Archaeologist uncovers hidden history of conquistadors in American South

Chris Rodning, the Paul and Debra Gibbons Professor in the Tulane School of Liberal Arts’ Department of Anthropology, unravels early entanglements between Native Americans and European explorers, revealing how their interactions shaped the history of the American South.

An image taken in June 2017 by a camera mounted on a drone displays the exposed remnants of Fort San Juan.
Excavations of this area of the site will be continued in June 2018 [Credit: Ryan Wallace]

“Native Americans’ responses to Spanish explorers and colonists form an important part of the story behind the history of European colonialism in North America,” said Rodning, who conducts archaeological research at Fort San Juan — the earliest known permanent European settlement in the interior United States, located near Morganton, North Carolina.

Since 2001, Rodning has collaborated with David Moore, an anthropology professor from Warren Wilson College, and Rob Beck, an associate professor of anthropology from the University of Michigan, to excavate the site.

“In 2013, we identified the archaeological footprint of the fort,” said Rodning, noting that the team has since focused on learning how the structure was built and where it was located in relation to a nearby Native American settlement called Joara.

In 1540, the conquistador Hernando de Soto traversed this part of western North Carolina.

“He threatened communities with violence, demanded food and sometimes attacked when they did not comply with his demands. He also pressed Native Americans into service as porters to carry supplies for his men,” said Rodning.

Hannah Hoover, a Tulane senior double majoring in anthropology and classical studies, digs dirt from excavation
squares at the Fort San Juan site and throws it up to sifters to screen the dirt in search of artifacts
[Credit: Christopher Rodning]

One generation after de Soto’s expedition, Spanish explorer Juan Pardo arrived with another group of soldiers and established Fort San Juan in 1566.

“When Pardo marched inland, the town of Joara was a much more powerful town than it had been 26 years previously,” said Rodning — possibly because of Joara’s previous interactions with de Soto.

At first, an alliance formed between Pardo and the people of Joara, but in 1568, warriors from Joara sacked the fort and burned the compound.

“Architectural materials and designs of burned houses at the site demonstrate evidence of the typical Native American style of architectural design and construction, but some wooden fragments also indicate that they were cut and shaped with metal tools. The significance of that is Native Americans didn’t have those types of metal tools,” said Rodning.

Rodning said that it’s likely that Native Americans gained access to these new tools from Spanish soldiers, or that Spanish soldiers participated in the construction and maintenance of houses where the men garrisoned at Fort San Juan lived.

Rodning said his team remains committed to the project in hopes of understanding how early moments and subsequent episodes of Spanish contact changed Native American communities in this region.

University Press of Florida published the group’s findings in a book called Fort San Juan and the Limits of Empire: Colonialism and Household Practice at the Berry Site in 2016.

Source: Tulane University [February 27, 2018]

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Fossil turtle species, 5.5 million years old, sheds light on invasive modern relatives

A University of Pennsylvania paleontologist has described a 5.5 million-year-old fossil species of turtle from eastern Tennessee. It represents a new species of the genus Trachemys, commonly known as sliders, which are frequently kept as pets today.

Trachemys haugrudi represents a new species of fossil turtle that lived in what is now eastern Tennessee
more than 5.5 million years ago [Credit: Mary P. Williams]

Steven Jasinski, author of the new study, is a doctoral student at the University of Pennsylvania and acting curator of paleontology and geology at the State Museum of Pennsylvania. He is completing his Ph.D. at Penn under Peter Dodson, a professor of paleontology in the Department of Earth and Environmental Science in the School of Arts and Sciences and a professor of anatomy in the School of Veterinary Medicine.

The study published in PeerJ Journal, investigated a fossil turtle found around the Miocene-Pliocene boundary in the Gray Fossil Site, an area rich with fossils in eastern Tennessee near East Tennessee State University, where Jasinski completed his master's degree. The site represents an ancient sinkhole surrounded by a forest from which dozens of fossil animal species have been characterized, including new species of red panda, Eurasian badger, kinosternid turtle, and colubrid snake.

Thorough examination of the dozens of turtle fossils from the site revealed important differences between this turtle and other known fossil and living species. Jasinski named the fossil turtle Trachemys haugrudi, after Shawn Haugrud, the lab and field manager and lead preparer at the Gray Fossil Site.

"Shawn has spent an incredible number of hours working on these specimens," Jasinski said. "He cleaned and prepared the fossils and was able to essentially glue this turtle back to life, giving me numerous nearly complete turtle shells to use in this research. Without all that time and effort, I wouldn't have been able to determine nearly as much about this turtle as I did.

"Shawn also didn't do this work alone, as numerous other people including volunteers worked on these fossils and got them prepared so that I could complete my research. They really did all the hard work, and I was then able to determine why it was new and what its implications are" he said.

Turtles are best known for their shells, and indeed it is this feature of their anatomy that is commonly found as fossils. Yet the fossil shells are typically found in broken pieces. Often gaps or holes remain, or only single small pieces are found, and the whole must be inferred from other information, including other fossil and living creatures.

