chinese research paper led by Jian Bing and Pei-Jie Han argued that S. eubayanus more likely traveled from Asia on the Silk Road trade route, which was well established in time for lager’s invention.
New studies by Hittinger from 2014 until last year found S. eubayanus in several other locations including North America, while another group found isolates in New Zealand. And there were slightly varying types of S. eubayanus.

We discovered there were several strains of Saccharomyes eubayanus,” Hittinger said. “Our research showed that Patagonia is home to a tremendous diversity of S. eubayanus and one of our models suggested a lager yeast ancestor originated there and spread northwards.”
Yeasts migrate in a number of ways and Hittinger’s team proposed in their 2016 paper that birds or insects were a possible mode of transportation for S. eubayanus, possibly thousands of years before lager was invented and therefore in no need of a human helping-hand.
So how do Perez’s findings fit in?
“The evidence that Saccharomyces eubayanus may have been used to ferment beverages before contact between the Eastern and Western Hemispheres suggests an intriguing twist to the origin of lager yeasts,” said Hittinger, who was not part of Perez’s study. “Future genetic studies will be required to exclude the possibility that these strains are environmental contaminants and to determine how they are related to wild Patagonian strains, wild strains from the Northern Hemisphere, and the domesticated hybrid strains used to brew lagers.”
Perez’s team found the pottery remains near San Martin de Los Andes in Argentina, close to the Chilean border.
“The people who made them around 1,000 years ago would have been from a hunter-gatherer society with a mixed economy based on seasonal produce of mainly seeds and fruits and some cultivated plants,” he said.
His team excavated 6 of the 30 archaeological sites they identified in their survey, discovering and analyzing a large and diverse number of ceramic artifacts. Part of the analysis included making yeast cultures from organic residues extracted from inside the ceramics.
The analysis that led to the discovery of S. eubayanus was performed by an interdisciplinary team led by archaeologist Jose Luis Lanata and the biologist Christian Lopes, both based at Argentina’s National Scientific and Technical Research Council (CONICET).
“Saccharomyces eubayanus turned up in remains from two of the sites,” Perez said. “We had strong evidence showing the ceramics had been used to ferment vegetal products to produce alcoholic beverages.”
He speculated that these fermented drinks likely “played a prominent role in the spiritual and social world of the group.”

 

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 Findings may help illuminate understanding of plant domestication and cultivation in the Andes Mountains. Josue Hermoza, Wikimedia Commons

Findings may help illuminate understanding of plant domestication and cultivation in the Andes Mountains. Josue Hermoza, Wikimedia Commons

Original Article:

popular-archaeology.com

Researchers provide evidence for the early cultivation and use of potato (Solanum tuberosum) at an archaeological site in the Andes Mountains of south-central Peru. Studying the domestication of the potato, an important crop in the high Andes, could help illuminate the development of highland Andean culture, but limited direct botanical evidence of potato domestication in the region has hindered research efforts. Claudia Rumold and Mark Aldenderfer* collected microbotanical samples from groundstone tools from Jisakairumoko, a site situated in the western Titicaca Basin of Peru that reflects a transition from sedentism to food production. On 14 groundstone tools, the authors found 141 starch microremains, and microscope photographs and subsequent taxonomic identification revealed that 50 of the starch granules were of Solanum origin. The potato starches were similar in size to modern potato starches, and anthropogenic wear on the starches was consistent with culinary processing methods. The findings might help us understand the development of food production in Jisakaurumoko, and more broadly, illuminate plant domestication and cultivation in the Andes Mountains.

 

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oldest-beer-1-oba1

 

 

 

 

Yeast microbes from the world’s oldest bottle of beer — a 220-year-old bottle found in one of Australia’s earliest shipwrecks — are being used to create a new, modern beer with the characteristic taste of the 18th-century brew.

Source: Oldest Beer Brewed from Shipwrecks 220-Year-Old Yeast Microbes

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 Humans living in Argentina 14,000 years ago were hunting giant armadillos. This one looks especially grumpy.

Humans living in Argentina 14,000 years ago were hunting giant armadillos. This one looks especially grumpy.

 

Original Article:

By ANNALEE NEWITZ

arstechnica.com

 

A glimpse of the last people on Earth to colonize a continent without humans.

 

For more than a decade, evidence has been piling up that humans colonized the Americas thousands of years before the Clovis people. The Clovis, who are the early ancestors of today’s Native Americans, left abundant evidence of their lives behind in the form of tools and graves. But the mysterious pre-Clovis humans, who likely arrived 17,000 to 15,000 years ago, have left only a few dozen sources of evidence for their existence across the Americas, mostly at campsites where they processed animals during hunting trips. Now a fresh examination of one such campsite, a 14,000-year-old hunter’s rest stop outside the city of Tres Arroyos in Argentina, has given us a new understanding of how the pre-Clovis people might have lived.

