COVID-19 is only the latest infectious disease to have had an outsized impact on human life. A new study employing ancient human DNA reveals how tuberculosis has affected European populations over the past 2,000 years, specifically the impact that disease has had on the human genome. This work, which publishes March 4 in theAmerican Journal of Human Genetics, has implications for studying not only evolutionary genetics, but also how genetics can influence the immune system.
"Present-day humans are the descendants of those who have survived many things--climate changes and big epidemics, including the Black Death, Spanish flu, and tuberculosis," says senior author Lluis Quintana-Murci of the Institut Pasteur in France. "This work uses population genetics to dissect how natural selection has acted on our genomes."
This research focused on a variant of the gene TYK2, called P1104A, which first author Gaspard Kerner had previously found to be associated with an increased risk of becoming ill after infection with Mycobacterium tuberculosis when the variant is homozygous. (TYK2 has been implicated in immune function through its effect on interferon signaling pathways.) Kerner, a PhD student studying genetic diseases at the Imagine Institute of Paris University, began collaborating with Quintana-Murci, an expert in evolutionary genomics, to study the genetic determinants of human tuberculosis in the context of evolution and natural selection.
Using a large dataset of more than 1,000 European ancient human genomes, the investigators found that the P1104A variant first emerged more than 30,000 years ago. Further analysis revealed that the frequency of the variant drastically decreased about 2,000 years ago, around the time that present-day forms of infectious Mycobacterium tuberculosis strains became prevalent. The variant is not associated with other infectious bacteria or viruses.
"If you carry two copies of this variant in your genome and you encounter Mycobacterium tuberculosis, you are very likely to become sick," Kerner says. "During the Bronze Age, this variant was much more frequent, but we saw that it started to be negatively selected at a time that correlated with the start of the tuberculosis epidemic in Europe."
"The beauty of this work is that we're using a population genetics approach to reconstruct the history of an epidemic," Quintana-Murci explains. "We can use these methods to try to understand which immune gene variants have increased the most over the last 10,000 years, indicating that they are the most beneficial, and which have decreased the most, due to negative selection."
He adds that this type of research can be complementary to other types of immunology studies, such as those performed in the laboratory. Moreover, both researchers say these tools can be used to study the history and implications of many different genetic variants for multiple infectious diseases.
IMAGE: REPLICA OF A WOOLLY MAMMOTH (MAMMUTHUS PRIMIGENIUS) IN THE ROYAL BC MUSEUM IN VICTORIA, BRITISH COLUMBIA, CANADA. THE DISPLAY IS FROM 1979, AND THE FUR IS MUSKOX HAIR. view more
Woolly mammoths may have walked the landscape at the same time as the earliest humans in what is now New England, according to a Dartmouth study published in Boreas. Through the radiocarbon dating of a rib fragment from the Mount Holly mammoth from Mount Holly, Vt., the researchers learned that this mammoth existed approximately 12,800 years ago. This date may overlap with the arrival of the first humans in the Northeast, who are thought to have arrived around the same time.
"It has long been thought that megafauna and humans in New England did not overlap in time and space and that it was probably ultimately environmental change that led to the extinction of these animals in the region but our research provides some of the first evidence that they may have actually co-existed," explains co-author Nathaniel R. Kitchel, the Robert A. 1925 and Catherine L. McKennan Postdoctoral Fellow in anthropology at Dartmouth.
The Mount Holly mammoth, Vermont's state terrestrial fossil, was discovered in the summer of 1848 in the Green Mountains during the construction of the Burlington and Rutland railroad lines. One molar, two tusks, and an unknown number of bones were excavated from a hilltop bog near Mount Holly. Over time, the specimens became scattered across several repositories, as they transferred from one collection to the next. A rib fragment from the Mount Holly mammoth became part of the Hood Museum of Art's collection and some of the other skeletal materials are now housed at the Museum of Comparative Zoology at Harvard University and the Mount Holly Historical Museum.
Kitchel stumbled across the Mount Holly mammoth rib fragment last December at the Hood Museum's offsite storage facility, as curators had invited him to take a look at some of their artifacts from New Hampshire and Vermont. He came across a large bone (approximately 30 cm. in length) that was stained brown in color from age. He had a hunch that this was the remains of a mammoth and when he looked down at the tag, it read, "Rib of fossil elephant. Mt. Holly R.R. cut. Presented by Wm. A. Bacon Esq. Ludlow VT." This was rather serendipitous for Kitchel, as he had recently delivered a talk at Mount Holly's Historical Museum for which he had read up on the Mount Holly mammoth.
