Dispersal provided resilience to range collapse in a marine mammal: insights from the past to inform conservation biology.

Population loss is often a harbinger of species extinction, but few opportunities exist to follow a species' demography and genetics through both time and space while this occurs. Previous research has shown that the northern fur seal (Callorhinus ursinus) was extirpated from most of its range over the past 200-800 years and that some of the extirpated populations had unique life history strategies. In this study, widespread availability of subfossils in the eastern Pacific allowed us to examine temporal changes in spatial genetic structure during massive population range contraction and partial recovery. We sequenced the mitochondrial control region from 40 ancient and 365 modern samples and analyzed them through extensive simulations within a serial Approximate Bayesian Computation framework. These analyses suggest that the species maintained a high abundance, probably in subarctic refugia, that dispersal rates are likely 85% per generation into new breeding colonies, and that population structure was not higher in the past. Despite substantial loss of breeding range, this species' high dispersal rates and refugia appear to have prevented a loss of genetic diversity. High dispersal rates also suggest that previous evidence for divergent life history strategies in ancient populations likely resulted from behavioral plasticity. Our results support the proposal that panmictic, or nearly panmictic, species with large ranges will be more resilient to future disturbance and environmental change. When appropriately verified, evidence of low population structure can be powerful information for conservation decision-making.

Nanodiamonds in the Younger Dryas boundary sediment layer.

We report abundant nanodiamonds in sediments dating to 12.9 +/- 0.1 thousand calendar years before the present at multiple locations across North America. Selected area electron diffraction patterns reveal two diamond allotropes in this boundary layer but not above or below that interval. Cubic diamonds form under high temperature-pressure regimes, and n-diamonds also require extraordinary conditions, well outside the range of Earth's typical surficial processes but common to cosmic impacts. N-diamond concentrations range from approximately 10 to 3700 parts per billion by weight, comparable to amounts found in known impact layers. These diamonds provide strong evidence for Earth's collision with a rare swarm of carbonaceous chondrites or comets at the onset of the Younger Dryas cool interval, producing multiple airbursts and possible surface impacts, with severe repercussions for plants, animals, and humans in North America.

Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling.

A carbon-rich black layer, dating to approximately 12.9 ka, has been previously identified at approximately 50 Clovis-age sites across North America and appears contemporaneous with the abrupt onset of Younger Dryas (YD) cooling. The in situ bones of extinct Pleistocene megafauna, along with Clovis tool assemblages, occur below this black layer but not within or above it. Causes for the extinctions, YD cooling, and termination of Clovis culture have long been controversial. In this paper, we provide evidence for an extraterrestrial (ET) impact event at approximately equal 12.9 ka, which we hypothesize caused abrupt environmental changes that contributed to YD cooling, major ecological reorganization, broad-scale extinctions, and rapid human behavioral shifts at the end of the Clovis Period. Clovis-age sites in North American are overlain by a thin, discrete layer with varying peak abundances of (i) magnetic grains with iridium, (ii) magnetic microspherules, (iii) charcoal, (iv) soot, (v) carbon spherules, (vi) glass-like carbon containing nanodiamonds, and (vii) fullerenes with ET helium, all of which are evidence for an ET impact and associated biomass burning at approximately 12.9 ka. This layer also extends throughout at least 15 Carolina Bays, which are unique, elliptical depressions, oriented to the northwest across the Atlantic Coastal Plain. We propose that one or more large, low-density ET objects exploded over northern North America, partially destabilizing the Laurentide Ice Sheet and triggering YD cooling. The shock wave, thermal pulse, and event-related environmental effects (e.g., extensive biomass burning and food limitations) contributed to end-Pleistocene megafaunal extinctions and adaptive shifts among PaleoAmericans in North America.

Environmental imperatives reconsidered: demographic crises in western North America during the medieval climatic anomaly.

Review of late Holocene paleoenvironmental and cultural sequences from four regions of western North America show striking correlations between drought and changes in subsistence, population, exchange, health, and interpersonal violence during the Medieval Climatic Anomaly (A.D. 800-1350). While ultimate causality is difficult to identify in the archaeological record, synchrony of the environmental and cultural changes and the negative character of many human responses--increased interpersonal violence, deterioration of long-distance exchange relationships, and regional abandonments--suggest widespread demographic crises caused by decreased environmental productivity. The medieval droughts occurred at a unique juncture in the demographic history of western North America when unusually large populations of both hunter-gathers and agriculturalists had evolved highly intensified economies that put them in unprecedented ecological jeopardy. Long-term patterns in the archaeological record are inconsistent with the predicted outcomes of simple adaptation or continuous economic intensification, suggesting that in this instance environmental dynamics played a major role in cultural transformations across a wide expanse of western North America among groups with diverse subsistence strategies. These events suggest that environment should not be overlooked as a potential cause of prehistoric culture change.

