Plant and animal species are not distributed randomly within the geographical areas where they can survive. Instead, 1 or several abundance peaks are found in the middle of a species' range, from which abundance gradually decreases toward the periphery of the geographic distribution. We found that the heterogeneity of the distribution of abundance for individual species decreased significantly with average abundance in neotropical migrant species, while no trend was found in temperate migrants. This relationship suggests that declines in the global population of neotropical migrant species may increase ''demographic fragmentation,'' so that areas of high abundance will be distributed in increasingly small and isolated pockets. Our analyses suggest the existence of 1 or more centers of abundance within the ranges of most species, the locations of which appear to be relatively stable over the few decades that continent-wide censuses have been available.
A diverse suite of fossils excavated at Laredo, Texas, gives a glimpse into the structure of an ancient tropical lowland forest-estuarine mangrove community that inhabited the Rio Grande Embayment >42 million years ago. Fossil pollen and megafloral remains document the presence of forest and swamp flora. Marine invertebrate species are represented by their shells and burrows. Teeth and bones of fishes, reptiles, and mammals attest to the presence of a diverse fauna that inhabited both aquatic and terrestrial environments. Several taxa belong to previously undiscovered genera and species and to 1 new family. Paleoecologic analysis indicates that climatic conditions resembled those found today in coastal areas of southeastern Mexico, northeastern Central America, and southern Papua New Guinea.
Two decades of systematic survey of ceramic sequences along the principal Amazonian tributaries enables comparison of territorial configurations, settlement size and permanence, village movement, and social organization of prehistoric and surviving indigenous groups. The surviving groups preserve a way of life established by the beginning of the Christian Era. Two general patterns are significant: The 1st rapid on all tributaries-dividing the nutrient-rich white water of the varzea from the nutrient-poor clear and black water of rivers draining the terra firme-also marks the boundary between distinct ceramic traditions. All local sequences exhibit discontinuities ca 1500, 1000, 700, and 400 BP, which imply replacement of the local population. The coincidence between these dates and mega-Nino events suggests the cause was severe subsistence stress provoked by catastrophic drought. These repeated dispersals explain the exceptionally heterogeneous linguistic and genetic distributions in Amazonia.
Analysis of the ranges of 67 Coleoptera species from the sub-Antarctic dominion of southern South America led to delimitation of 5 areas of endemism, namely Maule, Valdivian forest, Magellanic forest, Magellanic moorland, and Islas Malvinas (Falkland Islands). A cladistic biogeographic analysis of these areas was carried out, based on cladograms of the following 7 taxa: Creobius plus Cascellius (Carabidae); Eurymetopum modestum and maculatum species groups (Cleridae); Falklandius, Antarctobius, Germainiellus, and Anthonomus ornatus species group (Curculionidae). One general area cladogram was obtained applying the 3-area statements technique under both assumptions 0 and 1. According to this cladogram, the following sequence of area fragmentation could be hypothesized: (Maule (Valdivian forest (Islas Malvinas (Magellanic moorland, Magellanic forest)))).
Representations of the Amazonian river margin as a fertile plain are based upon models derived from the ecologies of whitewater rivers and should not be applied generally to the basin. In the nutrient-poor blackwaters of the northern section of the basin, flooding does not improve adjacent soils. There, it is the forest that restores the river. By reserving the natural vegetation of the riparian forest for fisheries maintenance and restricted harvesting, rather than deforesting the margin for agriculture, the Tukanoan Indians of the Upper Rio Negro basin in northwest Brazil demonstrate the potential of the forested floodplain as an important source of animal protein. Experimentation shows no comparable potential for agricultural production on blackwater soils.
Grand syntheses currently attempt to use cladistic models to show worldwide congruencies among linguistic, genetic, and archaeological data. In response, advocates of ethnogenetic theories are objecting to the application of cladistic models to human society. They argue that human societies are not necessarily analogous to biological species in the evolution of language and culture, and that amalgamation or creolization-rhizotic processes-is perhaps equally important. Linguists point out that human speech communities regularly borrows sounds, grammar, and vocabulary across profound ethnic barriers. By reference to demographic data, ethnologists show that intermarriage and genetic exchange are also a regular part of tribal life. Ethnogenetic theorists call for the construction of a range of evolutionary models to help interpret ethnic interaction.
