Consilient paleogenomic and archaeological data indicate that initial colonization by Paleoindian ancestors of living Native Americans occurred after 14,500 cal BP. Several recent finds raise the possibility that pre-Clovis people might have reached the Americas before 20,000 cal BP, but these precursors must have either failed to thrive, or were ultimately replaced by proto-Clovis or Clovis people. Ancient genomes show that divergent lithic traditions after 13,000 cal BP need not be attributed to a separate Pacific Rim migration stream.
Contrary to the alternative bolide impact theory, there is no evidence of a dramatic human population decline after 12,800 cal BP. Human hunting must have been involved, perhaps in concert with other indirect impacts.
In both North and South America, extinction of most genera of megafauna was virtually simultaneous with Paleoindian expansion. Fishtail points, derived from Clovis, mark the arrival and rapid expansion of Clovis-descended Paleoindians across South America, also evident in the sharp increase of radiocarbon dates, continent-wide, at 13,000–12,500 cal BP. The Anzick infant, buried with Clovis bifaces at 12,900 cal BP, belonged to a group that was ancestral to later Native Central and South Americans. 15–30% Ancient North Eurasian genes with those of East Asians. Ancient genomes now show that Native American ancestors were formed in Siberia or the Amur region by admixture of ca. The study of the peopling of the Americas has been transformed in the past decade by astonishing progress in paleogenomic research. Finally, we also provided calibration constraints for several anuran taxa. Additionally, we discussed issues directly related to those fossil occurrences, such as their temporal and geographic range, as well as the presence of putative biological and taphonomic biases. In total, we compiled 273 records, mostly anurans (~97.6%), followed by indeterminate caecilians (~1.4%) and urodeles (~1%). These materials come from 164 different fossil-bearing localities, spread over eight of the twelve South American countries, and range from the Early Jurassic to the Quaternary. Compared to the latest published reviews with similar scope, our results indicate that approximately 85.4% of the records correspond to specimens new to science or older ones that have been revisited. We used a mixed approach, both qualitative (with brief comments on each material) and quantitative (including scientometric parameters). peer-reviewed scientific papers, book chapters, monographs, and conferences abstracts). theses and dissertations) and published data (i.e. Here, we present the most comprehensive bibliographic review of fossil lissamphibians from South America to date, covering unpublished (e.g. This huge biodiversity is directly related to the complex geologic history of South America, which includes key events like the Gondwanan breakup, its isolation during parts of Mesozoic and Cenozoic, the Andean uplift, and the formation of the Panamá isthmus. Nowadays, lissamphibians are widely distributed in all continents, except Antarctica, but are particularly diversified in South America, where almost 3,000 species are found. We conclude that the obtained results do not support the Holocene survival of the megafauna in the Pampas.Īnurans, along with urodeles and caecilians are the extant representatives of the clade Lissamphibia.
In sum, they caused the degradation of collagen and the subsequent contamination by fulvic acids from the overlaying soil, which classic pretreatment techniques could not remove. The previously obtained Early Holocene ages of megafauna bones resulted from the interrelation of various factors as physical and chemical weathering, humification processes linked to pedogenesis, and diagenetic processes. In this article, we apply different methodological procedures (chemical, geoarchaeological and taphonomic analysis) in order to reconstruct the formation at the Campo Laborde the site and identify the processes and agents that affected its chronology. However, new dates from the same sample, purified from humates with XAD-2 resin, gave results of ~10,650 14C years BP. The combination of these factors has produced suspicious results, leading to the proposition of the Holocene survival in the region of the extinct Pleistocene megamammals such as the Megatherium Holocene ages from the Campo Laborde site. Many bone samples do not have collagen or have poor preservation giving collagen of questionably quality, in many cases it is contaminated by humic substances. Dating bone collagen has been problematic in the Argentinean Pampas.
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