Geoarchaeology and the search for the first Americans

Research into the origins and subsequent development of the first American cultures (“Paleoindians”), in particular the timing and place of their arrival, has provoked heated, contentious debates in North American archaeology since the 19th century. Many of the questions in this archaeological puzzle are fundamentally geological and thus many of the answers have come from the geosciences, including geology, geography, and soil science, and at a wide range of spatial scales. Stratigraphy, perhaps the most basic principle in both archaeology and geology, first established the antiquity and chronology of the earliest artifact assemblages at sites such as Folsom and Clovis in New Mexico by demonstrating clear association of artifacts and Pleistocene fauna. Geologists and paleontologists further provided age estimates of sites in the absence of other forms of numerical age control. Geologists also were prominently involved in developing the radiocarbon method and applying it to Paleoindian sites. Many Paleoindian sites also yielded not only extinct fauna, but stratigraphic records with evidence of markedly different depositional environments in the past. These sites were inviting to geologists because many investigators had backgrounds in Pleistocene paleontology. The ancient fauna and the striking contrasts between past and present depositional environments drew the attention of archaeologists and earth scientists alike who recognized the paleoenvironmental implications. At regional, subcontinental scales the peopling of the New World has been a question revolving around lowered seas levels and fluctuating glacier margins. Modeling sea-level changes and the paleogeography of the “Bering Land Bridge” and the high-precision dating of ice retreat over Canada is helping to understand the environmental conditions faced by Native American forbears in Beringia and the environment, route(s), and timing of their entry into North America.     

Influence of drought stress and low irradiance on plant water relations and structural constituents in needles of Pinus ponderosa seedlings

The influence of low light on tolerance to prolonged drought was tested on unshaded and shaded seedlings of ponderosa pine (Pinus ponderosa var. scopulorum Dougl. ex Laws.). Unshaded seedlings of P. ponderosa var. ponderosa were also drought stressed to compare varietal responses to drought. The maximum irradiance received by shaded seedlings was 10% of full light. Seedlings were progressively drought stressed until predawn water potentials (Psi(x)) were -5.0 MPa. Relative water content (RWC) and the reciprocal of Psi(x) were analyzed by means of an unusual application of the pressure-volume relationship for determination of RWC of the apoplast (RWC(a)), osmotic potential at full turgor (Psi(oft)), and ratio of fully turgid weight to dry weight. Major varietal differences in drought response were in RWC(a) and needle cellulose content. The shaded seedlings showed tissue damage at relative water contents < 60%, and were killed by water deficits from which unshaded seedlings recovered. Correspondingly, shaded plants had significantly higher cell volume/cell mass ratio, Psi(oft), less cellulose in needle tissue, and lower RWC(a) than unshaded plants. These differences suggest that low irradiance restricts drought adaptation in ponderosa pine.     

Corticosteroid-induced suppression of in vitro lymphocyte proliferation in four captive rhinoceros species.

Captive African black rhinoceroses (Diceros bicornis) are unusually susceptible to several diseases not commonly observed in any of the other three rhinoceros species maintained in captivity. The potential role of corticosteroids (either endogenously produced or exogenously administered) in the development of these sometimes fatal diseases has been questioned. In this study, the suppressive effects of two therapeutic corticosteroids (dexamethasone and hydrocortisone) on in vitro lymphocyte proliferation was examined in four rhinoceros species, including the Sumatran rhinoceros (Dicerorhinus sumatrensis, n = 3), Indian rhinoceros (Rhinoceros unicornis, n = 4), African black rhinoceros (n = 10), and African white rhinoceros (Ceratotherium simum, n = 5). Three blood samples collected from each rhinoceros 1 mo to 1 yr apart provided replicates for the study. Both dexamethasone and hydrocortisone suppressed (P < 0.05) lymphocyte proliferation stimulated by B-cell mitogens (pokeweed and lipopolysaccharide) and T-cell mitogens (phytohemagglutinin and concanavalin A). Suppressive effects of the glucocorticoids differed (P < 0.05) depending on the mitogen used to stimulate the lymphocytes. Overall, dexamethasone was a more potent suppressor of cell proliferation when compared with hydrocortisone (P < 0.05). However, black rhinoceros cell proliferation in response to any of the four mitogens was never completely suppressed, even in cultures containing the highest steroid concentration tested (10(-3) M). The effect of the two corticosteroids differed slightly among the rhinoceros species and subspecies tested, but there was no evidence that eastern or southern black rhinoceros lymphocytes were more sensitive to the suppressive effects of corticosteroids than the other rhinoceros species.     

Homing behavior, orientation, and home range of salamanders tagged with tantalum-182

Using radioactive tags, we recorded movements of salamanders (Plethodon jordani) in their home areas and during homing. Males occupied home areas about three times larger than those of females and made occasional excursions into outlying regions. Homing after 22-to 60-meter displacements was direct and rapid, once initiated. Course headings at 1 meter from release were random; those at 2 meters and more were home-oriented. Males initiated homing movements sooner than females, although both sexes traveled at similar rates. Increased incidence of climbing on vegetation after displacement suggests olfactory mechanisms of orientation. These observations give direct evidence of homing orientation in caudate amphibians.     

Assessment of Resting Insulin and Leptin Concentrations and Their Association With Managerial and Innate Factors in Horses

The purpose of this study was to determine how insulin and leptin concentrations varied in a large population of privately owned horses. Further, the study was designed to examine the relationships between insulin and leptin with innate (sex, age, breed) and managerial (diet, exercise) factors in these horses. Resting blood samples (for determination of glucose, insulin, and leptin concentrations), body condition scores, feed information, and health history were collected from 366 privately owned horses. In this group of horses, 48% were considered overweight (Body Condition Score ≥6) and 8% were considered hyperinsulinemic (insulin concentrations >30 μU/mL). Confirming the findings of studies within research herds, both insulin and leptin concentrations were found to be correlated with body condition score (P < .001). It was also found that geldings had higher insulin concentrations than mares (P < .05). Ponies were found to have higher insulin and leptin concentrations as well as higher body condition scores, than several other breeds examined. While not a specific measure of insulin sensitivity, resting insulin concentrations have been associated with quantitative measurements of insulin sensitivity and may be useful in large-scale studies for estimating insulin and glucose dynamics. Because of the association between insulin resistance and obesity with diseases such as laminitis, the findings of the present study may help owners identify horses that may be at risk for the development of such conditions.