The influence of body mass index and learned resourcefulness skills on body image and lifestyle practises.

We examined the importance of body mass index (BMI-light, medium, heavy) and learned resourcefulness skills (low, medium, high) on body image perceptions and lifestyle practises in 184 undergraduate women who were of relatively normal weight. Significant main effects were observed for the BMI and the learned resourcefulness variables. Supporting previous literature, the heavier and medium weight groups of women were more dissatisfied with their weight and appearance in comparison to the lighter weight group, but all groups shared similar eating attitudes and lifestyle practises. Also as predicted, women with low resourcefulness skills had more eating disturbances, perceived less control over their lifestyle, were more preoccupied with their weight in comparison to the high and, to a lesser extent, the medium groups. Contrary to prediction, heavier weight women with low resourcefulness skills were neither the most dissatisfied with their body shape nor the most susceptible to acquiring unhealthy lifestyle practises and disturbed eating attitudes. Implications for lifestyle counselors are discussed.

Importance of learned resourcefulness to weight loss and early success during maintenance: preliminary evidence.

The present study examined the importance of learned resourcefulness skills as measured by Rosenbaum's Self-Control Schedule (SCS) (Behav Ther 1980; 11: 109-121) to weight loss following a self-control program. Twenty-two women signed up for the 5-week self-control program. Participants' weight was recorded at the first and final session of the program, and at a 4-week follow-up. Results indicated that low resourceful women were more likely to drop out of the self-control program than high resourceful women. Although both the high and low resourceful women who completed the program lost the same amount of weight, only the high resourceful subjects continued to lose weight at follow-up. In contrast, the low resourceful women regained lost weight. Results point to the importance of learned resourcefulness for maintenance of weight loss following a self-control weight program.

Different mechanisms for social transmission of diet preference in rat pups of different ages.

We examined the role of simple exposure to a diet in the development of preference for that diet in rat pups 21, 28, 38, and 45 days of age. We found: that 21-day-old rat pups exhibited a preference for a diet to which they were simply exposed for 30 min; that 28-, 38-, and 45-day-old pups failed to exhibit simple-exposure induced preference for a diet; and that pups at all ages examined, exposed for 30 min to an anesthetized conspecific whose face had been dusted with a diet, subsequently exhibited a preference for that diet. We interpreted these data as indicating that socially-induced diet preference in 21-day-old pups can be explained by effects of simple exposure, while socially-induced diet preference in older rats cannot. Pups older than 21 days of age appear more sensitive to the social context in which diet-identifying olfactory cues are experienced than do 21-day-old pups.

A failure to find socially mediated taste aversion learning in Norway rats (R. norvegicus).

Observer rats interacted with conspecific demonstrators immediately after demonstrators ate a novel diet and were made ill by LiCl injection. Following their interaction with demonstrators, observers were tested for aversion to their ill demonstrator's diet. Previous research has shown that (a) an observer can extract information from a demonstrator sufficient to permit identification of the demonstrator's diet (Galef & Wigmore, 1983) and (b) a rat ill from LiCl toxicosis is an adequate unconditioned stimulus in a taste aversion learning paradigm (Lavin, Freise, & Coombes, 1980). Further, two of the present experiments demonstrated that cues emitted by a rat, reflecting the particular diet it has eaten, are an adequate conditional stimulus in a toxicosis-induced aversion learning situation. Observer avoidance of a diet previously ingested by an ill demonstrator was, however, not demonstrated. The implications of the failure to find socially mediated aversion learning are discussed.

Influence of oxytocin on human memory processes: validation by a control study.

An earlier report (1) of an adverse effect of high doses of oxytocin on human memory included results of studies on women receiving oxytocin as part of the treatment to induce 2nd trimester therapeutic abortion. These women served as their own controls. We have now been able to study a group of women who have been treated in all ways like the original group, with the exception that they did not receive oxytocin. The results from this external control corroborate the finding that oxytocin affected memory.