A molecular analysis of dietary diversity for three archaic Native Americans.

DNA was extracted from three fecal samples, more than 2,000 years old, from Hinds Cave, Texas. Amplification of human mtDNA sequences showed their affiliation with contemporary Native Americans, while sequences from pronghorn antelope, bighorn sheep, and cottontail rabbit allowed these animals to be identified as part of the diet of these individuals. Furthermore, amplification of chloroplast DNA sequences identified eight different plants as dietary elements. These archaic humans consumed 2-4 different animal species and 4-8 different plant species during a short time period. The success rate for retrieval of DNA from paleofeces is in strong contrast to that from skeletal remains where the success rate is generally low. Thus, human paleofecal remains represent a source of ancient DNA that significantly complements and may in some cases be superior to that from skeletal tissue.

A molecular analysis of ground sloth diet through the last glaciation.

DNA was extracted from five coprolites, excavated in Gypsum Cave, Nevada and radiocarbon dated to approximately 11 000, 20 000 and 28 500 years BP. All coprolites contained mitochondrial DNA sequences identical to a DNA sequence determined from a bone of the extinct ground sloth Nothrotheriops shastensis. A 157-bp fragment of the chloroplast gene for the large subunit of the ribulosebisphosphate carboxylase (rbcL) was amplified from the boluses and several hundred clones were sequenced. In addition, the same DNA fragment was sequenced from 99 plant species that occur in the vicinity of Gypsum Cave today. When these were compared to the DNA sequences in GenBank, 69 were correctly (two incorrectly) assigned to taxonomic orders. The plant sequences from the five coprolites as well as from one previously studied coprolite were compared to rbcL sequences in GenBank and the contemporary plant species. Thirteen families or orders of plants that formed part of the diet of the Shasta ground sloth could be identified, showing that the ground sloth was feeding on trees as well as herbs and grasses. The plants in the boluses further indicate that the climate 11 000 years BP was dryer than 20 000 and 28 500 years BP. However, the sloths seem to have visited water sources more frequently at 11 000 BP than at earlier times.

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.

Molecular coproscopy: dung and diet of the extinct ground sloth Nothrotheriops shastensis.

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.

Development of vegetation and climate in the southwestern United States.

Plant macrofossils in ancient packrat middens document the presence of woodland communities in most of the present Chihuahuan, Sonoran, and Mohave deserts in the southwestern United States during the late Wisconsinan (22,000 to 11,000 years before present by radiocarbon dating). Warm desert species were common in the woodlands at lower elevations and mixed conifer and subalpine forests were present at high elevations. Inferred mild, wet winters and cool summers produced unusual plant and animal associations compared to those of today. Montane communities acquired modern aspects and more mesophytic species disappeared from lower woodlands about 11,000 years ago. Early Holocene xeric woodlands and an inferred winter precipitation regime persisted until about 8000 years ago. The present circulation patterns, rainfall regimes, and biotic distributions probably formed as a result of the melting of the continental ice sheets. Southwestern communities appear to have responded quickly to climatic changes compared to the gradual responses of central and eastern United States forest communities.