Tag Archives: south america

Native Americans made contact with Polynesians before European arrival

Indigenous Americans and Polynesians made epic voyages through the open ocean, encountering each other as early as 1200 A.D. That’s centuries before the arrival of Europeans, according to a new study, which looked at the genomes of modern inhabitants from Polynesia and the Americas.

Easter Island. Credit Flickr

The possibility of contacts between the two regions has been an area of interest for researchers for decades. Archeologists believed the two regions made early contact, mainly due to the early cultivation of a South American sweet potato in Polynesia. The results of this new genomic study now confirmed they did.

Alexander Ioannidis from Stanford University in California and his international colleagues analyzed genetic data from more than 800 individuals hailing from 15 indigenous American communities and 17 Polynesian islands. The “conclusive evidence” suggests early encounters between the two groups.

The study specifically looked for signs of early Polynesians and Indigenous Americans interbreeding, which would leave a clear genetic signature in their offspring. What they found was that people from Polynesian islands have genetic traces in their DNA linked to indigenous South Americans, especially with the Zenu tribe from Colombia.

Then, the researchers went on to trace the timing of the encounter, looking at the length of the indigenous American genomic segments. They finally estimated that the initial admixture took place in the eastern islands of Polynesia around 1150-1230 A.D. On Eastern Island, the encounter was much later at around 1380 AD, despite being the closest to South America.

“Our analyses suggest strongly that a single contact event occurred in eastern Polynesia, before the settlement of Rapa Nui, between Polynesian individuals and a Native American group most closely related to the indigenous inhabitants of present-day Colombia,” the study said.

Some open questions

While the study confirmed the encounter, it couldn’t clarify how it unfolded. South Americans may have drifted thousands of miles to the Pacific or Polynesians might have traveled to South America and mixed with the locals there. The question is still open for the researchers, who hope to continue looking into this.

The Polynesians are well known for their skills in ocean exploration because of their long voyages across the Pacific Ocean. They have traveled as far as the Hawaiian Island and Easter Island in the east and New Zealand in the south, looking for new settlements on canoes guided by the stars.

But some have argued that indigenous Americans also adventured to Polynesia, taking advantage of favorable weather conditions and currents. Back in 1947, Norwegian explorer Thor Heyerdahl famously sailed on a simple wooden raft from the coast of Peru to Polynesia, in order to prove his theory that people from South America could have colonized Polynesia.

The study adds more evidence to the early contact between indigenous Americans and Polynesians. Previously, researchers discovered hints of their connections in the sweet potato plant, which is from South America but was grown all over Polynesia before Europeans arrived in the Pacific.

In 2013, a study suggested that the sweet potato was first introduced to Polynesia between 1000 and 1100 A.D., most likely by Polynesian voyagers who reached the western coast of South America and brought back the crop, before spreading it to other Pacific islands.

The study was published in the journal Nature.

Tree rings reveal extreme weather is on the rise in South America

Since the mid-20th century, South America has seen unprecedented widespread and intense droughts as well as unusually wet periods, according to a new study. The authors claim that the increased volatility could be explained by climate change and atmospheric pollution.

Credit Flickr

Researchers have recently published the South American Drought Atlas, reconstructing over 600 years of changes in soil moisture in southern and central South America. The atlas is the result of field collection of three-ring records in Argentina, Chile, Uruguay, Paraguay, Bolivia, Peru and southern Brazil.

Ring widths usually reflect yearly changes in soil moisture. The date from the rings matched with historical droughts and floods from the Spanish colonial period, as well as with modern instrumental measurements. That’s why they were confident to extend their study back before written records.

The atlas showed there was a steady increase in the frequency of widespread droughts in South America since 1930, with the highest return times happening since the 1960s. Water shortages have severely affected Chile and Argentine especially from 1968-1969, 1976-1977, and 1996-1997.

“Increasingly extreme hydroclimate events are consistent with the effects of human activities, but the atlas alone does not provide evidence of how much of the observed changes are due to natural climate variability versus human-induced warming,” said lead author Mariano Morales in a statement. The new long-term record “highlights the acute vulnerability of South America to extreme climate events,” he said.

The South American atlas follows others that covered the climate conditions in North America; Asia; Europe and the Mediterranean; and New Zealand and eastern Australia. Studies building on the atlases have provided insights into the effects of droughts in past civilizations and the role of human-induced warming on the modern climate.

Factors behind weather changes

The researchers argued that periodic natural shifts in precipitation are driven by complex, interlocking patterns of atmospheric circulation in both land and sea. One of those factors is the low-level westerly winds that bring moisture to the continent from the Pacific, controlled by periodic cyclic changes in sea-surface temperature.