To appreciate the significance of the Mount Holly mammoth remains, including the rib fragment, it is helpful to understand the paleontology of the Northeast. During the Last Glacial Maximum around 18,000 - 19,000 years ago when glaciers were at their maximum extent, the ice began to retreat, gradually exposing what is now New England. During that period, it is likely that the glaciers probably sufficiently ripped up whatever soil might have been preserving fossils, reducing the likelihood for fossils to remain intact. These changes combined with the Northeast's naturally acidic soils have created inhospitable conditions for the preservation of fossils. While Kitchel had discussed the complicated paleontology of the Northeast in the past with colleague and co-author Jeremy DeSilva, an associate professor of anthropology at Dartmouth, he never thought that he would have much of an opportunity to work on it.
After seeing this mammoth material in the Hood's collection, he and DeSilva decided to obtain a radiocarbon date of the fragmentary rib bone. They took a 3D scan of the material prior to taking a small (1 gram) sample from the broken end of the rib bone. The sample was then sent out to the Center for Applied Isotope Studies at the University of Georgia for radiocarbon dating and a stable istotopic analysis.
Radiocarbon dating enables researchers to determine how long an organism has been dead based on its concentration of carbon-14, a radioactive isotope that decays over time. Stable isotopes however, are isotopes that do not decay over time, which provide a snapshot of what was absorbed into the animal's body when it was alive. Nitrogen isotopes can be used to analyze the protein composition of an animal's diet. The nitrogen isotopes of the Mount Holly mammoth revealed low values in comparison to that of other recorded mammoths globally while also reflecting the lowest value recorded in the Northeast for a mammoth. The low nitrogen values could have been the result of these mega-herbivores having to consume alder or lichens (nitrogen fixing species) during the last glacial period when the landscape was denser due to climate warming.
"The Mount Holly mammoth was one of the last known occurring mammoths in the Northeast," says DeSilva. "While our findings show that there was a temporal overlap between mammoths and humans, this doesn't necessarily mean that people saw these animals or had anything to do with their death but it raises the possibility now that maybe they did."
The radiocarbon date for the Mount Holly mammoth of 12,800 years old overlaps with the accepted age of when humans may have initially settled in the region, which is thought to have occurred during the start of the Younger Dryas, a final pulse of glacial cold before temperatures warmed dramatically, marking the end of the Pleistocene (Ice Age).
While other research on mammoths in the Midwest suggests that humans hunted and buried these animals in lakes and bogs to preserve the meat, there's little evidence that early humans in New England hunted or scavenged these animals.
The researchers are intrigued by the Mount Holly mammoth. The rest of its rib and other bones could be waiting to be discovered. Or, through time, they could have broken apart, dissolved in the acidic soil, or a scavenger could have run off with the bones. There are still a lot of unknowns; yet, the team has already begun further research using modern and more sophisticated archaeological techniques to explore what may be underground at Mount Holly.
IMAGE: LITTLE FOOT FOSSIL SKULL IN DIAMOND'S BEAMLINE I12 view more
CREDIT: COPYRIGHT DIAMOND LIGHT SOURCE LTD
In June 2019, an international team brought the complete skull of the 3.67-million-year-old Little Foot Australopithecus skeleton, from South Africa to the UK and achieved unprecedented imaging resolution of its bony structures and dentition in an X-ray synchrotron-based investigation at the UK's national synchrotron, Diamond Light Source. The X-ray work is highlighted in a new paper in e-Life, published today (2nd March 2021) focusing on the inner craniodental features of Little Foot. The remarkable completeness and great age of the Little Foot skeleton makes it a crucially important specimen in human origins research and a prime candidate for exploring human evolution through high-resolution virtual analysis.
To recover the smallest possible details from a fairly large and very fragile fossil, the team decided to image the skull using synchrotron X-ray micro computed tomography at the I12 beamline at Diamond, revealing new information about human evolution and origins. This paper outlines preliminary results of the X-ray synchrotron-based investigation of the dentition and bones of the skull (i.e., cranial vault and mandible).
