Utilizing inquiry-driven science outreach to curate Natural Trap Cave fossils and inspire the pursuit of STEM careers

Despite the rising emphasis on STEM (science, technology, engineering, and mathematics) education in the last two decades, the United States has seen little change in student performance, based on international assessments. Transforming science education from the more traditional, lecture-format classes to inquiry-driven exercises is central for improving student’s STEM literacy and competency at all grade levels. This paper describes an outreach program that was developed for upper-level U.S. high school students (10th–12th grade) and centers around hands-on, inquiry-driven exercises using the large-bodied (> 3 kg) mammalian fossils from Natural Trap Cave (NTC). The objectives of this program were for the students to develop an understanding of the morphological adaptations of the vertebrate skeleton, preservational biases in the fossil record, and to participate in each of the curatorial steps used for the long-term preservation of fossils. Students from Des Moines Public School Central Campus came to Des Moines University 2 hours a week for a semester, receiving high school and community college credit for participating. The NTC outreach program has been offered for 11 semesters since the fall of 2014. Thirty-four high school students have participated, consisting of 24 women and 10 men, with 19 of the students belonging to African American, Middle Eastern, Asian, and Hispanic ethnicities. The students helped to identify and curate 3,700 NTC fossil specimens. Several of the students presented posters on the work they did during this outreach program at the multiple district and state science fairs in Iowa and received accolades. Only the 2017–2019 students were surveyed, but all the students reported gaining a deeper understanding of the scientific process and the utility of paleontology. One student even reported changing their career goal from undecided to a STEM field. The framework developed for the NTC outreach program can be easily modified to fit the needs or structure of another research project, community partnership, science laboratory, or museum facility, with the target audience being students from middle school to undergraduate. This type of STEM outreach program can also help improve scientific literacy and generate much-needed excitement and interest in science, at a time when many students are exploring potential career paths.

An age-depth model and revised stratigraphy of vertebrate-bearing units in Natural Trap Cave, Wyoming

Almost a half-century ago excavations at Natural Trap Cave (NTC) began to yield evidence of the steppe paleoecology along the western slope of the Bighorn Mountains in north central Wyoming. The first decade of fieldwork led to the discovery of a diverse fauna that existed at the end of the Last Glacial Maximum. Stratigraphic deposits below the entrance of the cave were studied soon after excavations began, but never formally published. Although stratigraphy, taphonomy, and depositional circumstances were briefly discussed over the following years, little has been done to correlate the numerous stratigraphic schemes used by various authors. In this study, four stratigraphic sections were measured and analysed to establish an easily modifiable lithostratigraphic system of nomenclature. We provide the first correlations of all stratigraphic nomenclature used throughout excavations at NTC to facilitate comparisons with current and previous collections and publications. By leveraging more than 100 radioisotopic dates we developed an age-depth model and chronostratigraphic framework to further interrogate spatiotemporal relationships between strata, paleoenvironmental proxies, and fossil assemblages. Deposition is shown to be discontinuous; sediment accumulation in the study area is restricted to the buildup through peak penultimate and Last Glacial maxima. More recent (<10 ka) Holocene deposits unconformably cover the eroded surface of underlying Pleistocene strata. There is active reworking of sediments with transport and deposition of reactivated sediments within the Lower Chamber. We note that the two hiatuses coincide with interglacial periods and may reflect changing depositional circumstances within the cave such as extended periods of non-deposition, erosion, or bypass (possibly leading to deposition in the Lower Chamber). Contrary to previous reports, we demonstrate that it is unlikely a prominent snow cone existed or contributed to the pattern of sediment and fossil distribution within the study area, furthermore, we do not observe a continuous Pleistocene-Holocene transition in the study area. Further stratigraphic work will be needed to better understand the interrelationship between Main and Lower chamber deposits and the evolution of sediment accumulation in NTC.

THE AMVROSIIVKA BISON BONE BED AND FEATURES OF ITS USE

The Amvrosiivka Upper Palaeolithic complex, composed of a camp site and nearby bison bone bed is located in the Donetsk oblast’, at the top of the Kazenna ravine, a right tributary of the Krynka river, which drains into the Mius river. The site is dated by an average of 19000—18000 uncal BP and belong to Epigravettian tradition. The results of the long-term research the Amvrosiivka bison bone bed was analyzed in the article. The features of topography (a gully-terrace on board of a ravine), planigraphy, stratigraphy of a bone bed (the ledges-thresholds and some sterile layers in cultural remains distribution), and also the seasons of the kill of animals (alternative, with prevalence of cold) was summarized. Data about the bison bones (Bison priscus, MNI = 650 and bones with cultural modifications) is presented. The prevalence of the hunter projectile weapon details (27 bone points and about 90 flint micropoints-inserts), and also flint tools for butchering animals among the archaeological finds is determined. The interpretation of the bone bed at the same times was controversial: as a refuse dump near dwelling (Evseev), as a resulted from a one-time (Pidoplichko) or repeated (Efimenko) mass drive of bison, or as a ritual locale (Boriskovskij). At present the site is interpreted as a place of numerous mass drive of bison and, mainly, primary butchering of hunting bag, and also, probably, storages of meat products in the form of the frozen carcasses of bison in a cold season (Krotova, Snizhko, Julien). The ethnoarchaeological data about methods of collective kills by Paleoindian and Indian pedestrian hunters on bison of the North America (Frison 2004) for the reconstruction of possible variants of the mass drive of bison in Amvrosiivka is used. The conclusion is made that for the purpose organization of the series of mass drive of bison at different seasons the hunters in Amvrosiivka used a natural trap — the gully-terrace on a board of ravine — the right tributary of a Kazenna ravine. This terrace with one abrupt and rather high (4—5 m) board, obviously, used for a drive of bison from above, a plateau (method of «jump») that the hunters, obviously, at a certain stage having added with the restraining structure (pens) which should keep the escaped and wounded animals. The variant of a possible shelter from below, a thalweg of the Kazenna ravine (an «arroyo trap» method) also is not excluded.

Yucatán carnivorans shed light on the Great American Biotic Interchange

The Great American Biotic Interchange is considered to be a punctuated process, primarily occurring during four major pulses that began approximately 2.5 Ma. Central America and southeastern Mexico have a poor fossil record of this dynamic faunal history due to tropical climates. Exploration of submerged caves in the Yucatán, particularly the natural trap Hoyo Negro, is exposing a rich and remarkably well-preserved late Pleistocene fauna. Radiometric dates on megafauna range from approximately 38 400–12 850 cal BP, and extinct species include the ursid Arctotherium wingei and canid Protocyon troglodytes . Both genera were previously thought to be indigenous to and confined to South America and appear to represent an instance of large placental mammals, descended from North American progenitors, migrating back north across the Panama Isthmus. This discovery expands the distribution of these carnivorans greater than 2000 km outside South America. Their presence along with a diverse sloth assemblage suggests a more complex history of these organisms in Middle America. We suggest that landscape and ecological changes caused by latest Pleistocene glaciation supported an interchange pulse that included A. wingei , P. troglodytes and Homo sapiens .