Shifts in these patterns, driven by increases in greenhouse gases, appear linked to a still continuing 10-year drought over central Chile and western Argentina, the study showed, which has caused severe water shortages, along with heavier than normal rains in eastern regions.

Another key factor mentioned by the researchers is the influence of the Southern Annular Mode, a belt of westerly winds, in precipitation. The belt periodically contracts southward or expands northward, and when it contracts, it weakens the westerly winds that bring rain to South America.

In recent decades, the winds have mainly focused on the south, a result of ozone-depleting chemicals used in 20th-century refrigerants that destroyed atmospheric ozone over Antarctica, scientists believe. The chemicals were banned in the 1980s, but their effects have persisted.

Finally, the last factor found is the so-called Hadley cell, a global phenomenon that lofts warm, moist air from near the equator and sends it further north and south, dropping precipitation as it goes. The air settles near the surface at predictable latitudes, by which time the moisture has been largely wrung out.

This creates permanently dry zones of the subtropics, including those in South America. The Hadley cell expanded towards the poles during recent decades, probably as a consequence of human-induced climate change. This caused changes in rainfall patterns and expanded the subtropical dry zones, especially in the Southern Hemisphere.

Coauthor Edward Cook, co-author, said in a statement, “We don’t want to jump off the cliff and say this is all climate change. There is a lot of natural variability that could mimic human-induced climate change.” However, he said, armed with the new 600-year record, scientists are better equipped to sort things out.

Currently, the drylands of central Chile and western Argentina are dealing with one of the most severe decade-long droughts on record. Crops of cereals and vegetables have been severely affected, with up to two-thirds of them being lost in some years. This threatens “the potential collapse of food systems,” said Morales.

At the same time, heavier than normal rain has been observed in southeastern parts of South America. Studies by Walter Baethgen, a researcher at Columbia University, showed more frequent extremely wet summers in the La Plata basin of Uruguay since 1970. This led to increases in crop and livestock production.

The study was published in the journal PNAS.

Largest turtle that ever lived had a shell with horns

Artist impression of a male Stupendemys geographicus with horns on its carapace and a female individual (left) swimming in freshwater. Credit: Artwork: Jaime Chirinos

South America’s tropical region is home to one of the world’s most biodiverse hotspots. But, this isn’t anything new. For millions of years, the South American rainforest has fostered unique fauna, including some of the most amazing extinct giant rodents and crocodilians, including crocodiles, alligators, caimans, and gavials. In a new study, researchers have enriched the continents’ mega-fauna, after they described an extinct freshwater turtle that may quite possibly be the largest to ever have lived.

It lived 13 million to 7 million years ago alongside frightening giant crocodilians

The extinct freshwater turtle called Stupendemys geographicus inhabited an area that today is a desert in Venezuela. Five to ten million years ago, however, this was a humid swampy region that was teeming with all kinds of life.

Paleontologists excavating one of the specimens of Stupendemys geographicus at the top of a cliff in northern Venezuela. Credit: Produced by Rio Verde for Edwin Cadena.

Stupendemys was first discovered in the mid-1970s, but an international team of researchers from Colombia, Venezuela, Brazil, and Switzerland, has now reported exceptionally well-preserved specimens of the extinct turtle — in the process — and we now know that this turtle was much more interesting than initially thought.

Venezuelan Palaeontologist Rodolfo Sánchez and a male carapace of the giant turtle Stupendemys geographicus, from Urumaco, Venezuela. Credit: Edwin Cadena.

For one, Stupendemys was huge. Its carapace was almost three meters long, making it one of the largest, if not the largest turtle that ever existed. Scientists estimate that the turtle could weigh as much as 1,145 kg — that’s almost 100 times more than its closest living relative, the big-headed Amazon river turtle (Peltocephalus dumerilianus).

Interestingly, some individuals exhibited an unexpected feature: horns on the carapace. Upon closer inspection, the researchers determined that the horns on the shell only appeared in males. This is the first time that sexual dimorphism in the form of horned shells has been reported in any side-necked turtle (any species of turtle belonging to the families Chelidae, Pelomedusidae, and Podocnemididae).

“The two shell types indicate that two sexes of Stupendemys existed—males with horned shells, and females with hornless shells,” says Marcelo Sánchez, director of the Paleontological Institute and Museum of the University of Zurich.

Despite its enormous size, Stupendemys wasn’t safe in the Venezuelan swamps. The giant turtle shared its habitat with Purussaurus brasiliensis, the largest caiman that ever lived, which grew to 12.5 meters in length, weighed around 8.4 metric tons, and required a mean daily food intake of 40.6 kg. Bite marks and punctured bones in fossil carapaces of Stupendemys support the notion that the turtle was subjected to predation.