Leading author and Principal Investigator, Dr Amelie Beaudet, Department of Archaeology, University of Cambridge and honorary research at the University of the Witwatersrand (Wits University) explains: "We had the unique opportunity to look at the finest details of the craniodental anatomy of the Little Foot skull. While scanning it, we did not know how well the smallest structures would be preserved in this individual, who lived more than 3.5 million years ago. So, when we were finally able to examine the images, we were all very excited and moved to see such intimate details of the life of Little Foot for the first time. The microstructures observed in the enamel indicate that Little Foot suffered through two clear periods of dietary stress or illness when she was a child."
The team were also able to observe and describe the vascular canals that are enclosed in the compact bone of the mandible. These structures have the potential to reveal a lot about the biomechanics of eating in this individual and its species, but also more broadly about how bone was remodelled in Little Foot The branching pattern of these canals indicates some remodelling took place, perhaps in response to changes in diet, and that Little Foot died as an older individual.
The team also observed tiny (i.e., less than 1 mm) channels in the braincase that are possibly involved in brain thermoregulation (i.e., how to cool down the brain). Brain size increased dramatically throughout human evolution (about threefold), and, because the brain is very sensitive to temperature change, understanding how temperature regulation evolves is of prime interest. Dr Amelie Beaudet adds: "Traditionally, none of these observations would have been possible without cutting the fossil into very thin slices, but with the application of synchrotron technology there is an exciting new field of virtual histology being developed to explore the fossils of our distant ancestors."
Dr Thomas Connolley, Principal Beamline Scientist at Diamond commented: "Important aspects of early hominin biology remain debated, or simply unknown. In that context, synchrotron X-ray imaging techniques like microtomography have the potential to non-destructively reveal crucial details on the development, physiology, biomechanics and taxonomy of fossil specimens. Little Foot's skull was also scanned using the adjacent IMAT neutron instrument at ISIS Neutron and Muon Source, combining X-ray and neutron imaging techniques in one visit to the UK. With such a rich volume of information collected, we're eager to make more discoveries in the complementary X-ray and neutron tomography scans."
Applications of X-ray synchrotron-based analytical techniques in evolutionary studies have opened up new avenues in the field of (paleo)anthropology. In particular, X-ray synchrotron microtomography has proved to be enormously useful for observing the smallest anatomical structures in fossils that are traditionally only seen by slicing through the bones and looking at them under a microscope. Through the last decade, there have been more studies in palaeoanthropology using synchrotron radiation to investigate teeth and brain imprints in fossil hominins. However, scanning a complete skull such as the one of Little Foot and aiming to reveal very small details using a very high-resolution was quite challenging, but the team managed to develop a new protocol that made this possible. To recover the smallest possible details from a fairly large and very fragile fossil, the team decided to image the skull using synchrotron X-ray micro computed tomography at the I12 beamline at Diamond.
Principal Investigator, and Associate Professor, Prof Dominic Stratford, University of Witwatersrand (Wits University), School of Geography, Archaeology and Environmental Studies says: "This level of resolution is providing us with remarkably clear evidence of this individual's life. We think there will also be a hugely significant evolutionary aspect, as studying this fossil in this much detail will help us understand which species she evolved from and how she differs from others found at a similar time in Africa. This is just our first paper so watch this space. Funding permitting, we hope to be able to bring other parts of Little Foot to Diamond," adding:
"This research was about bringing the best-preserved Australopithecus skull to the best of the best synchrotron facility for our purposes. Traditionally, hominins have been analysed by measuring and describing by the exterior shapes of their fossilised bones to assess how these differ between species. Synchrotron development and microCT resources means that we are now able to virtually observe structures inside the fossils, which hold a wealth of information. More recently, technology has developed to such an extent that we can now virtually explore minute histological structures in three dimensions, opening new avenues for our research."
The first bones of the Little Foot fossil were discovered in the Sterkfontein Caves, northwest of Johannesburg, by Professor Ron Clarke of the University of the Witwatersrand in 1994. In 1997, following their discovery of the location of the skeleton, Professor Clarke and his team spent more than 20 years painstakingly removing the skeleton in stages from the concrete-like cave breccia using a small airscribe (a vibrating needle). Following cleaning and reconstructing, the skeleton was publicly unveiled in 2018. Wits University is the custodian of the StW 573, Little Foot, fossil.
