Frugivory by extinct horses, gomphotheres, ground sloths, and other Pleistocene megafauna offers a key to understanding certain plant reproductive traits in Central American lowland forests. When over 15 genera of Central American large herbivores became extinct roughly 10,000 years ago, seed dispersal and subsequent distributions of many plant species were altered. Introduction of horses and cattle may have in part restored the local ranges of such trees as jicaro (Crescentia alata) and guanacaste (Enterolobium cyclocarpum) that had large mammals as dispersal agents. Plant distributions in neotropical forest and grassland mixes that are moderately and patchily browsed by free-ranging livestock may be more like those before megafaunal extinction than were those present at the time of Spanish conquest.

DNA from excrements can be amplified by means of the polymerase chain reaction. However, this has not been possible with ancient feces. Cross-links between reducing sugars and amino groups were shown to exist in a Pleistocene coprolite from Gypsum Cave, Nevada. A chemical agent, N-phenacylthiazolium bromide, that cleaves such cross-links made it possible to amplify DNA sequences. Analyses of these DNA sequences showed that the coprolite is derived from an extinct sloth, presumably the Shasta ground sloth Nothrotheriops shastensis. Plant DNA sequences from seven groups of plants were identified in the coprolite. The plant assemblage that formed part of the sloth's diet exists today at elevations about 800 meters higher than the cave.

We use national survey data to examine the extent to which various sources of political information expose people to dissimilar political views. We hypothesize that the individual’s ability and desire to exercise selective exposure is a key factor in determining whether a given source produces exposure to dissimilar views. Although a lack of diverse perspectives is a common complaint against American news media, we find that individuals are exposed to far more dissimilar political views via news media than through interpersonal political discussants. The media advantage is rooted in the relative difficulty of selectively exposing oneself to those sources of information, as well as the lesser desire to do so, given the impersonal nature of mass media.

Whatever the cause, it is extraordinary that dozens of genera of large mammals became extinct during the late Quaternary throughout the Western Hemisphere, including 90% of the genera of the xenarthran suborder Phyllophaga (sloths). Radiocarbon dates directly on dung, bones, or other tissue of extinct sloths place their ''last appearance'' datum at Ϸ11,000 radiocarbon years before present (yr BP) or slightly less in North America, Ϸ10,500 yr BP in South America, and Ϸ4,400 yr BP on West Indian islands. This asynchronous situation is not compatible with glacial-interglacial climate change forcing these extinctions, especially given the great elevational, latitudinal, and longitudinal variation of the slothbearing continental sites. Instead, the chronology of last appearance of extinct sloths, whether on continents or islands, more closely tracks the first arrival of people.