Archaeologists are still uncertain how the pre-Clovis people arrived in the Americas. They came after the end of the ice age but at a time when glaciers and an icy, barren environment would still have blocked easy entrance into the Americas via Northern Canada. So it’s extremely unlikely that they marched over a land bridge from Siberia and into the Americas through the middle of the continent—instead, they would have come from Asia via a coastal route, frequently using boats for transport. That would explain why many pre-Clovis sites are on the coast, on islands, or on rivers that meet the ocean.
These early settlers were hunter-gatherers who used stone tools for a wide range of activities, including hunting, butchery, scraping hides, preparing food, and making other tools out of bone and wood. Many of the pre-Clovis stone tools look fairly simple and were made by using one stone to flake pieces off the other, thus creating sharp edges. At the campsite in Argentina, known as the Arroyo Seco 2 site, archaeologists have found more than 50 such tools made from materials like chert and quartzite. They’re scattered across an area that was once a grassy knoll above a deep lake, which is rich with thousands of animal bone fragments that have been carbon dated to as early as 14,000 years ago. There are even a couple-dozen human burials at the site, dated to a later period starting roughly 9,000 years ago. The spot has the characteristic look of a hunter’s camp, used for processing animals, that was revisited seasonally for thousands of years.

Writing in PLoS One, the researchers describe a number of reasons why a bunch of sharp-edged rocks and broken animal bones point to a 14,000-year-old human occupation of Argentina. First of all, there are far too many animal bones from a diversity of species grouped in one place for it to be accidental. Yes, there are some natural traps where we find massive numbers of prehistoric bones, but those are almost always in holes or depressions in the ground—and this area was on a rather high hill during the Pleistocene. Second, the stones aren’t just sharp-edged in a way that suggests flaking; many also show signs of wear and tear from scraping hide. “A large majority of the flaked edges were used transversely on dry skin,” the researchers write. “Consequently, it is likely that the skins were brought to the site in a state of intermediate processing.” Also, most of the stone used for the tools, including quartzite and chert, can only be found over 110km from Arroyo Seco. So that piece of evidence also points to human hunter-gatherers carrying tools with them over great distances.
The Pleistocene diet

One question remains. How can we be sure the tools at the site really are 14,000 years old? Archaeologists infer some of this from carbon dates on the animal bones, which have been tested by several labs around the world. The problem is that the site’s stratigraphy, or historical layers, are difficult to read due to erosion at the site. So even if a tool appears right next to a bone in a given layer, it may have come from later and been moved around by wind and water. That said, there is evidence that some of the early bones were broken by stone tools. A 14,000-year-old bone from Equus neogeus, an extinct American horse, bears distinct marks from a hammerstone. “This bone was intentionally broken while still fresh,” note the researchers.

With a firm connection between the human tools and the animal bones found at Arroyo Seco, we can begin to piece together what everyday life was like for these people—at least at mealtime. Analysis of more than 600 bone fragments out of thousands found at the site revealed that a large amount of these people’s meat came from animals that no longer exist. Various extinct horse species were a major part of the pre-Clovis diet, as were other extinct mammals like giant ground sloths, camels, mammoths, and giant armadillos. When these people arrived in South America, they found a land that no human had ever colonized. Many of these species would have been easy pickings for well-organized bands of hunters with sophisticated languages, tools, and tactics. Some paleoecologists hypothesize that these animals went extinct partly due to human hunting, and this campsite definitely provides evidence that extinct animals were part of the pre-Clovis diet for millennia. That said, Arroyo Seco contains far more bones from guanaco (a local relative of the camel) and rodents than it does from extinct mammals.

The absence of certain bones can tell us about how these people lived, too. Though there are bones from megafauna like the giant sloth Megatherium, we see no skulls, chest, or pelvic bones from the animal. The researchers speculate that’s because hunters would have done an initial butchery at the site where they killed or scavenged the animal and then transported parts of it to be processed at camp:

Given the body mass of this species (between 4 and 5 tons), it would have been extremely difficult to transport the entire carcass and even challenging to transport complete hindquarters weighing between 600 and 750 kg, and forequarters weighing between 250 and 300 kg. Taking into consideration these values, the best hypothesis is that the Megatherium was hunted or scavenged near the site, the skeleton was butchered into smaller parts, and these units were then transported to their current location at the site. The larger bones were transported with portions of meat already removed, and the bone may have been used for other purposes such as bone quarrying.

Of the extinct mammals that humans processed at Arroyo Seco, the most common seems to be horse. When people arrived in the Americas, it was full of at least two species of extinct horses. But by the time of the Inca and other great civilizations of South America, those animals were long gone. It wasn’t until Europeans arrived with their steeds that the continent was once again populated with horses.

Still, we can look back and imagine what it must have been like for those pre-Clovis people, entering a world where no human had ever gone before, full of animals that are legendary to us today. In many ways, they lived on a different planet than the one we inhabit now. At the edge of a now mostly vanished lake, on a knoll, those people fed their families, made tools, and strategized about how to hunt for game bigger than anything on land in the modern world. They returned year after year for centuries. Eventually, they buried their dead there among the animal bones left by their ancestors.

 

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