To evaluate a model of the travel-route selection process for upper Ohio Valley Paleoindian foragers (13,500–11,400 cal BP), this study investigates archaeological data through the theoretical framework of landscape learning and risk-sensitive analysis. Following initial trail placement adjacent to a highly visible escarpment landform, Paleoindians adopted a risk-averse strategy to minimize travel outcome variability when wayfaring between Sandy Springs, a significant Ohio River Paleoindian site, and Upper Mercer–Vanport chert quarries of east-central Ohio. Although a least-cost analysis indicates an optimal route through the lower Scioto Valley, archaeological evidence for this path is lacking. Geomorphic and archaeological data further suggest that site absence in the lower Scioto Valley is not entirely due to sampling bias. Instead, evidence indicates that Paleoindians preferred travel within the Ohio Brush Creek–Baker's Fork valley despite its longer path distance through more rugged, constricted terrain. Potential travel through the lower Scioto Valley hypothesizes high outcome variability due to the stochastic nature of the late Pleistocene hydroregime. In this case, perceived outcome variability appears more influential in determining travel-route decisions among Paleoindians than direct efforts to reduce energy and time allocation.

Recent reexamination of pottery, copper objects, and glass trade beads using modern analytic methods has amended the occupational history of the Cloudman site (20CH6), once interpreted as an early “Contact” period site in Michigan. The original chronology of the site, located on northern Michigan's Drummond Island in Lake Huron, was based on an apparent association of Iroquoian pottery with European-made trade goods relatively dated to circa AD 1630. Current advances in archaeological dating methods have revealed new insights into the poorly understood settlement patterns and social interactions of various Upper Great Lakes groups between AD 1300 and 1700. Accelerator mass spectrometry dating of carbonized food residue collected from late Late Woodland and Ontario Iroquoian pottery vessels suggests some contemporaneous use of both styles and the culmination of occupation by pottery-making groups by AD 1500. Elemental analysis of glass beads indicates that the recovered trade items were likely manufactured post–AD 1650. Likewise, compositional analysis of copper-base metal artifacts clarifies how such objects were made and used over time at the site. The results demonstrate how the application of modern analytic methods to curated collections can lead to significant reinterpretation, ultimately enhancing understandings of regional chronologies, social relationships, and population movements.

A paleoenvironmental time-series spanning the Holocene was constructed using 29 radiocarbon ages and 149 standardized δ13Csom values from alluvial terrace profiles along the middle Delaware River valley. There is good agreement between increasing δ13Csom and Panicoideae phytolith concentrations, suggesting that variations in C4 biomass are a major contributor to changes in the soil δ13C. A measurement error deconvolution curve over time reveals two isotope stages (II–I), with nine sub-stages exhibiting variations in average δ13Csom (average %C4). Stage II, ~ 10.7–4.3 ka, shows above-average δ13Csom (increase %C4) values with evidence of an early Holocene warming and dry interval (sub-stage IIb, 9.8–8.3 ka) that coincides with rapid warming and cool-dry abrupt climate-change events. Sub-stage IId, 7.0–4.3 ka, is an above average δ13Csom (increase %C4) interval associated with the mid-Holocene warm-dry hypsithermal. The Stage II–I shift at 4.3 ka documents a transition toward below average δ13Csom (decrease %C4) values and coincides with decreasing insolation and hydroclimatic change. Sub-stages Ib and Id (above average %C4) coincide with the first documented occurrence of maize in the northeastern USA and a substantial increase in human population during the Late Woodland. These associations suggest that people influenced δ13Csom during the late Holocene.

