Sowing the seeds of future research: Data sharing, citation and reuse in archaeobotany

Lay summary authored by Lisa Lodwick. The full article can be read in Open Quaternary: http://doi.org/10.5334/oq.62

Archaeobotanists spend countless hours at the microscope, sorting and identifying ancient plant remains. Counting seeds is a key step in the research process, enabling patterns to be established across sites, within regions, and through time – patterns that can tell us about a wide range of past human-plant relationships. As the number of archaeobotanical data sets have grown and statistical analysis has become more widely used, meta-studies have provided new insights into the timing of crop domestication, the spread of domesticated plants, and shifts in how crops were cultivated. Undertaking such meta-analysis relies on access to the counts of plant remains from the initial studies. However, there is a common perception that much data produced within archaeology, and across many academic disciplines, is not always made publicly available. How much seed count data is still available?

In this study, I used over 200 journal articles published over the last decade in 16 journals to assess how archaeobotanists are currently sharing their data. Whilst 56% of papers did provide their full or ‘raw’ data, this was often in forms that make the reuse of this data challenging – e.g., the data might need re-entering into a spreadsheet. The remaining articles did not contain their ‘raw’ data, limiting the types of analysis for which they could be used. A second assessment was undertaken of meta-studies using previously published archaeobotanical data – whilst 64% did reference the studies used, 21% did not, hindering the extent to which others can build on these studies in the future. The lack of formal credit, by way of citation, to data producers for the creation of archaeobotanical datasets may limit the motivation to make future datasets available in a reusable format.

The decisions researchers make regarding if and how to share datasets is complex, with factors including career stage, access to financial and technological resources, education and training all coming into play. But discussions of data-sharing should be undertaken across academic communities, and training should be provided as part of degrees and within professional bodies; after all, the availability of sample-level data enables the fullest future use of archaeobotanical research, and makes the most of long hours spent at the microscope.

Based on the article:
Lodwick, L., 2019. Sowing the Seeds of Future Research: Data Sharing, Citation and Reuse in Archaeobotany. Open Quaternary, 5(1), p.7. DOI: http://doi.org/10.5334/oq.62

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Cool Hyenas

Lay summary authored by Jack Tseng. The full paper can be read in Open Quaternary: http://doi.org/10.5334/oq.64

Beringia, the geographic region including parts of eastern Russia, Alaska, and western Yukon Territory, is scientifically important for understanding animal and human movements in and out of North America. Our current understanding of Ice Age fossil records in Beringia suggests that the region had a higher diversity of predatory mammals than at the present. However, fossils of large predator mammals are exceedingly rare, making a more complete understanding of why some species went extinct, whereas other survived, difficult.

Old Crow flats_(photo by Dr Duane Froese 2004)

Aerial view of the Old Crow River meandering through Old Crow Flats (Photo by Duane Froese).

The Old Crow region of northwestern Yukon Territory contains one of the richest Ice Age fossil deposits in Beringia and north of the Arctic Circle. The presence of Ice Age fossils has been known to First Nations people for hundreds of years. In the past century, more than 50,000 fossil specimens have been systematically collected from the Old Crow. Out of these specimens, we describe two fossils that belong to one of the rarest predators in the Beringian region, that of hyenas.

The hyena fossils we describe in this study belong to Chasmaporthetes, which is a group of wide-ranging predators known for their running-adapted limb characteristics. Prior to our study, Chasmaporthetes fossil sites between Asia and North America span more than 10,000 km, from Mongolia to southern United States. Although a Beringian route has been hypothesized for these hyenas, no physical evidence of the presence of Chasmaporthetes existed until this study confirmed two fossilized Chasmaporthetes teeth from the Old Crow. We can now say that a Beringian immigration route of Chasmaporthetes from Asia to North America is supported by the intermediate locale of Old Crow, north of the Arctic Circle.

IMG_2280

A large pile of fossil mammal bones and teeth collected from the Old Crow Basin (Photo by Grant Zazula).