Newly described jaws and partial skeletons belonging to Stupendemys also proved essential at revising its position in the evolutionary family tree, suggesting that some living turtles from the Amazon are its closest living relatives. The study published in the journal Science Advances also determined that the giant extinct turtle’s range extended across the entire northern part of South America, based on fossils retrieved from Brazil, Columbia, and Venezuela.

8 bird species have disappeared this decade or are on the brink of extinction

Credit: Cinemablend.

Unlike the animation Rio, in real life, there are no more Spix’s Macaws left in the wild. Credit: Cinema Blend.

In the 2011 animation film Rio, a captive-raised Spix’s Macaw by the name of Blu arrives in Brazil to mate with the last-known wild member of his species, a female named Jewel. In real life, however, Rio would have arrived a decade too late.

According to a recent study, the last wild Spix’s Macaw disappeared in 2000 and the species is now presumed extinct apart from a handful of specimens born and raised in captivity. Along with it are seven other bird species that have suffered the same fate in the last decade.

The study, funded by the non-profit BirdLife International, statistically analyzed 51 critically endangered bird species and found that eight could likely be classified as extinct or very close to extinction. Specifically, three are already extinct, one is extinct in the wild — there are an estimated 70 Spix’s Macaws (Cyanopsitta spixii), left in the world, all captive — and four are extremely close to extinction, if not already gone.

The extinct bird species identified in the new study are the Brazilian cryptic tree hunter (Cichlocolaptes mazarbarnetti), last seen in 2007; the Brazilian alagoas foliage-gleaner (Philydor novaesi), last seen in 2011; and the Hawaiian black-faced honeycreeper (Melamprosops phaeosoma), last seen in 2004.

A total of 187 species of birds have gone extinct since scientists started keeping records. Historically, birds native to islands have been the most vulnerable due to invasive species, but deforestation ramped by expanding agriculture and logging is growing fast as the leading driver of avian extinction.

“Ninety percent of bird extinctions in recent centuries have been of species on islands,” said Dr. Stuart Butchart, BirdLife’s Chief Scientist and lead author on the paper. “However, our results confirm that there is a growing wave of extinctions sweeping across the continents, driven mainly by habitat loss and degradation from unsustainable agriculture and logging”.

Adult Spix's macaw in Vogelpark Walsrode, Germany in 1980. Credit: Wikimedia Commons.

Adult Spix’s macaw in Vogelpark Walsrode, Germany in 1980. Credit: Wikimedia Commons.

Butchart and colleagues hope that their work will inspire more action to prevent other extinctions. Five of the eight extinctions reported in the journal Biological Conservation involve species in South America, four of which happened in Brazil. The Amazon, where most of these extinct species were once abundant, lost 17 million hectares of forest between 2001 and 2012. Unlike other animals, birds are more vulnerable to habitat loss because they often occupy ecological niches, consuming specific prey and nesting in specific trees.

“Our results confirm that there is a growing wave of extinctions sweeping across the continents, driven mainly by habitat loss and degradation from unsustainable agriculture and logging,” said Butchart.

Abrupt climate change killed off ancient South American populations

Humans colonized South America with impressive ease and speed, but some 8,000 years ago, a sharp decline started taking place. Now, researchers have shown that climate change was responsible for this decline.

Image in public domain.

The initial human colonization of South America was a rapid process. Hunter-gatherers arrived on the continent some 14,000 years ago, and within a few millennia, they covered every biome on the continent. However, while colonists were largely successful in their attempts, there was a period of about 4,000 years when things didn’t go so well. Researchers have found that a period called the Middle Holocene (8200 to 4200 cal BP) featured numerous shifts in climatic events.

“Archaeologists working in South America have broadly known that some 8,200 years ago, inhabited sites in various places across the continent were suddenly abandoned. In our study we wanted to connect the dots between disparate records that span the Northern Andes, through the Amazon, to the southern tip of Patagonia and all areas in between,” said Dr. Philip Riris (UCL Institute of Archaeology), lead author of the new study.

Through the analysis of radiocarbon dates using computer algorithms, they found that long-term rain patterns greatly correlate with the archaeological evidence. In other words, when the climate started to change, populations started to decline.

“Unpredictable levels of rainfall, particularly in the tropics, appear to have had a negative impact on pre-Columbian populations until 6,000 years ago, after which recovery is evident. This recovery appears to correlate with cultural practices surrounding tropical plant management and early crop cultivation, possibly acting as buffers when wild resources were less predictable,” added Dr. Riris.

However, it wasn’t the absolute magnitude of climate change that did most of the damage, but rather the frequency of exceptional climatic events. This is particularly interesting for us since while the overall trend of climate change is, in rough terms, rather clear, extreme weather events caused by climate change are much harder to foresee.