Professor Ron Clarke, the British scientist based in South Africa who discovered and excavated Little Foot and conducted all the early examinations of the fossil, was also part of the research team and concludes: "It has taken us 23 years to get to this point. This is an exciting new chapter in Little Foot's history, and this is only the first paper resulting from her first trip out of Africa. We are constantly uncovering new information from the wealth of new data that was obtained. We hope this endeavour will lead to more funding to continue our work. Our team and PAST* emphasise that all of humanity has had a long-shared ancestry in harmony with the natural world, and that learning from those earliest ancestors gives us perspective on the necessity to conserve nature and our planet."
This paper is the first in what is expected to be a series of papers resulting from the wealth of data the Principal Investigators from the University of Witwatersrand in South Africa the University of Cambridge in UK, co-investigators from the Natural History Museum and Diamond were able to gain from their collaboration. Little Foot also underwent neutron imaging at STFC's ISIS Neutron and Muon Source at the same time as the work undertaken at Diamond Light Source, providing unprecedented access to complementary advanced imaging techniques. Neutrons are absorbed very differently from X-rays by the fossil's interior parts thanks to the sensitivity of neutrons to certain chemical elements. Despite having coarser spatial resolution, neutron tomography can sometimes differentiate between different mineralogical constituents for which contrast is very low for X-rays.
IMAGE: MLC ON THE TOP OF THE SHAFT AND LUCIA CASTAGNA, THE YOUNG ARCHAEOLOGIST OF GSB-USB THAT SECURED AND RECOVERED THE CRANIUM (ARCHIVE SABAP-BO/GSB-USB, PH. F. GRAZIOLI) view more
CREDIT: BELCASTRO ET AL, 2021, PLOS ONE (CC-BY 4.0, HTTPS://CREATIVECOMMONS.ORG/LICENSES/BY/4.0/)
A lone cranium in an Italian cave wound up there after being washed away from its original burial site, according to a study published March 3, 2021 in the open-access journal PLOS ONE by Maria Giovanna Belcastro of the University of Bologna, Italy and colleagues.
In 2015, archaeologists discovered a single human cranium (a skull without a lower jaw) in a gypsum cave in Northern Italy called Marcel Loubens cave. Caves are known to have been used for funerary practices in ancient Italy, but the fact that there are no other human remains in this cave has raised questions about how this skull came to be there, inspiring the researchers in this study to conduct a detailed analysis on the bone.
The structure of the bone indicates that it belonged to a woman between 24 and 35 years old at death. Carbon dating places the remains between 3630-3380 BC, during the Eneolithic period. Several lesions on the bone appear to be damage caused during the removal of soft tissues after death as part of a funeral ritual, while other damage and encrusted sediment on the bone are evidence that it was moved by natural processes not long afterward.
With this evidence, the researchers reconstructed the journey of the skull. After being treated and laid to rest in a burial place, the skull of this corpse rolled away, most likely moved by water and mud down the slope of a sinkhole and into the cave. Later, continued sinkhole activity created the modern structure of the cave, with this bone still preserved within. Besides revealing this fascinating story, this specimen also likely represents evidence of funerary treatment of a corpse in Italy during this time period.
The authors add: "An intriguing archaeological cold case: an isolated human cranium was found in the natural Marcel Loubens gypsum Cave (Bologna area, northern Italy) at the top of a vertical shaft, reached by an artificial 12-metre technical climb. How and when did it get there? Whose was it?
The cadaver (or head) of an early Eneolithic young woman was likely manipulated and dismembered in a funerary or ritual context and the skull, after a long and bumpy ride, accidentally ended up in the cave in the position in which it was found!"
Humans were present in Florida by 14,000 years ago, and until recently, it was believed the Bahamas - located only a few miles away - were not colonized until about 1,000 years ago. But new findings from a team including a Texas A&M University at Galveston researcher prove that the area was colonized earlier, and the new settlers dramatically changed the landscape.
Peter van Hengstum, associate professor in the Department of Marine and Coastal Environment Science at Texas A&M-Galveston, and colleagues have had their findings published in PNAS (Proceedings of the National Academy of Sciences).
Researchers generated a new environmental record from the Blackwood Sinkhole, which is flooded with 120 feet of groundwater without dissolved oxygen. This is important because it has pristinely preserved organic material for the last 3,000 years. Using core samples and radiocarbon dating, the team examined charcoal deposits from human fires thousands of years ago, indicating that the first settlers arrived in the Bahamas sooner than previously thought.