Combining Landsat TM satellite data with ethnographic, botanical, and survey research allowed us to detect change between small areas of managed floodplain forest and unmanaged forest, and among 3 distinct age/growth classes of secondary succession following deforestation at both terra firme and estuarine sites in Brazilian Amazonia. Mechanized agriculture at one site has eliminated virtually all the mature upland forest. More diversified land use at another site shows a subtle cycling of flooded forest to managed palm forest in response to the price of palm fruit and cycling in the use of fallow land. A 3rd site, characterized by intensive colonization along the Transamazon Highway now consists largely of pastures degraded to various stages of secondary succession with crops constituting <4% of the total area. This study suggests how a balance between use and conservation in Amazonia may be achieved and the effectiveness of monitoring these types of land cover from satellite platforms.
Through archaeological research in the western Venezuelan savanna grasslands (llanos) we have investigated the development of pre-Hispanic chiefdoms encountered there by European explorers since the 16th century AD. Beginning ca AD 500 settlement hierarchies (as determined by site size and architecture) appeared on the savanna, accompanied by considerable population growth and social differentiation, regional networks of causeways, and intensive drained-field agriculture. Occupational sequences obtained from the llanos and adjacent piedmont of the upper Canagua River reveal differences in the scale and complexity of neighboring prehistoric societies and allow us to document their interregional exchange with distant groups and expansionist warfare.
This paper explores issues of pre-Hispanic Maya community organization. For decades Maya settlements were characterized as vacant ceremonial centers with large monumental edifices populated only by a handful of the priestly elite and a small dispersed peasantry. From this perspective, Maya centers were not true cities with complex social organization, occupational specialization, and large populations. Only after large-scale settlement-pattern studies in the 1960s documented thousands of ''house mounds'' at Lowland Maya centers did fundamental perceptions of Maya urbanism begin to change. The ceremonial-center concept has largely given way to a view of Maya centers as true preindustrial cities; many were sprawling settlements with sizable, socially complex populations that bustled with numerous and diverse activities.
This paper identifies 5 acculturation processes observable in Indian clothing from the Sierra Norte de Puebla: replacement, adaptation, introduction, innovation, and persistence. These distinctive phenomena clearly demonstrate that the process of costume change is not simplistic but rather is made up of many strands, each responding uniquely to culture contact situations, and each reflecting the different forces and processes that collectively make up 500 years of acculturation. We contend that clues in peasant clothing not only illuminate the shadowy history of such peoples, these garments also can provide insight into how the underlying elusive, complex acculturation process actually works.
''Problematic bedding-plane markings'' from the Appekunny Formation, described more than a decade ago, are now considered biogenic structures. Recent examination of these structures prompted a search for evidence of ancient metazoans in that formation. The results are not conclusive, yet some bedding-plane structures collected may be body fossils and others, trace fossils; they are not readily explained as nonbiologic sedimentary structures. Some of these structures could result from the activities of bacteria and algae. Confirmation of the animal origin of any of these obscure traces would effectively double the age of Metazoa on Earth.
In the hot and humid lowlands of southern Veracruz, the Olmec culture developed and flourished >3000 years ago. Among their accomplishments, they sculpted monolithic stone sculptures in many forms, such as colossal heads, thrones, and human and animal figures. At the Loma del Zapote site, in the hinterland of the early Olmec center of San Lorenzo Tenochtitlan, 4 Olmec sculptures were deliberately arrayed in an ensemble representing an ancient myth or event. Two nearly identical human sculptures and 2 felines were positioned on monumental architecture in a scenic display and left there. The display's significance combines cosmological and ceremonial messages with the power implicit in the pageantry of the setting.
Over the past decade, the informal economy of Peru has burgeoned in response to extreme economic and political crises. Despite the ubiquitous nature and increasing significance of this sector, remarkably little is known about it and its participants. Data I collected in a survey of street-vendors in 6 intermediate-sized Peruvian cities reveal that street-vending-the most visible informal occupation-is a deliberate activity undertaken by an increasingly large and significant segment of the urban population.