Though initially found in pieces, Gray Fossil Site preparator Shawn Haugrud was able to glue the shell of this species
back together, enabling Penn's Steven Jasinski to complete an analysis of the turle. Jasinski named the species
 in Haugrud's honor [Credit: University of Pennsylvania]

"It is extremely rare to get more complete fossils," Jasinski said, "but Trachemys haugrudi, commonly called Haugrud's slider turtle, provides me with dozens of shells, and several are nearly complete."

Haugrud's slider turtle was a fairly small turtle, not more than approximately 10 inches (25 cm) in total shell length, smaller than the modern-day red-eared slider turtle, Trachemys scripta elegans. Red-eared slider turtles are commonly purchased as pets, though they can grow large, and some owners release them into the wild. As a result, though native to the southeastern United States, red-eared sliders have become one of the most invasive animal species in the world today, found on every continent except Antarctica.

"People tend to see all turtles as similar and release them into whatever pond or river is close by when they no longer want to care for them," Jasinski said. "Once released, however, they often outcompete native species. It is a problem that scientists are still dealing with."

As part of the study, Jasinski sought to determine where Trachemys haugrudi was positioned in the evolution of similar turtles both within the genus and in related genera. He performed a phylogenetic analysis, a method that compares shapes and features of different species to determine how similar or dissimilar and therefore how closely related they may be. He found Haugrud's to be most closely related to a group of fossil Trachemys turtles from Florida and next most closely related to a distinct group of fossil Trachemys from the midwestern U.S. Together, these fossil Trachemys form a closely related group situated within other still-living species of Trachemys.

Today, distinct, closely-related groups of Trachemys species dwell in Mexico, Central and South America, and the Caribbean. Jasinski's investigation, along with other information from previous studies, indicates that one group evolved in Mexico and Central and South America and evolved into different species within this geographic area, and another group evolved separately in the Caribbean.

Species from the U.S., including the red-eared slider turtle, are found near the base of their "branch" of the Trachemys family tree; their fossil ancestors are still waiting to be discovered. The fossil Trachemys species in Jasinski's analysis are on a distinct part of the Trachemys tree, and current understanding suggests that they did not give rise to the modern species living today.

Trachemys haugrudi is the latest in a rich array of fossils, including species of red panda, badger, and snake, that have
been identified from the Gray Fossil Site, located in eastern Tennesse [Credit: University of Pennsylvania]

The findings imply that there was once much greater diversity in Trachemys turtles than exists today. It seems that many of the ancient slider species died out without leaving any direct descendents, perhaps because they lacked the ability to adapt to different environments.

"While Trachemys turtle species are considered plastic, implying they can adapt to and live in many environments, this adaptive lifestyle may be a relatively newer characteristic of these turtles," Jasinski said. "More fossils are needed to better understand if this aspect of their evolution is a recent addition."

To get a handle on invasive turtles, understanding more about their ancient relatives could only be helpful, Jasinski said.

"Trachemys haugrudi helps provide more information on Trachemys and begins to offer us insights into the evolution of an animal that has become a problematic invader in many areas of the world," he said. "Understanding how something evolved into its present form may help us understand why an animal is so adaptive and good at invading new areas and outcompeting native species. If we can see that Trachemys today are especially adaptive because evolution has allowed them to become more generalized through time, we can use that information to determine where they may invade, what species they may outcompete and what we can do to counteract those invasions or help native species compete against them."

Jasinski is undertaking further study into the fossil species of not only Trachemys but other turtles within the family Emydidae, which includes Trachemys. He hopes that further data and fossils will help shed light on other turtle species and provide a clearer understanding of the evolution of this group of mainly New World turtles.

Author: Katherine Unger Baillie | Source: University of Pennsylvania [February 26, 2018]

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Extinct lakes of the American desert west

The vestiges of lakes long extinct dot the landscape of the American desert west. These fossilized landforms provide clues of how dynamic climate has been over the past few million years.

Erosional Pleistocene shorelines in Surprise Valley, California, USA [Credit: Anne Egger]

Identification of ancient lake shoreline features began with early explorers of the continent. The first detailed studies were conducted by pioneering American geologists such as G.K. Gilbert and I.C. Russell in the late 1800s, who studied Lake Bonneville, now the remnant Great Salt Lake in Utah, and Lake Lahonton, located in northwestern Nevada.

Through this long history of studying fossil shorelines and lake sediments, we know that these lakes existed during two periods with distinct environmental conditions during the geologically recent past. The first was during ice age maxima, such as the last ice age, 14 to 30 thousand years ago, when global temperatures were 4 to 6 degrees colder and continental ice sheets expanded into the continental United States.

The second time period was about three million years ago during the middle of the Pliocene epoch--a global climate characterized by warmer temperatures and atmospheric CO2 levels roughly equivalent to today's values, which has led many scientists to view the Pliocene as a potential analogue for future climate change.