"The Bahamas were the last place colonized by people in the Caribbean region, and previous physical evidence indicated that it may have taken hundreds of years for indigenous people of the Bahamas - called the Lucayans - to move through the Bahamian archipelago that spans about 500 miles," van Hengstum said.
While people were present in Florida more than 14,000 years ago at the end of the last ice age, he said, these people never crossed the Florida Straits to nearby Bahamian islands, only 50 to 65 miles away. Meanwhile, the Caribbean islands were populated by people migrating from South American northward. Van Hengstum said the oldest archaeological sites in the southernmost Bahamian archipelago from the Turks and Caicos Islands indicate human arrival likely by 700 A.D.
"But in the northern Bahamian Great Abaco Island, the earliest physical evidence of human occupation are skeletons preserved in sinkholes and blueholes," he said. "These two skeletons from Abaco date from 1200 to 1300 A.D. Our new record of landscape disturbance from people indicates that slash-and-burn agriculture likely began around 830 A.D., meaning the Lucayans rapidly migrated through the Bahamian archipelago in likely a century, or spanning just a few human generations."
The team's other findings show how the Lucayans changed the new land.
When the Lucayans arrived, Great Abaco Island was mostly covered with pine and palm forests, and had a unique reptile-dominated ecosystem of giant tortoises and crocodiles. Increased deforestation and burning allowed pine trees to colonize and out-compete native palms and hardwoods.
Large land reptiles began to disappear after 1000 A.D. A significant increase in intense regional hurricane activity around 1500 AD is thought to have caused considerable damage to the new pine tree forests, as indicated by a decrease in pine pollen in the sediment core.
"The pollen record indicates that the pre-contact forest was not significantly impacted earlier in the record during known times when intense hurricane strike events were more frequent," van Hengstum said. "In our current world where the intensity of the largest hurricanes is expected to increase over the coming decades, the current pine trees in the northern Bahamas may not be as resilient to environmental impacts of these changes in hurricane activity."
IMAGE: 3D MODEL AND VIRTUAL RECONSTRUCTION OF THE EAR IN A MODERN HUMAN (LEFT) AND THE AMUD 1 NEANDERTAL (RIGHT). view more
CREDIT: MERCEDES CONDE-VALVERDE
BINGHAMTON, NY -- Neandertals -- the closest ancestor to modern humans -- possessed the ability to perceive and produce human speech, according to a new study published by an international multidisciplinary team of researchers including Binghamton University anthropology professor Rolf Quam and graduate student Alex Velez.
"This is one of the most important studies I have been involved in during my career", says Quam. "The results are solid and clearly show the Neandertals had the capacity to perceive and produce human speech. This is one of the very few current, ongoing research lines relying on fossil evidence to study the evolution of language, a notoriously tricky subject in anthropology."
The evolution of language, and the linguistic capacities in Neandertals in particular, is a long-standing question in human evolution.
"For decades, one of the central questions in human evolutionary studies has been whether the human form of communication, spoken language, was also present in any other species of human ancestor, especially the Neandertals," says coauthor Juan Luis Arsuaga, Professor of Paleontology at the Universidad Complutense de Madrid and co-director of the excavations and research at the Atapuerca sites. The latest study has reconstructed how Neandertals heard to draw some inferences about how they may have communicated.
The study relied on high resolution CT scans to create virtual 3D models of the ear structures in Homo sapiens and Neandertals as well as earlier fossils from the site of Atapuerca that represent ancestors of the Neandertals. Data collected on the 3D models were entered into a software-based model, developed in the field of auditory bioengineering, to estimate the hearing abilities up to 5 kHz, which encompasses most of the frequency range of modern human speech sounds. Compared with the Atapuerca fossils, the Neandertals showed slightly better hearing between 4-5 kHz, resembling modern humans more closely.
In addition, the researchers were able to calculate the frequency range of maximum sensitivity, technically known as the occupied bandwidth, in each species. The occupied bandwidth is related to the communication system, such that a wider bandwidth allows for a larger number of easily distinguishable acoustic signals to be used in the oral communication of a species. This, in turn, improves the efficiency of communication, the ability to deliver a clear message in the shortest amount of time. The Neandertals show a wider bandwidth compared with their ancestors from Atapuerca, more closely resembling modern humans in this feature.
