Resumen de Initial human dispersal and native fauna at the South American southern cone, Argentina. An example case from the revision of the fossil collections
The scarcity of direct evidence as biological interventions (cut maks or carnivore marks) made difficult the discussion of how paleoecological relationships (e.g.. depredation an competition) should have been between humans, megaherbivores and carnivores during first humans’ dispersal in the Americas. To search this type of evidence in non-traditional archaeological sources, such as nineteenth collections of native fauna, is an alternative way to obtain information. This allows the understanding of how Homo sapiens has intervened in the established native ecosystem that has never been changed by hominid presence. First human dispersal in the Americas can be characterized as invasive, as this non-native species had a fast dispersion.
Taphonomy was used to differentiate biological interventions from other types of modifications. Considering the identified species with biological marks, humans should have depredate (or scavenge) over species that possessed defences to confront holartic carnivores (gigantism in Megatherium americanum case or armor in Glyptodontidae case). Smaller species of the megafauna, such as Mylodontidae, should have been exploited by carnivores and humans.
Therefore carnivores should have consumed some taxa of the megafauna in different moments of the Pleistocene period. This situation was sustained thought time despite environmental fluctuations. At the end of the Pleistocene, Homo sapiens entrance should have implied the addition of a new carnivore in the trophic chain. This new species had depredated over a major variety of fauna, even those ones not exploited by the native carnivores. Humans should have modified the existing ecological niches and colonized the empty ones affecting the established competition and depredation relationships. This provoked direct and indirect impacts in the native trophic chain. In long term, this situation should have affected the sustainability of this ecosystem.