The success of Chasmaporthetes in spreading throughout the world’s northern continents is evident from fossil records in Europe, Africa, Asia, and North America. However, the limited time duration of Chasmaporthetes in North America suggests that other predators may have competed with them there, preventing them becoming dominant. Our review of candidate competitor species indicates that giant short-faced bears and precursors of modern wolves may have been the most likely competitors of Chasmaporthetes in certain geographic regions of North America.

The extinction of Chasmaporthetes during the Pleistocene marked the end of running-adapted hunter-scavengers on the North American continent. Given the importance of scavengers to modern day African ecosystems, we speculate that the extinction of Chasmaporthetes may have changed the way the North American food webs functioned during the later Pleistocene, and into today.

Full paper: Tseng, Z.J., Zazula, G. and Werdelin, L., 2019. First Fossils of Hyenas (Chasmaporthetes, Hyaenidae, Carnivora) from North of the Arctic Circle. Open Quaternary, 5(1), p.6. DOI: http://doi.org/10.5334/oq.64

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Birds in Medieval Norway

This gallery contains 2 photos.

Lay summary authored by Samuel Walker. The full paper can be read in Open Quaternary: http://doi.org/10.5334/oq.58 Norway is home to over 500 bird species, with around 259 of these breeding in Norway. Recent ornithological work has shown that 22% of … Continue reading

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Where There’s Fire, There’s Smoke: The Significance of Air Circulation and Hearth Location at Paleolithic Cave Sites

Lay summary authored by Yafit Kedar. The full paper can be read in Open Quaternary: http://doi.org/10.5334/oq.52

Hearths are pivotal element in understanding the organization of space of human behavior in Paleolithic caves and rockshelter sites. While fire provided cooking facilities, warmth and light, one of the major negative products fire is smoke, which has an immediate effect on humans and may even prevent cave occupation after a short period. In this paper, we showed that hearth location and season of use are not randomly determined and can be explained using the air circulation model. The model is based on data developed by the NIST (USA), for simulating fire in closed spaces such as buildings and compartments. Smoke height can be estimated according to air circulation parameters in the cave, taking into account hearth location, size and season of use. We show that the expected smoke levels in cold season are higher than the smoke level in warm season. In addition, we showed that the preferred hearth location is near the back wall and not at the cave entrance.

Yafit hearths

Example of cave air circulation in caves in different conditions: a– example of cave air circulation in winter. b– example of a hearth in the cave’s depth during the winter season. Smoke is emitted towards the ceiling in the direction of the cave opening. c– example of the effect of hearth location at the cave’s entrance on the internal air circulation. d– example of the effect of a chimney with a hearth located at the cave’s back wall. The arrows represent air circulation, and the broken line represents the balance point between the cold and hot air flows (Figure Credit: Yafit Kedar).

Our short survey of sites has also revealed that numerous hearths were used in Paleolithic rockshelters, such as in Abric Romani and To Faraj, as opposed to single ones at caves. In rokshelters, hearths seem to represent group activity area enabled by the large entrance space characteristic of rockshelters allowing smoke to disperse quite rapidly. This is in contrast to caves, where smoke emitted from the hearth was present lower height and thus might have had an immediate effect on the occupants. Paleolithic caves are therefore expected to contain fewer hearths, located towards the back, as suggested by our study.

Our preliminary analysis suggests that cave hearths were better suited for cold season use, when heat from the fire increased the temperature difference between the cave’s interior and the external environment, resulting in faster air circulation and more efficient smoke ventilation. During the hot season, when the internal and external temperature difference is smaller, smoke ventilation is poorer. This would have led to a higher concentration of smoke in the cave and a lower smoke height, making habitation difficult. For example, Lazaret Cave and Tor Faraj rockshelter had a few small hearths in the cave’s depth with faunal and botanical remains indicating winter habitation.

Since hearths emit a great deal of smoke, it would seem that early humans must have reasoned about air circulation when positioning a hearth within a cave, in order to benefit from its many advantages.