Late glacial scenarios of ice retreat and biogeography databases constrain the dispersal routes of obligate freshwater fishes into Atlantic Canada and Maine. Evidence indicates glacial ice covered the present-day mainland and offshore islands at 18,000 14C yr before present. Possible refugia for extirpated freshwater fishes were the exposed outer edge of the Grand Banks (east), exposed Georges Bank (south-Atlantic Refugium), and the Mississippi Refugium in the west. It is improbable that the region was recolonized from the offshore refugia. Rather, fishes recolonized from the east via the upper St. Lawrence River valley into the upper Saint John River, Maine (Lake Madawaska) from 11,000 to 12,000 14C yr BP. The short period of entry resulted in the low diversity of obligate freshwater species in the region. Lake Madawaska was breached and dispersal continued into the remainder of the region after 8000 14C yr BP. By 6000 14C yr BP, access routes to the east along low-lying coastal zones were blocked by rising sea levels, which isolated Prince Edward Island, Cape Breton Island, and most probably Nova Scotia. Natural dispersal across the region appeared complete by this time.

The modern analog technique typically uses a distance metric to determine the dissimilarity between fossil and modern biological assemblages. Despite this quantitative approach, interpretation of distance metrics is usually qualitative and rules for selection of analogs tend to be ad hoc. We present a statistical tool, the receiver operating characteristic (ROC) curve, which provides a framework for identifying analogs from distance metrics. If modern assemblages are placed into groups (e.g., biomes), this method can (1) evaluate the ability of different distance metrics to distinguish among groups, (2) objectively identify thresholds of the distance metric for determining analogs, and (3) compute a likelihood ratio and a Bayesian probability that a modern group is an analog for an unknown (fossil) assemblage. Applied to a set of 1689 modern pollen assemblages from eastern North America classified into eight biomes, ROC analysis confirmed that the squared-chord distance (SCD) outperforms most other distance metrics. The optimal threshold increased when more dissimilar biomes were compared. The probability of an analog vs no-analog result (a likelihood ratio) increased sharply when SCD decreased below the optimal threshold, indicating a nonlinear relationship between SCD and the probability of analog. Probabilities of analog computed for a postglacial pollen record at Tannersville Bog (Pennsylvania, USA) identified transitions between biomes and periods of no analog.

In this paper we use radiocarbon dates to evaluate the signature of the Younger Dryas Chronozone (YDC) in eastern North America. Using an approach that examines radiocarbon dates by region, we argue that the northeastern United States shows a better overall representation of radiocarbon dates when compared to the Mid-Atlantic and Southeast. These data result in a peak in summed probability distributions during the YDC, which is often interpreted as evidence of population growth. Further examination of these distributions, however, illustrates that differential standard deviations, varying sample size, and the effect of taphonomic and research biases likely overwhelm any demographic signatures in our study sample. Consequently, the frequency of radiocarbon dates by itself is insufficient for understanding the relationship between climate, culture and demography in eastern North America.

In our ongoing study of the genus Cladonia, we have encountered several specimens that have proved to represent undescribed species. Four of them are described here as new. Cladonia camerunensis (Cameroon) resembles C. didyma (Fée) Vain., but the former has a coarsely granular surface and a melanotic podetial base; C. compressa (Bolivia) is distinguished by a dominant primary thallus and deeply divided and phyllopodiate podetia; C. longisquama (Seychelles) has well-developed squamules and contains barbatic acid; C. vescula (Bolivia, Peru) differs from C. peziziformis (With.) J. Laundon by an ecorticate podetial surface and the production of homosekikaic acid. The names C. aspera Ahti & Kashiw. and C. crinita (Delise ex Pers.) Ahti are shown to be illegitimate later homonyms and are replaced by the names C. asperula and C. perfoliata, respectively. The neglected name C. botryoides (Tuck.) Vain. is shown to be a synonym of C. squamosa. Another overlooked name, C. crinita Bertol., is shown to be the earliest name for C. evansii, but we propose to retain the latter through conservation. The typification of C. beaumontii Tuck. is amended. Cladonia conspicua is reinstated on the basis of new data. New range extensions in Canada and the United States are given for the poorly documented species C. oricola.

The distribution of projectile points over broad geographic areas yields important insights about Palaeoindian settlement pattern and history. While traditionally viewed as a Great Plains adaptation, the data show that fluted points are far more common in Eastern North America. These artefacts are not evenly spread across the landscape, furthermore, but occur in distinct concentrations. Within some of these areas distinct cultural traditions quickly emerged, something that appears tied to the sudden onset of the Younger Dryas.