In other words, it wasn’t necessarily that there was more or less rainfall, but rather that the changes from low to high occurred much quicker than they were supposed to. Dr. Riris explained:

“We studied ancient records of rainfall such as marine sediments for evidence of exceptional climate events. Within windows of 100 years, we compared the Middle Holocene to the prevalent patterns before and after 8,200 years ago. Normal patterns of rainfall suggest on average an unusually dry or wet year every 16-20 years, while under highly variable conditions this increases to every 5 years or so.”

[panel style=”panel-info” title=”Climate change” footer=””]If you’re a climate change denier, I know what you’re thinking: Aha! So climate has changed before in the past. Absolutely, our planet’s climate has changed and is changing all the time. However, there is overwhelming evidence that the current warming trends, along with all the events and consequences that derive from it, are caused by mankind’s emission of greenhouse gases, especially carbon dioxide.[/panel]

The study was published in Scientific Reports.

Zika virus solution might lie in oil of common flower

As the Zika virus outbreak threatens to spread from South America to the rest of the world, scientists are scrambling to find a cure for the mosquito-borne disease. Although Brazil is currently using synthetic pesticides and transgenic mosquitos in an attempt to control the Aedes aegypti mosquitos that carry the virus, a team of New York University (NYU) scientists is now suggesting that the answer might be as simple as a common flower and a pot of boiling water.

The Mexican Marigold flower that could be the key to fighting the Zika virus. Credit: New York University

The Mexican Marigold flower that could be the key to fighting the Zika virus. Credit: New York University

Some plants have evolved chemical defenses in the form of potent insecticides to protect themselves from insect damage. For example, pyrethrins are commonly used as an insecticide and insect repellant and originate from a type of Chrysanthemum flower.

Back in 1991, a study published in the Journal of the American Mosquito Control Association found that the essential oil of the Tagetes minuta plant – also known as the Mexican Marigold – can kill A. aegypti larvae for at least nine days at just 40 parts per million, which is considered to be a very small amount.

Using this research as a foundation, NYU chemical and biomolecular engineering professor Mark Green and his team discovered that this essential oil is a potent larvicide when added to standing water, which is where the A. aegypti mosquitos lay their eggs. Green claims that since these particular mosquitos spread the Zika virus – along with the dengue, yellow fever and chikungunya viruses – at a local level, this kind of treatment is very effective.

“This mosquito bites where it’s born, so by treating standing water in an area, you can effectively eliminate that population,” he said, adding that these natural pesticides are much safer than synthetic alternatives. “You could make this yourself and use it around the yard, just by boiling the plant and treating any standing water.”

Although pesticide demand is increasing due to the recent fears of a Zika spread, Green suggests that scientists invest more effort into natures chemical defenses such as the oil of the Mexican Marigold.

“These plant chemicals are the product of hundreds of millions of years of evolution, as plants learned to defend themselves against similar insects,” he said. “Why shouldn’t we take advantage of that intelligence to protect ourselves?”

Cano Cristales – the world’s most colourful river

Caño Cristales is a river located in Northern Columbia, with a length of almost 100 km and a width of under 20 meters. If you look at it, you’d be tempted to think this is some sort of illusion or photographic trick, but you’d be wrong.

Photo by Mario Carvajal.

Photo by Mario Carvajal.

It’s quite remote, and you can get there only by foot, horses and donkeys, but that doesn’t stop tourists from flooding in. There were so many of them that visiting it was actually forbidden for several years. Now it’s open, but within reasonable limits. The river is a rainbow of colors, changing from corner to corner.

Photo by Mario Carvajal.

Photo by Mario Carvajal.

Photo by Mario Carvajal.

Photo by Mario Carvajal.

The hard rocks which make most of the bottom of the river are covered with moss, which most of the year have a dull green or brown colour. In the rainy season the water is too deep for the colours to bloom, and in the dry season there’s just not enough water to support all the moss.

Photo by Mario Carvajal.

Photo by Mario Carvajal.

Photo by Mario Carvajal.

Photo by Mario Carvajal.

However, there is a window during these seasons when the water level is just right, and the dazzling display of colours appears to delight the eye.

Uno de los lugares más hermosos de Caño Cristales es el sector conocido como Los Ochos, donde se encuentran formaciones rocosas de gran belleza, llamadas Marmitas de Gigante — Licencia Creative Commons Reconocimiento 4.0 Internacional. Algunos derechos reservados, 2014 por Fotur / Fotografía: Mario Carvajal (http://www.mariocarvajal.com). Usted puede usar esta foto gratuitamente según la licencia establecida en Fotur (http://www.fotur.org), haciendo el v'inculo hacia www.cano-cristales.com

Photo by Mario Carvajal.


Photo by Mario Carvajal.

Photo by Mario Carvajal.




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