Full Paper: Kedar, Y. and Barkai, R., 2019. The Significance of Air Circulation and Hearth Location at Paleolithic Cave Sites. Open Quaternary, 5(1), p.4. DOI: http://doi.org/10.5334/oq.52

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Data compilation describes the demise of a North American ice sheet

Lay summary authored by Joel Gombiner. The full paper can be read in Open Quaternary: http://doi.org/10.5334/oq.55

The last global climate transition occurred between 20,000 and 10,000 years ago, as the earth warmed from the last ice age into the milder Holocene epoch. In western North America, this climate transition included melting and retreat of the Cordilleran Ice Sheet, a continental ice mass that was similar in size to the modern Greenland Ice Sheet. The Cordilleran Ice Sheet covered much of western North America, extending from Washington to Alaska.

Gombiner

Map showing study sites and extend of Laurentide and Cordilleran Ice Sheets. Credit: J. Gombiner.


This new data paper focuses on the retreat of the southern Cordilleran Ice Sheet. The paper describes a compilation of previously published radiocarbon ages, which will be downloadable as a spreadsheet or text file on the Open Quaternary Dataverse. The compilation contains over 60 post-glacial radiocarbon ages from 36 separate scientific papers. This geo-referenced age data describe the approximate timing of when specific locations in the region became ice-free. The regional pattern of deglaciation might help researchers to understand the interplay of factors that caused the ice sheet to retreat, such as warming of the ocean and atmosphere, increasing summer sun intensity, and rising sea level. Additionally, the retreat of the Cordilleran Ice Sheet likely set the stage for human migration into North America.

The compilation is meant to be a starting point for researchers studying the Pacific Northwest during the last deglaciation. It is not the complete picture of deglaciation, as each sample in the compilation requires interpretation and careful consideration, and the compilation highlights areas where there is not much data. It is also not the first compilation of post-glacial radiocarbon ages for this region. I relied heavily on previous compilations in assembling this new one, but also discovered additional ages in geologic maps, palynology studies, and other articles. Some journal articles were not available online, and I thank the UW Libraries scanning service for finding and scanning those articles. I hope this data will be a helpful tool for other Quaternary researchers focusing on the southern Cordilleran Ice Sheet.

Read the paper here:

Gombiner, J., 2019. Post-Glacial Radiocarbon Ages for the Southern Cordilleran Ice Sheet. Open Quaternary, 5(1), p.3. DOI: http://doi.org/10.5334/oq.55

and access the dataset here:

https://dataverse.harvard.edu/dataset.xhtml?persistentId=doi:10.7910/DVN/YGRESZ

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Teeth ‘heal’ at different rates among primate species

Lay summary authored by Ian Towle. The paper can be read in Open Quaternary: http://doi.org/10.5334/oq.48

It is well known that the outer layer of a tooth, enamel, can’t repair after it has been removed through injury, wear or a cavity. However, the underlying dentine can ‘heal’ to a certain extent, in the form of new material formation called tertiary dentine. This form of dentine forms in response to disease and wear to protect the underlying pulp chamber, and therefore ultimately protects the individual against abscesses and infection.

Gorrilla mandible Ian Towle

Gorilla mandible showing extensive tertiary dentine formation (Credit: I. Towle)

Tertiary dentine can be easily distinguished on the surface of a tooth, with its much darker appearance compared to the original dentine. It is not known if certain species have evolved to produce tertiary dentine in response to stimuli sooner, or at a quicker rate, than others.

The aim of this study was to begin to address this question by comparing the frequency of tertiary dentine in different species of primate, and to see if some species produce this material quicker than others in response to wear.

The results show that gorillas have by far the highest rate of tertiary dentine formation, with over 90% of teeth with dentine exposed through wear showing tertiary dentine. Gorillas likely evolved this high rate as protection against heavy wear, with early/more tertiary dentine formation keeping the tooth functioning for longer.

In contrast, hominins (humans and our closely related fossil relatives), exhibit a remarkably low and uniform rate of tertiary dentin formation, with all species showing a frequency of around 15%. Chimpanzees fall between these extremes, with 47% of worn teeth showing ‘healing’. Why humans and our close relatives produce tertiary dentine slower and/or later than other great apes is not known, but it may be because we evolved different ways to cope with heavy wear and dental disease, such as evolving thick enamel, or it may instead relate to dietary and behavioural differences.