"This really is the key," says Mercedes Conde-Valverde, professor at the Universidad de Alcalá in Spain and lead author of the study. "The presence of similar hearing abilities, particularly the bandwidth, demonstrates that the Neandertals possessed a communication system that was as complex and efficient as modern human speech."
"One of the other interesting results from the study was the suggestion that Neandertal speech likely included an increased use of consonants," said Quam. "Most previous studies of Neandertal speech capacities focused on their ability to produce the main vowels in English spoken language. However, we feel this emphasis is misplaced, since the use of consonants is a way to include more information in the vocal signal and it also separates human speech and language from the communication patterns in nearly all other primates. The fact that our study picked up on this is a really interesting aspect of the research and is a novel suggestion regarding the linguistic capacities in our fossil ancestors."
Thus, Neandertals had a similar capacity to us to produce the sounds of human speech, and their ear was "tuned" to perceive these frequencies. This change in the auditory capacities in Neandertals, compared with their ancestors from Atapuerca, parallels archaeological evidence for increasingly complex behavioral patterns, including changes in stone tool technology, domestication of fire and possible symbolic practices. Thus, the study provides strong evidence in favor of the coevolution of increasingly complex behaviors and increasing efficiency in vocal communication throughout the course of human evolution.
The team behind the new study has been developing this research line for nearly two decades, and has ongoing collaborations to extend the analyses to additional fossil species. For the moment, however, the new results are exciting.
"These results are particularly gratifying," said Ignacio Martinez from Universidad de Alcalá in Spain. "We believe, after more than a century of research into this question, that we have provided a conclusive answer to the question of Neandertal speech capacities."
A team of international researchers led by a Florida State University assistant professor has analyzed reams of data from the Neolithic to Late Roman period looking at migration patterns across the Mediterranean and found that despite evidence of cultural connections, there's little evidence of massive migration across the region.
"Because of the prevailing scholarly attitude of the 'connected' Mediterranean -- one with high degrees of mobility and migration that drive the archaeological patterns we see -- we'd imagined we'd see comparatively high levels of migration reflected in the strontium isotope data," said Thomas Leppard, assistant professor of anthropology at Florida State. "That instead we saw low levels of migration, and that these in fact decreased over time, was very surprising."
Leppard and his colleagues found that from about 7,500 BC to AD 500, migration rates ranged from about 6% to 9% of the population within the dataset. These rates seem to have decreased over time.
The research is published in the Journal of Mediterranean Archaeology.
Many historians and archaeologists consider the Mediterranean basin to have been interconnected for much of its history. However, that theory is largely built on material culture that suggests such connections - for example, Greek-looking pots in Sicily in the Late Bronze Age, Arabic coins in Medieval Sardinia, or Roman-style dining sets in 2nd century AD Portugal.
Leppard wondered if the same pattern would be obvious if they brought human biochemistry into the mix.
For several years, scientists have been able to understand individual life histories by analyzing the chemistry of human remains. In humans, bodily tissues, including most bones, remake themselves constantly so that their chemical composition reflects their current environment. However, dental enamel and a small skull bone called the petrous portion are extremely hard and don't remodel, so once a human reaches adulthood, the isotope ratios in those two areas of the body don't change.
"As a result, if you spend childhood somewhere, and then move as an adult to a different place with different underlying chemistry, we can see a difference in the chemistry - and critically in the ratios of different strontium isotopes - between your dental enamel and your other bones," Leppard said. "If, however, you grew up and died in the same location, the ratios will be the same. That means we can start to quantify percentages of locals, and percentages of nonlocals in a given area."
Archaeologists have employed this technique for a while in the Mediterranean, but the sample sizes are generally very small because the experiments are expensive and there often aren't many samples of human remains. Leppard and his colleagues compiled all the data from many smaller experiments capturing a large time frame and re-analyzed it.
He cautioned that this is a starting place to assess the migration patterns of this region.
"It's important to say that migration is only one aspect of human mobility; we can't access seasonal or habitual mobility with this method, for example," Leppard said. "That said, we thought this would be a powerful method for assessing large-scale trends in Mediterranean migration across time. That these trends don't really match the current scholarship should generate productive debate and prompt new research."