These observations lead to an important question, says the study's lead author, Daniel Ibarra, "Why are there lake systems under both colder and warmer climates, but not today?" Of particular interest, he says, is the presence of lakes under warmer conditions, which, under a "wet gets wetter, dry gets drier" paradigm, goes against projections of future warming.

Shorelines of Lake Bonneville along the Oquirrh Mountains, Utah, USA. (H.H. Nichols [artist] and G.K. Gilbert,
in Gilbert, 1884) [Credit: H.H. Nichols [artist] and G.K. Gilbert, in Gilbert, 1884. Public domain]

To answer this question, Ibarra and colleagues looked at the competing influences of temperature and precipitation, and how they combine to allow for the existence of lakes under these dual climate states.

The authors compiled evidence for, and created models of, lakes during both colder and warmer than modern periods of the Pliocene-Pleistocene (the last 5 million years). During colder glacial periods, they found that increased precipitation and decreased evaporation combined to form large lakes that occupied the inward draining basins in the western United States, particularly in northern Nevada and Utah.

Increased precipitation also drove the formation of lakes, particularly in southern Nevada and southern California during the warmer middle Pliocene, outpacing higher temperatures and evaporation rates during that time. This increase in precipitation during the middle Pliocene and dominantly southwestern distribution of lake deposits is similar to the pattern of precipitation during modern El Niño years, corroborating previous hypotheses for mean "El Niño-like" conditions during the mid-Pliocene.

The team's interdisciplinary approach explains the conditions driving lake systems in mid-latitude regions today and over the geologic past. Further, notes Ibarra, "This work illustrates the importance of understanding how the El Niño Southern Oscillation drives precipitation patterns in arid regions, which is important for future water resources planning for the western United States."

The study appears in the Geological Society of America Bulletin.

Source: Geological Society of America [February 22, 2018]

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Scientists create 'Evolutionwatch' for plants

Using a hitchhiking weed, scientists from the Max Planck Institute for Developmental Biology reveal for the first time the mutation rate of a plant growing in the wild.

Scientists created an 'Evolutionwatch' for plants [Credit: Moises Exposito-Alonso,
Claude Becker and colleagues]

They compared 100 historic and modern genomes of the tiny plant Arabidopsis to measure precisely the rate at which it evolves in nature. The oldest plant, preserved in a herbarium, was from 1863. At this time, the scientists estimate the species had already more than 200 years in the New World behind it. Two different methods gave the same result, that Arabidopsis had been introduced by Europeans who arrived on the US East Coast around the year 1600. It was almost certainly introduced there by chance, perhaps carried on the boots of Europeans, or mixed in with the seeds of edible plants.

The team focused on samples from North America, because they knew that one particular genetic family of Arabidopsis was very widespread, presenting an opportunity to observe newly-acquired mutations. The comparison of 100 complete genomes revealed 5000 new mutations, some of which could have given the plant an adaptive advantage as it colonised its new environment. The plant moved inland alongside human settlers, gradually diverging from the European ancestor from which it originated. Samples of the species along the same path today reveal increasingly deep and fast-growing roots, perhaps evidence that it adapted during its hitchhiking trip.

"Collections of invasive populations sampled from different times in history enable us to observe the 'live' process of evolution in action," says Moises Exposito-Alonso, first author of the paper published in PLOS Genetics.

They sequenced the genomes of 100 plants collected by botanists between 1863 and 2006. All samples from before 1990 came from museum collections of dried plants. The oldest dried plants, preserved in time 150 years ago, show how much they had evolved by that time. The youngest plants continued to change and evolve. By comparing genomes of plants that had diverged from a common ancestor for different amounts of times, the scientists calculated how many mutations the plant acquires a year.

This in turn enabled the team to deduce that the last common ancestor of the lineage must have lived at the end of the 16th or beginning of the 17th century, coinciding with the time that many people were arriving by boat from Europe, particularly the southern UK, west coast of France and the Netherlands. This was very surprising, since a previous estimate, which had not made use of genetic information from dried herbarium samples, suggested that the colonizing Arabidopsis plants had only arrived in the 19th century.

Arabidopsis is not a harmful weed, but the findings help reveal some of the fundamental evolutionary processes behind the ability of invasive species to colonise new environments. In particular, they unlock some of the secrets of the "genetic paradox of invasion". This occurs when a colonizer with low genetic diversity is nevertheless surprisingly successful in a new environment.

To determine the effect of new mutations, the scientists grew some of the plants in the lab to identify any differences in growth. The fact that such differences were found suggests that some of the mutations that appeared during the past 400 years conferred an advantage during colonisation.

"We were very surprised, since scientific dogma suggests that evolution normally proceeds at a much slower pace," said Hernan Burbano, one of the supervisors of this study.

"Accurate evolutionary rates for plants and animals will be fundamental to reconstruct their past history and to predict the opportunity of novel advantageous traits to arise. Our results show that herbarium and animal specimens can be the source of a great new branch of genetics in future," Exposito says.

Source: Public Library of Science [February 21, 2018]

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