No letters or arrows Ian Towle_top row

From left to right: Pan troglodytes lower right deciduous central incisor (specimen MER ii 27); Paranthropus robustus lower right central incisor (specimen SKX 3559); Gorilla gorilla gorilla lower left first premolar (specimen M 786) (Credit: I. Towle)

When more species have been studied it will be possible to give further insight into what drives tertiary dentine formation on an evolutionary scale. If, as seems likely, diet plays a crucial role, then the presence of this material in the fossil record may be useful for reconstructing diet in extinct species.

Read the paper here:

Towle, I., 2019. Tertiary Dentine Frequencies in Extant Great Apes and Fossil Hominins. Open Quaternary, 5(1), p.2. DOI: http://doi.org/10.5334/oq.48

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Reading the (Mormon) tea leaves at the bottom of packrat nests tells the story of Late Quaternary climate change in Western North America

Lay summary authored by Robert Harbert. Their full paper can be read in Open Quaternary: http://doi.org/10.5334/oq.46

During a 1980 episode of Cosmos Carl Sagan said “You have to know the past to understand the present.”2 For those of us who study geographic distributions of plants it is clear that the plant fossil record can tell us a lot about how ecosystems have changed through Earth’s history. By studying the shifts in where certain plants occur during different climatic periods we can begin to understand how present-day ecosystems may respond to anthropogenic climate change.

In this study we take this reasoning and invert it. The present can inform our understanding of the past. By taking data on the distribution of plant species today from the Global Biodiversity Information Facility (GBIF) and combining those with current climate models we can build a predictive model for climate based on local plant communities. We call this modeling protocol CRACLE (Climate Reconstruction Analysis using Coexistence Likelihood Estimation).

Here we apply CRACLE to the estimation of climate from Western North America over the past ~50,000 years. We are able to do this due to a combination of the fact that packrats (Neotoma spp.) are compulsive hoarders of plant twigs, fruit, leaves, and seeds and the arid climate preserves plant material in packrat nests (also called ‘middens’) for thousands of years. By analyzing samples of these plants from a range of time throughout this region we are able to piece together the climate history of Western North America as recorded through the changing distributions of plants.

Maker:L,Date:2017-8-31,Ver:5,Lens:Kan03,Act:Kan02,E-Y

A 14,600 year old fossilized packrat (Neotoma spp.) midden from Northern Baja California, MX. Numerous plant fragments, packrat dung, and small stones visible embedded in the matrix. Visible twigs, leaves, and seeds likely include Juniperus californica, Agave, Artemisia, Ephedra, and various cacti, composites, and grasses. Credit: R. Harbert

Our climate record shows that Western North America was 4-6°C cooler during the Last Glacial Maximum (LGM — 26-19ka) with the most pronounced departure from modern climatological averages coming during the warmer months. We also calculate that the rapidly warming climate of the period just after the LGM shows warming at a rate that is approximately 10 times slower than what is predicted for the next 100 years. During past warming periods, as glaciers melted, species migrated north in step with the changing climate, but species today must contend with climate change occurring at a rate not seen in at least the last 50 millenia. Whether or not migration will happen fast enough to prevent mass extinctions in our future remains to be seen as we find no analog for this rate of change in the packrat midden fossil record.

This record fills in a substantial gap in the terrestrial paleoclimate record of Western North America and represents a novel source of data. Many thousands more samples of fossilized packrat middens exist and are being studied. As we know more about where plants lived in the past we will be able to use CRACLE modeling to build more detailed and robust reconstructions of paleoclimate for this region.

Footnotes:
Title: ”Mormon Tea” is a common name for the plant genus Ephedra, a common component of packrat midden macrofossil assemblages.
2Sagan, C. E. (author and presenter). (1980) Episode 2: One Voice in the Cosmic Fugue [Television series episode]. In Adrian Malone (Producer), Cosmos: A Personal Voyage. Arlington, VA: Public Broadcasting Service.

Read the full paper:

Harbert, R.S. and Nixon, K.C., 2018. Quantitative Late Quaternary Climate Reconstruction from Plant Macrofossil Communities in Western North America. Open Quaternary, 4(1), p.8. DOI: http://doi.org/10.5334/oq.46

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